Issued June 25, 1909. 
 
 U. S. DEPARTMENT OF AGRICULTURE, 
 
 BUREAU OF, ANIMAL INDUSTRY. BULLETIN 112. 
 
 y*T 
 
 A. D. MELVIN, CHIEF OF BUREAU. 
 
 FHE LOCO-WEED DISEASE 
 OF THE PLAINS. 
 
 BY 
 
 C. DWIGHT MARSH, 
 
 Expert, Poisonous-Plant Investigations, 
 Bureau of Plant Industry. 
 
 WASHINGTON: 
 
 r,<>\ -\ -KNMI-NT PRINTING OFFICE. 
 
 1909.
 
 Issued June 25, 1909. 
 
 U. S. DEPARTMENT OF AGRICULTURE, 
 
 BUREAU OF ANIMAL INDUSTRY. BULLETIN -112. 
 
 A. D. MELVIN, CHIEF OF BUREAU. 
 
 THE LOCO-WEED DISEASE 
 OF THE PLAINS. 
 
 BY 
 
 C. DWIGHT MARSH, 
 
 Expert, Poisonous- Plant Investigations, 
 Bureau of Plant Industry. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 1909.
 
 THE BUREAU OF ANIMAL INDUSTRY. 
 
 Chief: A. D. MELVIN. 
 
 Assistant Chief: A. M. FARRINGTON. 
 
 Chief Clerk: CHARLES C. CARROLL. 
 
 Biochemic Division: M. DORSET, chief; JAMES A. EMERY, assistant chief. 
 
 Dairy Division: B. H. RAWL, chief. 
 
 Inspection Division: RICE P. STEDDOM, chief; MORRIS WOODEN, R. A. RAMSAY, 
 and ALBERT E. BEHNKE, associate chiefs. . 
 
 Pathological Division: JOHN R. MOHLER, chief; HENRY J. WASHBURN, assistant 
 chief. 
 
 Quarantine Division: RICHARD W. HICKMAN, chief. 
 
 Zoological Division: B. H. RANSOM, chief. 
 
 Experiment Station: E. C. SCHROEDER, superintendent; W. E. COTTON, assistant. 
 
 Animal Husbandman: GEORGE M. ROMMEL. 
 
 Editor: JAMES M. PICKENS.
 
 LETTER OF TRANSMITTAL. 
 
 U. S. DEPARTMENT OF AGRICULTURE, 
 
 BUREAU OF ANIMAL INDUSTRY, 
 
 Washington, D. C., January 16, 1909. 
 
 SIR : I have the honor to transmit herewith, for publication as a 
 bulletin of this Bureau, a manuscript entitled " The Loco-Weed Disease 
 of the Plains/' by Dr. C. Dwight Marsh, expert, of the Office of Poison- 
 ous Plant Investigations, Bureau of Plant Industry, being a report 
 of field investigations carried on during 1905, 1906, and 1907. 
 
 Although the work reported in this paper was done under the 
 supervision of the Bureau of Plant Industry, it has been considered 
 desirable, inasmuch as it deals largely with subjects coming within 
 the scope of the Bureau of Animal Industry, such as the symptoma- 
 tology, pathology, and treatment of a disease of animals, to have it 
 published as a bulletin of the latter Bureau. 
 
 For many years the so-called loco disease has been a cause of heavy 
 loss to the stockmen of the West, and it has been generally attributed 
 by them to certain plants eaten by the stock. As far back as 1886 
 the Bureau of Animal Industry investigated the subject, and an 
 article by Dr. M. Stalker in the Third Annual Report of the Bureau 
 has up to the present time remained the most satisfactory published 
 description of the disease. While Doctor Stalker in that report 
 expressed the belief that the loco plant "is possessed of some toxic 
 property that has a specific effect on the nerve centers," and while 
 these plants have long been classed as poisonous in the publications 
 of this Department, it has remained for Doctor Marsh in the work 
 herein reported to present experimental proof that the plants have 
 a poisonous effect and really cause the disease and to suggest a line 
 of treatment, and for Dr. A. C. Crawford, in Bulletin I'-".) of the 
 Bureau of Plant Industry, to discover and identify barium as a 
 poisonous clement in the plants. 
 
 Respectfully, A. 1). MKLVIX, 
 
 Chuf of Jiureau. 
 
 lion. JAMES WILSON, 
 
 Secretary of Agriculture.
 
 LETTER OF SUBMITTAL 
 
 U. S. DEPARTMENT OF AGRICULTURE, 
 
 BUREAU OF PLANT INDUSTRY, 
 
 Washington, D. C., July 10, 1908. 
 
 SIR: I take pleasure in handing you herewith, for publication as 
 a bulletin of the Bureau of Animal Industry, the accompanying manu- 
 script presenting a technical report entitled "The Loco- Weed Disease 
 of the Plains," prepared by Dr. C. Dwight Marsh, expert, working 
 under the direction of Dr. Rodney H. True, Physiologist in Charge of 
 Poisonous-Plant Investigations in the Bureau of Plant Industry. 
 
 This bulletin presents the evidence obtained from an experimental 
 field study of the relation of the so-called "loco weeds" to the losses 
 frequently attributed to the eating of them by horses, cattle, and 
 sheep. The plants studied are those characteristic of the plains, and 
 work has been carried on under actual field and corral conditions. 
 The investigation has been fully successful in proving the suspected 
 plants to be the cause of great and widely scattered stock losses. It 
 has made possible a satisfactory description of the disease and fur- 
 nishes a basis on which other disorders, now confused w T ith loco-weed 
 disease, but of different origin, may be distinguished from it. It has 
 developed a method of successfully treating a large percentage of 
 loco cases when such occur under circumstances making the frequent 
 handling of the animals practicable. 
 
 A companion bulletin, dealing with the technical laboratory studies 
 carried on at the same time in Washington by Dr. A. C. Crawford, 
 pharmacologist, is a necessary supplement to this bulletin for any- 
 one desiring a full account of the loco-weed disease. This bulletin is 
 entitled "Barium, a Cause of Loco- Weed Poisoning," and constitutes 
 Bulletin No. 129 of the series of this Bureau. 
 
 Respectfully, 
 
 B. T. GALLOWAY, 
 
 Chief of Bureau. 
 Dr. A. D. MELVIN, 
 
 CJtief, Bureau of Animal Industry. 
 
 4
 
 PREFACE. 
 
 The so-called "loco-weed disease" of horses, sheep, and cattle has 
 been a source of most serious complaint for many years, especially 
 from such stockmen as have grazed their animals on the Great Plains 
 east of the Rocky Mountains. While the losses have varied in severity 
 from year to year, they have reached such a magnitude as to make 
 the matter one of national concern. On account of both the eco- 
 nomic importance of the problem and of its intrinsic scientific inter- 
 est numerous investigations approaching the subject from the most 
 varied standpoints have been undertaken. As a net result there has 
 appeared a large body of literature marked by a wide diversity in the 
 conclusions reached. This discouraging state of disagreement pre- 
 vailed among the reported results of the field studies on the subject 
 prior to the time at which the Office of Poisonous Plant Investigations 
 undertook its campaign, but it was believed that by laying siege to 
 the problem in a more thoroughgoing and persistent way than any 
 of its predecessors had been in a position to do it might still be able 
 to ascertain the essential facts of the loco situation. 
 
 Accordingly, in 1905 a field station was established at Hugo, Colo., 
 in cooperation with the Colorado Agricultural Experiment Station, 
 which furnished the animals used, and experimental feeding work on 
 horses and cattle was begun. The state of opinion both among prac- 
 tical stockmen and among scientists had made clear the first step to 
 be taken. Popular opinion had long pointed to the eating of certain 
 members of the pea family (Leguminosae), especially Astragalus mol- 
 lissimus, the purple loco weed, and to Aragattus lamberti, the rattle- 
 weed, as the probable cause of poisoning. The first task was to test 
 the accuracy of this report. Accordingly feeding experiments under 
 field and corral conditions on plants of known origin were undertaken 
 at Hugo, and parallel laboratory tests were carried on at Washington. 
 The results showed clearly that loco symptoms were produced as a 
 result of loco-weed feeding, and as the investigation proceeded the 
 characteristics of this chronic, progressive disease were thoroughly 
 worked out. 
 
 The disagreement above referred to arose from a number of causes, 
 not least of which was the kind of animal upon which the investi- 
 gations had been carried out. Those working on sheep had seen 
 much reason to regard the symptoms observed as fully accounted 
 for by the various kinds of animal parasites with which this animal
 
 6 PKEFACE. 
 
 is affected in regions in which the loco disease has been regarded as 
 prevalent. Another reason for disagreement lay in the fact that the 
 characteristic symptoms of the loco-weed disease had not been sharply 
 presented as a result of the experimental production of the disease; 
 hence "loco" has been a general term covering many kinds of trouble 
 of a more or less chronic type. Indeed, there seems to be good reason 
 for believing that in some cases starvation has been called "loco." 
 Another source of confusion has lain in the fact that investigators 
 taking a more or less superficial view of the matter had seen animals 
 in various stages of the disorder and had not gone into the matter 
 deeply enough to correlate the different phases of a progressive disease. 
 
 The second stage of the field work looked forward to measures of 
 relief. The behavior of the plants concerned was looked into and 
 methods of eradication tried. Contrary to frequently expressed 
 belief, these weeds were found to be easy of extirpation by thoroughly 
 digging them out. Methods of meeting the trouble from the stand- 
 point of the animals concerned were in a degree worked out. 
 
 Laboratory work carried on at Washington seemed to show that 
 the loco plants coUected in the vicinity of the Hugo station and 
 doubtless those of eastern Colorado, Nebraska, and Kansas owe their 
 poisonous character, to a certain degree, to the presence in them of 
 barium absorbed from the soil. For a fair understanding of the loco 
 situation both the bulletin herewith presented, dealing with the field 
 phase of the work, and the companion publication on "Barium, a 
 Cause of the Loco-Weed Disease," based on the laboratory work, 
 must necessarily be taken into account. Unfortunately the nature 
 of these conclusions was not indicated until near the close of the 
 work for the season of 1907, so that the work in the direction of re- 
 medial measures gained no advantage from this information. Those 
 measures which were found to be most beneficial are shown, however, 
 by the light from the laboratory result, to be weU founded. The 
 field work has been carried out by Dr. C. Dwight Marsh, expert, and 
 his assistants, the laboratory work by Dr. A. C. Crawford, pharma- 
 cologist. 
 
 The present work by Doctor Marsh consists of a technical report on 
 prolonged field feeding investigations in connection with the loco 
 problem, carried out at Hugo and Woodland Park, Colo., and Im- 
 perial, Nebr., in cooperation with the Colorado Agricultural Ex- 
 periment Station and the Nebraska Agricultural Experiment Station. 
 Doctor Marsh has here succeeded in working out very completely and 
 more thoroughly than has ever been done heretofore the symptoma- 
 tology of the true loco disease, and has given a basis on which to 
 distinguish the trouble known as loco, properly speaking, from 
 various types of pseudo-loco which have gone under this name. He 
 has also described the plants which cause the trouble and outlined 
 their distribution.
 
 PREFACE. 7 
 
 The experiments intended to secure the extermination of the 
 plants are summarized, the conclusion of which is that the most 
 practicable way of disposing of the plants is to dig them out. This 
 can be done on land which is taken up by settlers, and will relieve a 
 large number of sufferers. The question of the open range, in so far as 
 it is still Government property, is one which we see noway of handling 
 except by Federal appropriation. 
 
 The treatment of animals is also outlined, it appearing that horses 
 and cattle require somewhat different handling. Horses are helped 
 by daily treatment with Fowler's solution, and cattle do best with 
 slight daily doses of strychnin, accompanied with laxative feed and 
 occasional doses of magnesium sulphate. Further work is planned on 
 wholesale antidoting under range conditions. 
 
 R. H. TRUE, 
 Physiologist in Cliarge, Poisonous-Plant Investigations, 
 
 Bureau of Plant Industry.
 
 CONTENTS. 
 
 Pago 
 
 PART I. INTRODUCTION 15 
 
 Historical summary and review of literature. 15 
 
 Symptoms mentioned in literature 32 
 
 Remedies proposed 33 
 
 Conclusions from literature . 34 
 
 Plants known as loco plants 36 
 
 List of Bpccies 36 
 
 Description of Aragallus lambcrli 37 
 
 Description of Astragalus mollissimus 38 
 
 Dispersal of Aragallus lamberli and Astragalus jnoU'i-ssimtis 3!) 
 
 Relations of loco plants to fertile soil 40 
 
 Experimental work limited to two plants , 40 
 
 PART II. EXPERIMENTAL WORK. 42 
 
 The problem to be solved 42 
 
 Plan of work 43 
 
 Location of experiment 43 
 
 Preliminary work 44 
 
 Work of the first season 45 
 
 Experiments with cattle 47 
 
 Experiments with horses 49 
 
 Cases of cattle and horses not subjects of experiment f>2 
 
 Summary of first season's work 54 
 
 Work of the second and third seasons 55 
 
 Experiments with cattle 56 
 
 Experiments with horses 02 
 
 Experiments with sheep 06 
 
 Discussion of sheep experiments 09 
 
 Experiment at Woodland Park, Colo 71 
 
 Experiment at Imperial, Ncbr 73 
 
 Remedial measures , 73 
 
 Treatment with strychnin in 1906 75 
 
 Treatment with arsenic in 1906 78 
 
 Results of treatment in 1906 81 
 
 Treatment of cattle in 1907 83 
 
 Treatment of horses in 1907 88 
 
 Treatment of sheep in 1907 90 
 
 PART III. RESULTS AND CONCLUSIONS 91 
 
 Cause of the disease 91 
 
 Symptoms of loco poisoning 92 
 
 Pathological lesions 95 
 
 Examination of blood 95 
 
 Walls of stomach 97 
 
 Hemolymph glands 97 
 
 Nervous system 97 
 
 9
 
 10 CONTENTS. 
 
 PART III. RESULTS AND CONCLUSIONS Continued. Page. 
 
 Virulence of loco poison 98 
 
 Time required to produce poisoning 98 
 
 Amount of loco necessary to produce poisoning 100 
 
 Relative importance of Astragalus mollissimus and Aragallus lamberti 101 
 
 Susceptibility of different breeds 102 
 
 Age susceptibility 102 
 
 Effect on animals other than horses, cattle, and sheep 103 
 
 Effect on man 104 
 
 Losses from loco poisoning 104 
 
 Destruction of loco weeds 105 
 
 Insects destroying loco plants 106 
 
 Effect of dry seasons 108 
 
 Remedies , 108 
 
 Treatment of cattle in 1907 110 
 
 Treatment of horses in 1907 110 
 
 General results of treatment Ill 
 
 Results with cattle Ill 
 
 Results with horses Ill 
 
 Permanency of loco cures Ill 
 
 Prevention of loco poisoning 112 
 
 Summary of work on remedies 112 
 
 GENERAL SUMMARY 113 
 
 BIBLIOGRAPHY i 117 
 
 INDEX . 127
 
 ILLUSTRATIONS. 
 
 PLATES. . 
 
 Page. 
 PLATE I. White loco, or rattle weed (Aragallus lamberti). Fig. 1. Plant in 
 
 flower. Fig. 2. Plant in fruit 38 
 
 II. Purple or woolly loco (Astragalus mollissimus) . Fig. 1. Flower 
 
 and fruit. Fig. 2. Habit of the plant 38 
 
 III. Fig. 1. Case 8, July 19, 1905. Just before the locoed condition 
 was particularly evident. Fig. 2. Case 8, August 3, 1905. 
 When animal showed typical symptoms of loco poisoning. 
 Fig. 3. Case 8, August 23, 1905. Emaciated condition of 
 the animal and typical loco attitude of lowered head and braced 
 legs. Fig. 4. Case 8, August 23. 1905. Loco leaping unneces- 
 sarily high in going over a rut in the road. Fig. 5. Case 8, 
 August 23, 1905. Lifting foot unnecessarily high in passing 
 over a wire. Fig.6. Case 8, August 27, 1905. Animal too weak 
 
 to stand unaided 50 
 
 IV. Fig. 1. Case 18, May 12, 1905. A mare weakened by loco poison- 
 ing. Fig. 2. Case 18, June 27, 1905. Advanced condition of 
 loco poisoning. Fig. 3. Case 19, May 16, 1905. Before eating 
 any of the loco weed. Fig. 4. Case 19, August 31, 1905. 
 Animal eating loco at a time when it has lost some flesh, but 
 was not in bad condition. Fig. 5. Case 19, October 15, 1905. 
 Animal in a very much reduced and emaciated condition. 
 Fig.6. Case 19, October 26, 1905. Animal just before its death. 50 
 V. Fig. 1. Case 524. Peculiar way in which a locoed horse uses its 
 mouth in attempting to eat. Fig. 2. Case 533. How a locoed 
 horse will rear when suddenly startled. Fig. 3. Case 525. 
 Peculiar gait which a badly locoed horse exhibits. Fig. 4. 
 Case 525. Horse rearing when suddenly startled by a hat 
 thrown out in front of it. Fig. 5. Case 529. A locoed angora 
 goat unable to get upon its feet, but otherwise fairly well. Fig. 
 
 6. Another attitude of case 529 50 
 
 VI. Fig. 1. Case 3, July 15, 1906. Effects of loco poisoning shown 
 in emaciation and dejected attitude just before death of ani- 
 mal. Fig. 2. Inner wall of fourth stomach of case 3, showing 
 
 ulcers u jxm its surface 58 
 
 VII. Fig. 1. Case 2, July 25, 1906. Steer bending low to avoid an 
 imaginary obstruction above it while passing through a gate. 
 Fig. 2. -Case 34. Another case similar to that in figure 1. 
 Fig. 3. Case 67, May 1, 1906. A bright heifer calf shortly after 
 birth. Fig. 4. Case 67, July 5, 1906. Calf showing effects of 
 loco which it had eaten in imitation of its mother. Fig. 5. 
 Case 67, October 16, 1906. Calf with typical symptoms of 
 loco. Fig. 6. Case 67, October 19, 1906. Animal just before 
 death 58 
 
 11
 
 12 ILLUSTRATIONS. 
 
 Page. 
 
 PLATE VIII. Fig. 1. Case 16, Juno 6, 1906. Horse before eating loco weed. 
 Fig. 2. Case 16, September 15, 1906. Animal in an advanced 
 stage of loco poisoning. Fig. 3. Case 52, May 19, 1906. Mule 
 in fairly good condition before feeding upon loco weed. Fig. 4. 
 Case 52, September 7, 1906. Last stages of loco poisoning. 
 Fig. 5. Case 50, July 19, 1906. An old horse before being 
 fed with the loco weed. Fig. .6. Case 50, September 18, 1906. 
 Effect of loco poisoning in attitude and emaciated condition; 
 also shows cute produced by running into a barbed-wire fence. . 66 
 IX. Fig. 1. A group of locoed sheep. Fig. 2. Sheep 27. A locoed 
 sheep in the last stages of poisoning. Fig. 3. Sheep 36. 
 Effect of loco poisoning combined with grub in the head. Fig. 
 4. Same as figure 3, different attitude. Pig. 5. Case 66, 
 October 20, 1906. A locoed lamb. Fig. 6. Case 66, Novem- 
 ber 12, 1906. Attitude of the animal just before its death 66 
 
 X. Fig. 1. Case 4, May 30, 1905. Before feeding on loco weed. 
 Fig. 2. Case 4, September 7, 1906. Showing typical symp- 
 toms of loco poisoning. Fig. 3. Case 4, September 15, 1906. 
 Animal under influence of loco and with a noticeable accu- 
 mulation of serous fluid under its chin. Fig. 4. Case 4, Au- 
 gust 22, 1907. Same animal in succeeding year, when it no 
 longer showed any symptoms of loco poisoning. Fig. 5. Case 
 536, July 9, 1906. A locoed steer with curvature of the fetlock 
 joints. Fig. 6. Case 536, July 25, 1906. The same animal 
 
 after treatment with strychnin 76 
 
 XI. Fig. 1. Case 547, April 23, 1907. A heifer in an advanced stage of 
 loco poisoning. Fig. 2. Case 547, August 22, 1907. Completely 
 recovered under treatment. Fig. 3. Case 551, June 14, 1907. 
 Ahorse in the advanced stages of loco poisoning. Fig. 4. Case 
 551, September 20, 1907. After course of treatment. Fig. 5. 
 Case 71, June 10, 1907. A locoed sheep, emaciated and ex- 
 tremely nervous. Fig. 6. Case 71, September 22, 1907. Re- 
 covered, as the result of the course of treatment 88 
 
 TEXT FIGURES. 
 
 FIG. 1. Distribution of Aragallus lamberti in the United States 37 
 
 2. Distribution of Astragalus mollissimus in the United States 39 
 
 3. Case 513. A locoed colt stunted in its growth by loco poisoning 44 
 
 4. Curve of weight of steer No. 10, 1906 58 
 
 5. Curve of weight of steer No. 10, 1907 ' 59 
 
 6. Curve of weight of cow No. 32 59 
 
 7. Curve of weight of cow No. 37 60 
 
 8. Curve of weight of calf No. 66 61 
 
 9. Curve of weight of calf No. 67 62 
 
 10. Curve of weight of calf No. 68 , 63 
 
 11. Curve of weight of horse No. 16 63 
 
 12. Curve of weight of horse No. 50 64 
 
 13. Curve of weight of horse No. 52 65 
 
 14. Curve of weight of horse No. 59 66 
 
 15. Curve of weight of steer No. 4, 1906 76 
 
 16. Curve of weight of steer No. 4, 1907 76 
 
 17. Curve of weight of steer No. 40.. 78 
 
 18. Curve of weight of horse No. 58 79
 
 ILLUSTRATIONS. 13 
 
 Page. 
 
 FIG. 19. Case 28, August 27, 1906. Locoed cow, but not a bad case 80 
 
 20. Curve of weight of cow No. 28, 1906 81 
 
 21. Curve of weight of cow No. 28, 1907 82 
 
 22. Curve of weight of steer No. 42, 1906." 84 
 
 23. Curve of weight of steer No. 42, 1907 84 
 
 24. Curve of weight of cow No. 35 85 
 
 25. Curve of weight of heifer No. 548 , 85 
 
 26. Curve of weight of steer No. 38 87 
 
 27. Curve of weight of heifer No. 547 87 
 
 28. Curve of weight of steer No. 555 88 
 
 29. Curve of weight of horse No. 551 89 

 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 PART I. INTRODUCTION. 
 
 HISTORICAL SUMMARY AND REVIEW OF LITERATURE. 
 
 The word "loco" is of Spanish origin, in which language it is used 
 both as a noun and as an adjective, meaning crazy. It has been 
 popularly applied to a considerable number of plants in the semiarid 
 region of the Western and Southwestern States because of the effects 
 these plants are supposed to produce on animals. 
 
 The first published account of the loco plants was by Doctor Vasey 
 in the monthly report of the Commissioner of Agriculture for October, 
 1873. He quotes a letter from O. B. Ormsby, of Bakersfield, Cal., 
 who describes the effect of the plant in the following terms : 
 
 It prevails quite abundantly over an extent of 150 square miles in this valley, and, I 
 am informed, is found in other valleys of the State, and also in Arizona. This year the 
 army-worm, and a minute insect which destroys the seeds, have killed a great deal of 
 it, but if not molested it will soon flourish to as great an extent as ever. I think very 
 few, if any, animals eat the loco at first from choice; but, as it resists the drought until 
 other feed is scarce, they are at first starved to it, and after eating it a short time ap- 
 pear to prefer it to anything else. Cows are poisoned by it as well as horses, but it 
 takes more of it to affect them. It is also said to poison sheep. As I have seen its 
 action on the horse, the first symptom of the poisoning, apparently, is hallucination. 
 When led or ridden up to some little obstruction, such as a bar or rail lying in the road, 
 he stops short, and, if urged, leaps as though it were four feet high. Next he is seized 
 with fits of mania, in which he is quite uncontrollable, and sometimes dangerous. 
 He rears, sometimes even falling backward, runs or gives several successive leaps 
 forward, and generally falls. His eyes are rolled upward until only the white can be 
 seen, which is strongly injected, and, as he sees nothing, he is as apt to leap against a 
 wall or man as in any other direction. Anything which excites him appears to induce 
 the fits, which, I think are more apt to occur in crossing water than elsewhere, and 
 the animal sometimes falls so exhausted as to drown in water not over 2 feet. deep. 
 He loses flesh from the first, and sometimes presents the appearance of a walking 
 skeleton. In the next and last stage, he only goes from the "l<x-o" to water and back, 
 his gait is feeble and uncertain, his eyes are sunken, and have a flat, glassy look, and 
 his coat is rough and lusterless. In general, the animal appears to perish from starva- 
 tion and constant excitement of the nervous system, but sometimes appears to suffer 
 acute pain, causing him to expend his strength in running wildly from place to place, 
 pawing and rolling, until he falls, and dies in a few minutes. 
 
 The specimen sent, Doctor Vnsey said, was an Astragalus. In the 
 report of the Commissioner of Agriculture for 1S74 Doctor Vasey 
 quotes this same letter of Ormsby and refers to other reports received 
 from California. The plants sent to him were determined as As- 
 
 15
 
 16 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 tragalus liornii Gr. and Astragalus lentiginosus Gr. He states, too, 
 in tliis report that Doctor Moffatt, of the United States Army, had 
 sent in specimens of Oxytropis lamberti, from Colorado, with the fol- 
 lowing description of its effects: 
 
 Cattlemen inform me that a weed grows among the grass, particularly in damp 
 ground, which is poisonous to horned cattle and horses and destroys many of them. 
 From the manner in which they describe its effects upon the animals it must be of 
 the nature of a narcotic, and they assure me that cattle, after having eaten it, may 
 linger many months or for a year or two, but invariably die at last from the effects of 
 it. The animal does not lose in flesh apparently, but totters on its limbs and becomes 
 crazy. While in this condition, a cow may lose her calf and never find it again and 
 will not recognize it if presented to her. The sight becomes affected, so that the ani- 
 mal has no knowledge of distance, but will make an effort to step or jump over a 
 stream or an obstacle while at a distance off and will plunge into it or walk up against 
 it upon arriving at it. The plant was pointed out to me, and seems to be related to 
 the lupin. 
 
 In 1875 Mr. Kellogg, in an article on California and Colorado loco 
 poisons, in the Proceedings of the Academy of Sciences of California, 
 states that thousands of horses, cattle, and sheep have been poisoned 
 by Astragalus menziesii in California. He gives a description also 
 of Oxytropis lamberti. 
 
 Professor Prescott in 1878 gave an account of the attempts of Miss 
 Watson to extract a poisonous principle from Oxytropis lamberti. 
 He states that Mr. Birdsall tried some of the ground root on himself, 
 but with little effect. 
 
 In an article in the American Journal of Pharmacy in 1879 Maisch 
 adds Astragalus moUissimus to the list of loco plants, and says that 
 he is informed that horses dig in the earth for it, become intoxicated, 
 seek water, drink with avidity, swell up, fall over, and die. 
 
 In the report of the Commissioner of Agriculture for 1878 Profes- 
 sor Collier refers to specimens of Oxytropis lamberti, which he says 
 were received for examination. He makes a brief reference to the 
 work of Miss Watson. 
 
 In 1880 Professor Collier, in the report of the chemist to the 
 Commissioner of Agriculture for 1879, makes a preliminary report 
 on Astragalus moUissimus and Oxytropis lamberti.' He states that 
 as a result of the analyses the only substances likely to be poisonous 
 hi Astragalus moUissimus are an alkaloid and a bitter extractive; 
 the harm being done by Oxytropis lamberti probably, by the fact 
 that the sweet taste of the plant leads the animals to eat a substance 
 which is mechanically unfit for food, but it is possible that if the 
 animal becomes enfeebled the small amount of alkaloids present 
 may produce poisonous effects. 
 
 Ott, in 1882, in an article in "New Remedies" states that the 
 loco plants are Oxytropis lamberti, Astragalus moUissimus, and 
 Sophora sericea. These. may prove fatal in two or three days; other
 
 REVIEW OF LITERATURE. 17 
 
 cases linger a year or more. Horses are more affected than cattle 
 or sheep. When first eaten an exhilarating effect is produced which 
 tempts the animal to eat more. Later the animal contracts the 
 habit. It does not acquire the habit in summer when there is an 
 abundance of grass. He then states that the effects are as follows: 
 
 1. A small amount of exercise will produce profuse sweating. 
 
 2. The animal when "shying", at an object is very liable to rear up and fall back- 
 ward. 
 
 3. A stroke, or even a touch, about the head seems to rouse the disorder, which is 
 immediately manifested by struggles and general frenzy. 
 
 4. While being ridden, when that is possible, the animal steps very high, as though 
 walking over obstacles, and the slightest thing in the road, as a stick, piece of rope, 
 or wagon rut, will be magnified into an apparently insurmountable difficulty, and it 
 is ludicrous to see the animal jump as though leaping over a ditch in an effort to get 
 over it. 
 
 5. The animal loses all power of reasoning or of coordination, will walk into a ditch 
 or bank instead of around it, and will sometimes walk backward when apparently 
 trying to go forward. 
 
 Ott made an alcoholic extract of Astragalus mottissimus and 
 treated subcutaneously frogs, rabbits, and a cat. The rabbits 
 were used for circulation tests. He summarizes the results of his 
 pharmacological tests as follows: 
 
 1. It decreases the irritability of the motor nerves. 
 
 2. It greatly affects the sensory ganglia of the central nervous system, preventing 
 them from readily receiving impressions. 
 
 3. It has a spinal tetanic action. 
 
 4. It kills mainly by arrest of the heart. 
 
 5. It increases the salivary secretion. 
 
 6. It has a stupefying action on the brain. 
 
 7. It reduces the cardiac force and frequency. 
 
 8. It temporarily increases arterial tension, but finally decreases it. 
 
 9. It greatly dilates the pupil. 
 
 In 1885 Mohr gives the distribution of the species, stating that 
 they are found in New Mexico, Colorado, Utah, Nevada, Arizona, 
 and California. He gives the following list of species as loco plants: 
 Astragalus mortoni, A. Jiornii, A. lentiginosus var. fremontii, A. 
 cocarjxi (oocarpa probably intended), A. crotalariir, and Oxi/tropis 
 lamberti. 
 
 Up to this time all reports agree as to the poisonous character 
 of the plants, but an anonymous author in the American Veterinary 
 .Review of 1885 states positively that the plant is not poisonous. 
 He says that when cattle eat a quantity it absorbs the juices of the 
 alimentary canal and dries them up. It then collects in the stomach 
 and intestines as a dry mass, and the pressure on the circulation 
 causes all the symptoms observable and finally produces death. 
 He declares that the internal condition of cattle with this disease 
 verifies this view. 
 
 79164 Bull. 11209 2
 
 18 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 Havard in 1885 says that Astragalus mollissimus is the loco plant 
 of western Texas. Animals avoid it, and eat it only through inad- 
 vertence or necessity. They lose appetite, become stupid and thin, 
 have tremors, and lose coordination. Oxytropis lamberti is found 
 only in northern Texas, and is nowhere common. 
 
 Hurd in 1885 states that the loco plants in California are Astragalus 
 crotalarise, A. lentiginosus , and Oxytropis lamberti. He says, too, 
 that animals eat loco only when driven by hunger, but they soon 
 crave it and 3 wander miles in search of it. They become intoxicated, 
 can not be led through a gate, walk mincmgly, shy, have an unsteady 
 gait, and become ataxic; when driven into water they may lie down 
 and refuse to rise. They become emaciated and finally die of exhaus- 
 tion. Complete recovery never occurs. 
 
 In the Cornhill Magazine of 1886 there is an article entitled, "The 
 cowboy at home," in which is a somewhat detailed description of 
 the phenomena 01 loco poisoning in horses, as follows: 
 
 We passed a heap of about 40 dead horses piled up together, the most revolting, 
 pitiful spectacle imaginable, and standing listlessly, or moving about with staggering 
 gait, were about twice as many more still living creatures with a peculiar look and 
 manner about them such as I had never seen before, and most of whom must surely 
 soon be dragged to the big heap close by. But what on earth did it all mean? It 
 seemed so strange suddenly to come across this grewsome sight on the lone prairie. I 
 soon learned the explanation. 
 
 A weed called "loco" has of late years largely increased in some of the cattle ranges 
 of Texas and the Indian Territory, owing, probably, to an increase in the rainfall. It 
 has a mysterious habit of appearing suddenly in places where it was before unknown, 
 and, given a dry season, of as suddenly disappearing. During the summer, when the 
 prairie is a fair expanse of waving grass, lit up with bright flowers, both horses and 
 cattle instinctively avoid it, but when in the fall of the year the grass becomes scarce 
 in overstocked regions, and when all around assumes a brown and burnt r up appear- 
 ance, it stands out conspicuously and temptingly green, its long, soft, velvety leaves 
 rising in a bunch from 6 inches to a foot off the ground. Then the hungry creatures 
 begin by nibbling, suspiciously and stealthily, at the seductive plant, but very soon 
 become reckless, and eagerly and greedily devour all that comes in their way. And 
 now, if the mania can not be nipped in the bud by a sufficiency of good strong food, 
 the animal is doomed, for he has become a confirmed "loco-eater." He will rapidly 
 become thin and lose all control over his movements; he will be subject to frequent 
 fits, during which he lies on the ground groaning and foaming at the mouth; he throws 
 himself about without reason; rears up or runs about in small circles when you attempt 
 to mount him; his eyes turn dull and stupid; in short, he gives you the impression of 
 being bereft of his senses. Specimens of loco have been subjected to analysis by ex- 
 perts in Washington and in Edinburgh, but without anything injurious being dis- 
 covered in it. It is possible that some minute animalculse may be the cause of the 
 mischief, but up to the present its disastrous effects only are known, for this pernicious 
 weed causes periodically the death of thousands of horses and cattle. 
 
 Professor Sayre, of the University of Kansas, in 1886 published 
 in the Transactions of the Kansas Academy of Sciences a somewhat 
 extended account of loco and locoed animals. He visited New 
 Mexico, Colorado, and Kansas, and states that the plant appears at
 
 REVIEW OF LITEKATUBE. 19 
 
 Medicine Lodge and extends southwesterly into the Indian Territory 
 and northwesterly through Kansas. He says that a veterinary sur- 
 geon, Doctor Harding, took two horses with a taste for loco, and kept 
 one in a pasture with loco and the other in a loco-free pasture, with 
 the result that the one died and the other recovered. Two others 
 were fed, one with hay and the other with dead loco. The first one 
 lived and the second died. He gives a description of the symptoms 
 of locoed animals, the result of his personal inquiry among ranchmen 
 and the report of a Mr. R. E. Steele. It is somewhat interesting, 
 however, that many parts of this description agree word by word, 
 and sentence by sentence, with a letter of Mr. Ormsby quoted in 
 Vasey's report of 1873. 
 
 Sayre states that the loco disease is due to two plants, Astragalus 
 niollissimus and Oxytropis lamberti. He made a preliminary chemical 
 examination which was apparently never completed. lie also held 
 an autopsy on a locoed cow belonging to Mr. Steele. The cow was 
 undersized, poor, stupid, unsteady, with short breathing and shaking 
 head. lie reports that the reticulum and psalterium were softened. 
 The tissues through the intestines were degenerated ; the peritoneum 
 and the omentum were inflamed with tumors the size of a pea; the 
 heart was one-third larger than normal, with the mitral and tricuspid 
 valves inflamed; the bile was thin and watery, and the inner coat 
 of the bladder softened; the membranes of the brain were congested 
 and adherent, the brain was paler than normal, and the membranes 
 of the spinal cord were inflamed and adherent. He concludes that 
 the disease is one of the mucous and serous membranes. 
 
 In the same year Professor Sayre published an article in the report 
 of the Kansas State board of agriculture, which was, to a large extent, 
 a repetition of the material published in the Transactions of the 
 Kansas Academy of Sciences. lie adds, however, a report that the 
 plant causes abortion in cows. He states that as the result of his 
 own chemical examination it would appear that there is no poisonous 
 principle in the plant, and suggests that the hairs upon the leaves may 
 be irritating. 
 
 In the Third Annual Report of the Bureau of Animal Indnstrv /or 
 1SSO Doctor Stalker gives a report of a personal investigation of the 
 loco disease. He visited the country from western Nebraska to 
 Salt Lake, and from Cheyenne to El Paso. He describes the appear- 
 ance and habits of the two plants, ()jri/tro]>in Idinbcrti and Afttmyalufi 
 nioUitstsiinuti. He states that the term loco is used simplv to desig- 
 nate a certain disease, as well as being a term applied to plants. 
 
 lie found that the loco habit is an acquired one and that animals 
 will forget it when kept on loco-freo food. All confirmed loco-raters 
 become complete physical wrecks, showing general derangement 
 of the nervous system and more or less digestive disturbance. In
 
 20 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 post-mortem examinations of horses he found a serous effusion in 
 the lateral ventricles, hemorrhagic clots in the fourth ventricle, and 
 sometimes a serous effusion in the arachnoid space. The liver was 
 dense in structure. Immense numbers of bots were found, especially 
 in the duodenum, and he suggests that while these parasites would 
 not account for the clinical symptoms, they may have something to 
 do with the abnormal appetite. In post-mortems on sheep large 
 numbers of tapeworms were found, and these he suggests may account 
 in part for the loco appetite in sheep. He presumes that the plant 
 is possessed of some toxic property that has a specific effect on the 
 nerve centers, and that these effects have a marked tendency to 
 remain permanent, though he was not aware that the poison, if 
 present, had ever been separated by analysis. He states that the 
 disease may be cured by taking animals from the range and feeding 
 them on nutritious diet. He also states that special attention 
 should be given to the destruction of intestinal parasites, and ex- 
 presses his belief that thousands of supposed cases of loco poisoning 
 are the result alone of such parasites. 
 
 In 1887 Behr, in an article on the poisonous plants indigenous to 
 California, states that the notorious loco weed is an Astragalus, but 
 that the exact species is not known with certainty. He says that 
 dogs, cats, and rabbits do not suffer if the seeds or herbs are mixed 
 with their food, and that cattle, sheep, and horses suffer only at cer- 
 tain seasons. Poisoning may be due either to infection by some 
 fungoid parasite, perhaps of the Claviceps order, or by a substance 
 produced by fermentation or putrefaction, or it is possible that the 
 poison may not be of vegetable origin at all, but caused by some 
 parasite infesting the suspected plant. 
 
 Carhart, in the New York Medical Record in 1887, speaks of his 
 acquaintance with the effects of loco in the Panhandle. Cattle 
 occasionally eat it, but are rarely affected by it; mules do not suffer 
 from it; but cow ponies die by the thousand. If the taste is acquired 
 they will leave green grass to hunt for it. They break down rapidly, 
 become weak, staggering, foolish, and crazy. ^ A tap on the head 
 will cause them to stagger, rear, and fall backward. Vision is im- 
 paired, and there is a loss of muscular coordination. The Indians say 
 that it is due to an insect, but the author has found none. Carhart 
 drank a decoction of loco without effect, and administered the decoc- 
 tion to a locoed horse with apparent good results. 
 
 In the Homeopathic Recorder in 1887 Doctor Gee gives a somewhat 
 detailed account of some experiments made by some of his students 
 who took doses of loco extract. There seems to be no uniformity 
 in the reports that these students made. They tell of an infinite 
 number of symptoms, many of which, apparently, must have been 
 imaginary.
 
 REVIEW OF LITEEATUEE. 21 
 
 Dr. T. E. Wilcox, of the United States Army, writes to the Medical 
 Record in 1887 on the subject of loco, and states that the treatment 
 employed by the cowboys in Idaho consists in the amputation of the 
 tails of the animals affected. They claim that they seldom lose any 
 stock when this treatment is instituted early enough. The writer 
 adds that paralysis is probably due to congestion of the spinal co i 'd. 
 It affects the posterior members first. The pupils are dark, as after 
 the use of eserin. Oxytropis lamberti, Astragalus mollissimus, and pos- 
 sibly others of the Leguminosae are charged with producing loco poi- 
 soning. In Idaho the cowboys call these plants, larkspur, although 
 true larkspur is rarely found in the line of march and at that season of 
 the year. 
 
 Kingsley in 1888 refers to Kennedy's-work, which was at that time 
 unpublished, and gives cases of locoed mules, with report of a post- 
 mortem. In a second letter he concludes that the mules suffered 
 from colic, and this, from his report of the symptoms and the post- 
 mortem, would seem to be probable. He concludes that the loco plant 
 is not poisonous and that the symptoms and pathology are such as 
 would result from overfeeding with any green feed. 
 
 Kennedy in 1888, after a description of the plant, tells of his at- 
 tempts at analysis. He discovered no alkaloid and separated no 
 poisonous principle. He experimented with infusions in boiling 
 water, with dried powder, and with an organic acid separated from 
 the plant. He fed these materials to a dog and there was no effect. 
 He concludes that the plant is not poisonous and that ill effects, if any, 
 are produced by the tough, fibrous, indigestible character of the plant 
 acting as a foreign body, or else its action is identical with an overload 
 of any kind. 
 
 The St. Louis Medical and Surgical Journal in an editorial article a 
 little later refers to Kennedy's work, and criticizes him for trying 
 physiological experiments on a dog rather than on an herbivorous 
 animal, and considers his results of no value. 
 
 Klencli in 1888 gives a general description of symptoms, referring 
 to the papers of Say re and Stalker, and advises as remedies the admin- 
 istration of potassium bromid or belladonna and aloes, and bleeding. 
 
 In 18S8 Miller writes of the geographical distribution of Oxytropis 
 lamberti and Astragalus mollissimus and gives a description of the 
 plants. His description of the effect of the weeds, as well as his 
 remarks in regard to the distribution, are apparently derived from 
 Sayre's publications. He makes the suggestion that inasmuch ns 
 loco is said to produce abortion it may be that the plant might be used 
 as an emmenagogue. 
 
 Say re in 1888, in a paper published in the Kansas State board of 
 agriculture report, adds to what he has written in preceding papers a 
 summary of the results of Kennedy and of Ott, and states that he
 
 22 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 has tried the extract on himself, but with no result. In the same year, 
 in the Proceedings of the Kansas Pharmaceutical Association, he 
 "reports what he has written before and seriously questions the exist- 
 ence of poisonous properties in the plants, considering that the 
 effects may be due to malnutrition, brought about in part by feeding 
 on this weed. 
 
 Schwarzkopff in 1888 published his experience with locoed ani- 
 mals in Texas, detailing the symptoms in very much the same terms 
 as those used by previous authors. He used as a remedy atropin 
 and morphia sulphate applied hypodermically. The horse was quiet 
 and acted sensibly in six days. He reports a post-mortem on another 
 horse. He found the cranial sinuses filled with a straw-colored fluid, 
 the vessels of the pia mater injected, and the gray substance reddened 
 and edematous. On the base of the brain inside the arachnoid 
 membrane he found a teaspoonful of pinkish fluid. The medulla 
 and cord were edematous and moist on cut surface. 
 
 In 1889 McEachran reports an autopsy near Livermore, Colo. He 
 watched 100 cases of locoed sheep at Givens Ranch, near Colorado 
 Springs, and made post-mortem examinations of two, no details of 
 which are published with the report. 
 
 In 1889 Anderson describes the symptoms of locoed animals. He 
 says that the animal has unnaturally bright eyes, froths at the 
 mouth, exhibits extreme salivation, or sometimes the mouth may be 
 hot and dry. The appetite is lost and an offensive gas is belched 
 forth. The animal loses control of the limbs, and sometimes the 
 muscles of the neck are contracted on one side. It becomes stupid, 
 falls, and rarely rises again. It may die in a few hours or lie for a 
 week. He reports a post-mortem in which the intestines and sur- 
 rounding fat were green immediately after death. The arteries and 
 smaller vessels in the limbs were gorged with thick dark blood. 
 The lining of the first stomach was worn and ulcerated in patches 
 and in some cases decomposition seemed to have commenced ; it was 
 very soft and could be peeled off the muscular layer in big pieces. The 
 lungs and heart were almost bloodless, and the brain was purplish, 
 soft, and pulpy. He states, however, that the symptoms vary in 
 different cases. He lists as loco plants Oxytropis lamberti, Leucocri- 
 num montanum, Fritilla.iia pudica, and ZygaJenus elegants. 
 
 In 1889 Dr. Mary G. Day, in two articles in the New York Medical 
 Journal, describes the process which she followed in attempting to 
 separate a poison from loco plants and gives the result of some phar- 
 macological experiments with a decoction. She fed the decoction to a 
 cat and found disturbing sj^mptoms in two days. There was less 
 activity, the coat became rough, the appetite was lost, fondness for 
 loco was induced, and there was diarrhea, retching, and vomiting. 
 Emaciation increased until the eighteenth day, when convulsions
 
 REVIEW OF LITERATURE. 23 
 
 occurred. There were alternate periods of excitement and quiet for 
 36 hours, when the posterior extremities became paralyzed, and the 
 animal died in about two hours. The post-mortem examination 
 showed ulcers in the stomach and duodenum. The heart was in 
 diastole and anemic. In the second case she found similar symptoms 
 but no periods of excitement. This cat died on the thirteenth day. 
 Two cats were confined and treated in the same way, except that one 
 was fed loco. The loco-fed animal acquired the disease, while the 
 other remained well. In Michigan experiments on frogs and kittens 
 caused nervous twitchings and death. A jack rabbit was fed on milk 
 and grass, then fresh loco was substituted for the grass. It acquired 
 the habit and died in ten days, with the head thrown back and with 
 the stomach ruptured. Doctor Day states that more poison is pres- 
 ent in the plants in the fall and winter. She reached the following 
 conclusions : 
 
 1. There is some poison in loco weed which may cause the illness, and, if sufficient 
 quantity is taken, the death of an animal. 
 
 2. This poison is contained in the decoction obtained from the plants, and by sys- 
 tematically feeding it to healthy cats cases of loco disease may be produced. 
 
 3. A taste for the green loco weed may be experimentally produced in the jack 
 rabbit. 
 
 4. From the large quantity of the plant or of the decoction required to produce the 
 disease, the poison must be weak, or, if strong, it must be in very small amount. 
 
 In the Druggists' Bulletin of 1889 is a resume of the work on loco up 
 to that date. Miss Day's work is criticized as valueless because of the 
 lack of control experiments. The article is generally skeptical in 
 regard to the existence of a specific poison in the loco plant. 
 
 In 1889 Power reported upon a chemical examination of loco, 
 and later, in 1891, Power and Cambier made another report. The 
 general result of their work was negative. They showed both in 
 Astragalus and Crotalaria a very small amount of toxic alkaloids. 
 
 In 1889, in the Druggists' Bulletin, Professor Sayre reviews his 
 preceding work in regard to the loco plants, gives drawings of two 
 species, Oxytropis lamberii and Astragalus moUissimus, and reports 
 the detail of a chemical examination of these plants. lie also states 
 that he has performed certain physiological experiments, but does 
 not report them in this paper. lie gives quite fully the result of 
 the work of Doctor Ott, and then states that his own physiological 
 experiments have all given negative results. He does not claim 
 that the weed is not poisonous, but apparently does make the claim 
 that nothing is proven as yet in regard to its poisonous properties. 
 
 Curtice, in 1889, in his report upon the animal parasites of sheep, 
 quotes the report of the autopsy by Faville on locoed sheep, in which 
 he found numbers of ttcnite. The author says that the description 
 of locoed sheep applies equally well to those infested with tjrniic; 
 that it is difficult to separate the symptoms of the two diseases, and
 
 24 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 many cases of locoed animals are victims of tapeworms. That the 
 taeniae may tend to produce depraved appetites or the morbid craze 
 for particular food is also a reason for suspecting that the loco disease 
 may depend in part on the tapeworm disease. 
 
 Sayre, in 1890, in the report of the Kansas board of agriculture, 
 gives the result of Miss Day's paper, in which she tells of the separa- 
 tion of crystals which she considered the poisonous principle. Sayre 
 produced the same crystals and considers them inorganic. He says 
 he himself has separated a crystalline organic substance but has not 
 carried the investigation further. 
 
 An article by Pammel, in 1891, states that Astragalus moUissimus 
 and Oxytropis lamberti are called loco plants by ranchmen. Crota- 
 laria is the cause of loco in Iowa. In Australia a species of Gompho- 
 lobium is a loco. He adds, also, as loco plants Malvastrum coccineum 
 and Physostigma venenosum. He does not distinguish any difference 
 in the specific effects of Astragalus and Aragallus. He also calls 
 Stipa viridula a loco weed. 
 
 In 1892 McCullaugh gives a description of the pathological effects 
 in locoed horses. He says that all herbivorous animals, even ante- 
 lopes, are liable to the disease. The disease was first noticed west 
 of the Rio Grande years ago. Since then the weed has been 
 carried by birds and the continuity of the wind to the upper Mis- 
 souri, into old Mexico, the Gulf of California, and California. The 
 action of the plant is similar to that of alcohol or opium. The weed 
 becomes green while the snow is on the ground. Among the first 
 symptoms are loss of flesh, general lassitude, and impaired vision. 
 The last may be taken as the first symptom. After the animal begins 
 to become viciously shy an exostosis appears in the middle and supe- 
 rior portion of the frontal bone, becoming at times as large as a 
 pullet's egg, and remains permanently. The animal exists in this 
 condition from ten to eighteen months, but sometimes it will live not 
 over three months. As the disease advances the animal loses mus- 
 cular power and tetanic symptoms appear. It will invariably fall if 
 suddenly startled. The muscles of the mouth and tongue become 
 partially paralyzed, so that it is impossible to take food. The author 
 has many times offered water to locoed horses that he knew had not 
 drunk in five or six days. They would sometimes gaze stupidly for 
 hours at a time at a trough of water, but make no attempt to drink. 
 The true cause of death is starvation. 
 
 In 1892 Sayre, in the Thirteenth Report of the Kansas board of 
 agriculture, after a resume of his previous papers, states that he has 
 been able to separate an alkaloid, but that it was not poisonous, and 
 his conclusions are that there is a disease having a mysterious con- 
 nection with Astragalus and allied genera. He quotes a letter from 
 Professor Harshbarger, of Topeka, which states that animals hunt
 
 REVIEW OF LITERATURE. 25 
 
 loco, become nervous and later crazy ; that they bite at water instead of 
 drinking it, their eyesight becomes affected, and they become vicious 
 and emaciated. Sayre then gives Harshbarger's opinion in regard to 
 loco, which is skeptical and negative. He suggests that the disease 
 may be caused by other things, as hot weather or stagnant water. 
 
 He also quotes a letter from Mr. Mayrath, of Dodge City, who 
 states that he had 18 cattle eating loco in November, and that all 
 died before May 1, although well fed. He says that cattle and horses 
 eat loco for the most part in the late^fall and winter; that they eat 
 it grubs, eggs, and all. He suggests a connection of the grubby stem 
 with the disease, and says he has been told of a man who was killed 
 inside of twenty-four hours by loco tea. 
 
 Sayre then gives a resume of Doctor Mayo's paper, and in conclu- 
 sion gives an instance of a horse having loco disease, although it had 
 never seen the loco plant. 
 
 Schuchardt, in 1892, in the Deutsche Zeitschrift fur Thiermedicin, 
 has an article on the loco disease of horses and cattle, in which he 
 gives a careful and accurate resume of the literature up to date, but 
 adds nothing to what has been said in earlier publications. 
 
 In the same year Dr. B. F. Stalker, in the Medical Current, Chicago, 
 states that as early as 1849 the Indians along the Missouri River told 
 of a plant found in Kansas, Texas, and along the foothills as far 
 north as Wyoming which would produce death, preceded by erratic 
 forms of excitement. They said it affected cattle and horses, and 
 the Mexicans claimed a similar effect on man. The author describes 
 Astragalus mollissimus and Oxytropis lamberti, and states that abortion 
 is sometimes produced by eating loco. 
 
 O'Brine, in 1893, in a bulletin of the Colorado State Agricultural 
 College, gives a review of preceding literature, quoting especially from 
 Faville. In 1889 Astragalus mollissimus and Oxi/trojns lamberti were 
 fed to a sheep at the college, with no results. He states that the Colo- 
 rado law offering a bounty for the destruction of loco plants was 
 passed March 14, 1881, and repealed in April, 1885. It cost the State 
 $50,000 a year. 
 
 O'Brine tried to separate the poisonous principle, and failed. He 
 found the same reactions for alfalfa that he obtained for loco. lie 
 made tests with rabbits, with no results. He made a number of 
 autopsies near Livermore, and 'found a clot at the base of the brain 
 in all cases. lie suggests that the effects of the loco are not direct, 
 but dependent upon some digestive processes. 
 
 Williams, in 1893, in the bulletin of the South Dakota Agricultural 
 College, gives a list of the plants supposed to cause loco in South 
 Dakota. They include Astragalus mottissimus, A. lotiflorus, A. l>i- 
 sulcatus, A. haydeniensis, and Oxytropis lamberti. He describes the 
 plants and general effects on the stock, quoting Vasey and Mayo.
 
 26 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 In 1 893 Professor Mayo published a general article on the subject of 
 loco, in which he not only described the symptoms in much the same 
 terms as former authors, but gave the results of some personal 
 examinations of his own. He says that the old inhabitants of south- 
 western Kansas say it is more abundant upon ranches where Mexican 
 sheep were pastured in an early day. He found on the roots two 
 species of Tineidae, and upon the plant a Bruchus and a Curculionid. 
 He tried extracts of the dried plant and the fresh leaves on guinea 
 pigs, but with no results. Both guinea pigs and cattle refused to eat 
 the plant. He ate it himself with no ill effects, and concluded that 
 the weed was not the cause of the disease, but when he made observa- 
 tions in the field he changed his mind. He found that animals 
 acquire a taste, wander off alone, lose flesh, and have a stiff and 
 stilted action of the legs. When lying down, they have difficulty in 
 rising, the head trembles, the dependent parts of the body swell; they 
 have a vacant stare, though they are not blind, and they do not shed 
 their hair in the spring. They can be led only with great difficulty, 
 shy violently, and are subject to crazy fits, especially when driven 
 hard. Locoed animals never fully recover. 
 
 In post-mortems he found a large amount of serum in the body 
 cavity, the intestines atonic, spleen small, liver small, pale, and ad- 
 herent to the diaphragm. The rumen was full of loco. The menin- 
 ges of the brain were thickened and congested. The brain was 
 smaller than normal, and firmer, and the gray tissue was darker than 
 normal and thinner on the cerebrum. In the central white substance 
 of one brain were three small gelatinous translucent spots about the 
 size of a small pea. Sections of the brain showed atrophy. Pur- 
 kinje's kidney cells in some cases had disappeared ; in other cases the 
 processes were atrophied. There were no changes in the spinal cord. 
 His conclusion was that there was no evidence of a narcotic principle 
 in the plant, and that the animals died from malnutrition or mal- 
 assimilation produced by eating the loco plants. The cause of the 
 delirium may be clots or thrombi in the brain, as these are apt to be 
 formed during wasting and debilitating diseases. He suggests as 
 treatment removing the animals from loco plants and giving them 
 some good condition powders. 
 
 In the Medical Century of 1893 Doctor Givens writes on the sub- 
 ject of loco, or "crazy weed," or Astragalus moUissimus. He de- 
 scribes the plant in general and the effect upon animals of eating, 
 much as had already been described by preceding authors. He then 
 states that he had secured from Colorado some of the dried root of 
 Astragalus moUissimus, from which he prepared a tincture and tested 
 its effect when given as a medicine upon three cases of insanity, each 
 of which had hallucinations of sight and hearing. The net result of 
 his investigations was that loco has no effect on insane patients, and
 
 REVIEW OF LITERATURE. 27 
 
 there is no reason to think that it can be used to advantage in the 
 treatment of mental disorders. He concludes that it is harmless, 
 even when taken in large doses, although it may at the same time 
 have a poisonous action on herbivorous animals, as claimed by 
 others. 
 
 In the report of the Canadian Experimental Farms in 1893 Fletcher 
 mentions the fact that the subject of loco weeds has been brought 
 to their attention by the poisoning of sheep and lambs in Manitoba, 
 and suggests that owners of herds should send in specimens of the 
 plants in order that the reports may be verified. 
 
 W. Thornton Parker, in 1894, describes the symptoms of loco 
 poisoning as seen by him in Texas and New Mexico. Describing the 
 plant, which seems to have been Astragalus mollissimus, he suggests 
 that beneficial results can be obtained by treating the affected 
 animals with muriate tincture of iron with accessories of hygienic 
 treatment. 
 
 In the same year Professor Mayo describes much more fully than 
 in his earlier article, and very accurately, the symptoms of loco 
 poisoning. He speaks of the dropsical swellings which sometimes 
 occur in the dependent parts of the body. Locoed animals walk 
 with a peculiar creeping gait that is recognized by those familiar witli 
 the disease. No pojsonous principle was found, and he reiterates his 
 former conclusion that the loco disease is the result of malnutrition. 
 
 In 1895 Kuedi reports an examination of supposed locoed sheep in 
 Estes Park, Colo. He found their temperatures low between 86 
 and 100 F. with breathing stertorous, pulse slow, abdomen dis- 
 tended, and diarrhea present. In the autopsies he found them anemic, 
 the intestines filled with gases, the liver enlarged and filled with 
 blood, the kidneys congested, and the bladder distended. The heart 
 was in diastole and the brain bloodless. He prepared solutions and 
 fed rabbits. All passed through a period of excitement which the. 
 author explains as caused by the brain anemia, followed by a period 
 of dullness. They were observed for a period of ten days. None 
 died, but they were killed for autopsy. In all cases there was 
 congestion of the abdomen and anemia of the brain. He separated a 
 base which he called "locoin" and an acid, and states that locoin is 
 not poisonous, but that the acid is. He refers to the loco as "white 
 loco" or Astragalus moUiftfrimus. It is difficult to tell what species he 
 was dealing with, but it seems more likely that it was Arafjattuf* 
 lamkerti. It may be said in regard to his work that there seems to be 
 no evidence that the sheep examined by him had eaten loco, and the 
 symptoms and the autopsies lead the present author to conclude that 
 they did not have the loco disease at all. 
 
 In 1896 Nocholds, in the American Veterinary Review, gives his 
 experience while driving a bunch of horses from southern to north-
 
 28 THE LOCO- WEED DISEASE OP THE PLAINS. 
 
 western Texas. Some of them gradually acquired the loco habit. 
 One of them wandered from the bunch, walked high, had a staring 
 coat, glassy eyes, and could not be driven. Some of them showed 
 the effect only when excited or driven hard. All were stupid. All 
 affected animals were mares over 6 years old, and 23 out of 300 died 
 within a year. The author thinks there is no cure. 
 
 In 1897 Mr. J. IT. Maiden, in the Report of the Department of 
 Agriculture of Sydney, New South Wales, in a discussion of poisonous 
 plants in that locality, mentions the " indigo disease" of Australia as 
 probably identical with the loco disease of the United States, and in 
 connection with this he quotes O'Brine in regard to the loco disease. 
 
 In 1898 Professor Sayre published in the Kansas Medical Journal a 
 repetition of his former statements, and concludes with this state- 
 ment: T 'We feel warranted in saying that the so-called poison is a 
 development within the animal, and not a product preexisting in the 
 weed itself." 
 
 In 1899 Prof. S. B. Nelson, of the Washington Agricultural College, 
 in a report on experiments on feeding wild plants to sheep, states that 
 he has fed small amounts of Astragalus spaldingii, Astragalus palou- 
 sensis, and Astragalus dorycnioides, but without any bad results. 
 
 In the Annual Report of the Department of Agriculture of the 
 Northwest Territories in 1899, T. N. Willing refers to the abundance 
 of Oxytropis lamberti in the Territories and expresses his surprise 
 that there is not more trouble from it. 
 
 In an article on the ethno-botany of the Coahuila Indians of 
 southern Calif ornia, Barrows in 1900 refers to the genus Astragalus, 
 known as "rattlesnake weed" or "loco weed" in California. He 
 says that several species are poisonous to cattle, sheep, men, and 
 horses. One species, he states, is used by the Coahuila Indians as 
 a flavoring principle, and according to another author dry pods are 
 pounded up and mixed with beans and perhaps other articles of food 
 as a spice. 
 
 In Law's work on veterinary medicine, published in 1901, is a 
 general review of the subject of loco, concluding with a special report 
 of Miss Day's work. 
 
 In the Annual Report of the Bureau of Animal Industry for 1900 
 E. V. Wilcox states that Astragalus spicatus is the most important 
 loco plant of Montana. Besides this species there are Astragalus 
 splendens and Astragalus lagopus, which are harmful. He disproves 
 the belief that the loco disease may be caused by alkali, and gives 
 an account of the characteristics of the disease and the details of an 
 acute case of a sheep which died in four days. He states that the 
 disease in cattle is rare. In autopsies on sheep a slight congestion 
 of the brain is noticed, the fatty tissue is reduced, and the muscles
 
 REVIEW OF LITERATURE. 29 
 
 pale. Locoed sheep may be fed and fattened for mutton, but 
 never fully recover from the disease. 
 
 In the report of Chesnut and Wilcox on stock-poisoning plants 
 of Montana, in 1901, is a discussion much like that in the preceding 
 paragraph. They state that the most reliable observations on the 
 subject of loco disease indicate that it is the result of eating undue 
 quantities of certain weeds, and express the belief that the plants 
 contain a poisonous principle which is harmful to domestic animals. 
 They report two experiments, feeding a Belgian hare and a sheep 
 with extract of loco, but without results except slight narcotic 
 effects in the rabbit. 
 
 In 1901 Mr. Maiden repeats the statements made in 1897 in the 
 
 Report of the Department of Agriculture of Sydney, and a-dds that 
 
 in all probability the "nenta disease" of South Africa is identical 
 
 -with the "pea-eating disease" of Australia and the loco disease of 
 
 the United States. 
 
 In the report of the Oklahoma Agricultural Experiment Station 
 -<of 1902 are some brief statements in regard to loco. Loco is dis- 
 tributed over the western half of the territory and causes considerable 
 loss. 
 
 In the Proceedings of the Pacific Northwest Wool Growers' Asso- 
 ciation of 1902, Professor Blankinship tells briefly about the effects 
 of eating Oxytropis lamberti and gives its distribution in Montana. 
 He states particularly that the loco habit is taught to one animal 
 by another. Hence, he says, it is very important that animals 
 that have commenced to eat the weed should be separated from 
 the rest of the herd. 
 
 T. N. Willing, in the Annual Report of the Department of Agri- 
 culture of the Northwest Territories in 1902, gives a cut of Astra- 
 galus lamberti and says that A. lamberti and A. splendcns are abun- 
 dant from Manitoba to the Rockies. He gives a short description of 
 the symptoms of loco poisoning. Cattle are seldom affected. 
 
 In 1903 Professor Blankinship, in a bulletin of the Montana Agri- 
 cultural Experiment Station on loco and some other poisonous 
 plants, treats rather fully of loco in Montana. He states that the 
 loco plant in Montana is the Oxytropis Idmberii Pursli., or Astraga- 
 lus spicatus (Hook.) Rydb. Aftor referring to the distribution of 
 the plant generally, ho says that in Montana it is found up to an 
 altitude of 8,000 feet in the country east of the Continental Divide, 
 between Livingston on the west and Billings on the east, the moun- 
 tains on the south, and north to the vicinity of the Little Belt and 
 Highwood Mountains. Sheep are the principal sufferers from loco 
 in Montana, horses and cattle boing rarely affected, and it is the 
 young sheep and colts that are affected rather than the older ones.
 
 30 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 He then describes the symptoms of the disease, and, taking up the 
 subject of prevention, reasons that because it is the younger animals 
 that are principally affected, especial care should be taken of them. 
 In regard to the extermination of the plant, he says it is possible to 
 accomplish this by digging it out, as has been proved in one or two 
 specific cases. This should be done when the plant is in bloom in 
 order to kill the seed crop. 
 
 In 1903, Van Es and Waldron, of the North Dakota Experiment 
 Station, in an article entitled "Some Stock Poisoning Plants of North 
 Dakota," give a general description of the symptoms of loco poison- 
 ing which adds nothing to that of previous publications. They state 
 that the loco plants are Aragallus lamberti and AragaUus splendens, the 
 former being generally distributed in the State, while the latter occurs 
 on more sterile soil and is reported only from a few counties of the 
 State. Neither plant has caused any large amount of damage in 
 North Dakota. 
 
 In- 1904 Sayre published two papers. In the first, entitled "What 
 is Insanity in Lower Animals?" he suggests that the symptoms of 
 loco disease may be due to anemia, cerebral congestion, inflammation 
 of the brain or its membranes or of the membranes enveloping the 
 spinal cord, or to forage poisoning. In his second paper, published 
 in the Journal of the Kansas Medical Society, he gives an analysis 
 to determine the food value of the loco plant, but does not discuss 
 the results of the analysis. In this paper he broaches as theories to 
 explain the effect of loco, (1) irritation by hairs; (2) disturbance to 
 digestion, such as might happen from any food in a weakened condi- 
 tion of the animals in spring; and (3) a. poison developed in the 
 process of digestion. 
 
 In 1904 J. E. Payne, of the Agricultural Experiment Station of 
 Colorado, in a report on cattle raising on the plains, states that there 
 is no evidence that cattle eat largely of the loco weed or are affected 
 by it. Where these plants are prevalent the range is very poor. He 
 further says that the talk about loco is kept up by cattle owners to 
 keep out settlers. A number of unnamed diseases may be included 
 under the term "loco." 
 
 In 1904 Doctor Marshall published in the Johns Hopkins Hospital 
 Bulletin a resume of the results of his work of the preceding two 
 years, while in the service of the United States Department of Agri- 
 culture, in feeding locoed sheep in Montana. His conclusions may 
 be summarized as follows: The loco disease affects horses and sheep, 
 and occasionally cattle and goats. Astragalus moUissimus and Ara- 
 gaUus spicatus are the commonest loco weeds. Ranchers consider as 
 important accessory factors: (1) Age; the disease appears before the 
 end of the second year; (2) insufficient feed; (3) insufficient supply
 
 REVIEW OF LITERATURE. 31 
 
 of water; lack of salt; (4) general conditions of health; healthy 
 animals never acquire the disease. He then describes the symptoms. 
 
 In this investigation only sheep were examined; all were lambs or 
 yearlings. They did not prefer the loco. Many had bronchitis, con- 
 junctivitis, etc. Usually the fleece was rough. All were infected 
 with parasites. The parasites found were Thysanosoma actinioides, 
 flaemonchus sp. (in the fourth stomach), Metastrongylus flaria (in 
 the bronchioles), Sarcocystis tenella (in the muscles), and Oysticercus 
 tenuicollis (in the peritoneal cavity). The fringed tapeworm was so 
 abundant as to dilate the bile ducts. 
 
 He concludes that there is no true loco disease of sheep produced 
 by the weed, but that the so-called locoed animals suffer from bad 
 feeding, insuflicient care, and a variety of other diseases, the most 
 important of which are the parasitic diseases. 
 
 Fletcher in 1905, in evidence given before the committee on agri- 
 culture and colonization at Ottawa, Canada, stated that the loco 
 weeds were abundant in Alberta and through to Manitoba, but are 
 not as injurious as in Montana. He has never seen a case of loco 
 disease in Canadian-bred animals. 
 
 In 1905 Professor Linfield, director of the Agricultural Experiment 
 Station of Montana, in a report of a series of experiments on sheep 
 feeding, compares the effect of feeding upon a flock of locoed sheep 
 with the effect produced upon a flock of normal sheep. He states as 
 his general results that the locoed sheep gained about as much as the 
 normal sheep, but inasmuch as they were very thin at the start, it 
 took about twice as long to get them ready for market. All these 
 locoed sheep were treated with a vermifuge at the beginning of the 
 experiment, and the author implies that their locoed condition may 
 have been the combined result of poor feed and parasites. His work 
 may be criticized, inasmuch as his figures as to gain in weight are 
 based on the surviving locoed animals. He started with 42, and only 
 29 remained at the end of the experiment. lie states that nearly 
 half of this lot was lost through natural death or by killing for post- 
 mortem examinations. The fact, however, remains that his figures 
 are based on the best of the flock, and the statistical results of the 
 feeding experiment would probably not have appeared as favorable 
 for the locoed animals if the whole number hail been considered. 
 
 Again, in 1905, in the Proceedings of the Kansas Academy of 
 Sciences, Sayro published a partial bibliography of the subject and 
 repeated the report of the analysis and his theory of the causation of 
 the disease by irritation by the hairs of the plant. 
 
 Prof. L. G. Carpenter, director of the Agricultural Experiment 
 Station of Colorado, in the eighteenth annual report of the station 
 (for 1904-5) states that considerable work has been done by Payne
 
 32 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 on the subject of loco, which has made clear the necessary conditions 
 of the experiment. He also refers to the cooperative work undertaken 
 with the United States Department of Agriculture. 
 
 In this same publication Dr. George H. Glover, veterinarian of the 
 Colorado Agricultural Experiment Station, gives a partial report upon 
 the first year's cooperative work at Hugo. 
 
 Prof. S. B. Nelson in 1906 reports feeding small quantities of 
 Astragalus spaldingii, A. arrectus, A. pursMi, and A. reventus, but 
 with no results. He suggests that longer feeding might have produced 
 more positive results. 
 
 Prof. L. G. Carpenter, in the report of the Colorado Agricultural 
 Experiment Station for 1906, published in 1907, gives a resume of the 
 work done by the United States Department of Agriculture at Hugo. 
 
 Doctor Glover, in a report of the veterinarian to the director of the 
 Colorado Experiment Station, published in 1907, makes a brief state- 
 ment also in regard to the work at Hugo. 
 
 SYMPTOMS MENTIONED IN LITERATURE. 
 
 In the preceding pages we find noted a very large number of 
 symptoms of loco poisoning. The list below gives most of these, 
 omitting those found by Doctor Gee in his experiment on his class, 
 as they were almost infinite in number as well as contradictory. In 
 this list the symptoms are arranged purposely in such a manner as to 
 show their contradictory character. 
 
 Congestion of abdomen. 
 
 Abortion. 
 
 Anemia. 
 
 Loss of appetite. 
 
 Arteries gorged with thick, dark blood. 
 
 Bile thin and watery. 
 
 Bladder with inner coat softened. 
 
 Bladder distended. 
 
 Blindness. 
 
 Body cavities with an excess of serous 
 fluid. 
 
 Brain atrophied. 
 
 Brain bloodless. 
 
 Brain with the membranes inflamed. 
 
 Brain congested. 
 
 Pia mater injected. 
 
 Gray tissue of brain darker than 
 normal. 
 
 Gray substance of brain red and 
 edema tous. 
 
 Brain tissues soft and pulpy. 
 
 Sinuses of brain filled with fluid. 
 
 Lateral ventricles of brain holding 
 serous effusion. 
 
 Fourth ventricle of brain with blood 
 clot. 
 
 Breathing short. 
 
 Coat rough. 
 
 Winter coat retained. 
 
 Constipation. 
 
 Diarrhea. 
 
 Convulsions. 
 
 Craziness. 
 
 Hallucinations. 
 
 Lack of muscular coordination. 
 
 Emaciation . 
 
 Exostosis of frontal bone. 
 
 Eyes glassy. 
 
 Eyes dull and staring. 
 
 Pupils dilated. 
 
 Vision impaired. 
 
 High temperature. 
 
 Low temperature. 
 
 Frothing at the mouth. 
 
 Shaking head. 
 
 Impaired hearing. 
 
 Heart of increased size. 
 
 Heart with inflamed valves.
 
 SYMPTOMS AND REMEDIES. 
 
 33 
 
 Heart bloodless. 
 
 Heart with reduced action. 
 
 High stepping. 
 
 Hyperesthesia. 
 
 Intestines filled with gases. 
 
 Intestines congested. 
 
 Intestines green. 
 
 Intestines with tissues degenerated. 
 
 Kidneys congested. 
 
 Purkinje's cells in kidneys lacking. 
 
 Difficult to lead. 
 
 Liver dense. 
 
 Liver small. 
 
 Liver enlarged. 
 
 Lungs bloodless. 
 
 Narcotized. 
 
 Stiff neck. 
 
 Irritability of motor nerves. 
 
 Decrease of irritability in sensory 
 nerves. 
 
 General derangement of nervous 
 system. 
 
 Paralysis of mouth or tongue. 
 
 Paralysis of hind legs. 
 
 Omentum inflamed, with tumors. 
 
 Rearing and plunging. 
 
 Shying. 
 
 Solitary habit. 
 
 Spinal cord edematous. 
 
 Spinal cord membranes inflamed and 
 adherent. 
 
 Spleen small. 
 
 Excitement followed by depression. 
 
 Stomach ruptured. 
 
 Third stomach (psalterium) softened. 
 
 Second stomach (reticulum) softened. 
 
 First stomach (rumen) lining worn, 
 ulcerated, and decomposed. 
 
 Swelling under the jaw. 
 
 Swelling of dependent parts of body. 
 
 Te'eth loose. 
 
 Teeth not loose. 
 
 Tremors. 
 
 Tendency to turn either to the right or 
 to the left but not in both directions. 
 
 Urine offensive. 
 
 Vomiting. 
 
 Weakness across loins. 
 
 Weakness and staggering gait. 
 
 While this list is confusing because of the number of items and the 
 contradictions involved, yet in regard to some of the symptoms there 
 is great uniformity. The following symptoms have been noted by a 
 large number of observers, and in regard to them there is a fairly 
 general agreement: 
 
 Slow, staggering gait. 
 Rough coat. 
 Staring look. 
 Emaciation. 
 
 Lack of muscular coordination. 
 Extreme nervousness, shown in shying, 
 rearing, etc. 
 
 REMEDIES PROPOSED. 
 
 The remedies suggested for the loco disease by different writers, as 
 would be expected from the indefinite knowledge of the subject, have 
 been of various kinds, many of them having no logical basis. Among 
 them are the following: 
 
 1. Potassic bromifl, belladonna, and bleeding. 
 
 2. Amputation of the tail, which, of course, i simply one form of bleeding. 
 
 It. Potassium iodid and qiiinin, with strychnin; in some cases it may be desirable 
 to add jaboiundi or pilocarpin. 
 
 4. It lister on the top of the head with the administration of GO grains of calomel 
 every second or third night. The calomel should be followed by sulphate of iron. 
 
 5. A prescription of belladonna, calomel, licorice, and glycerin. 
 
 6. A prescription of iron sulphate, gentian, muriate of ammonia, and potassic 
 nitrat<>. 
 
 79154-Bull. 11209 3
 
 34 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 7. In acute cases, permanganate of potash, sulphate of ammonia, morphine as an 
 antispasmodic. In chronic cases, remedies to affect the stomach, as common salt, 
 hydrochloric acid, and gentian root. 
 
 8. Muriate tincture of iron with hygienic accessories. 
 
 CONCLUSIONS FROM LITERATURE. 
 
 From the foregoing review of the literature we may deduce the 
 following conclusions: 
 
 1. There is a disease common among horses, cattle, and sheep in 
 the semiarid region of the West, the animals affected showing these 
 characteristics: Slow, staggering gait, rough coat, staring, vacant 
 look, and emaciation. They have hallucinations, can not be led or 
 backed, show more or less lack of muscular coordination, gradually 
 lose flesh, and die. They show a hypersensitive condition of the 
 nerves, so that if a horse affected with loco disease is suddenly startled 
 he may rear and fall over backward. Cattle show less pronounced 
 symptoms, but in general are affected like the horses. The char- 
 acteristic of a locoed steer is the shaking head, together with the 
 other nervous phenomena. To these symptoms may be added some 
 others upon which there is no general agreement. 
 
 2. The cause of this disease is quite uniformly ascribed by the 
 stockmen to plants known by them as loco plants, of which the prin- 
 cipal ones are Astragalus mollissimus and Aragallus lamberti. Similar 
 properties are ascribed to other closely allied species in Montana, 
 Wyoming, Arizona, and California. 
 
 3. Scientific investigations of the subject have led to very contra- 
 dictory results. 
 
 It will be noticed from the review of the literature that in the 
 chemical and pharmacological examination Prescott got no positive 
 results. The same is true of the experiments made by Gee. Ken- 
 nedy found no poisonous principle and fed the loco to a dog with no 
 results. Day got from the extract fed to cats definite loco symp- 
 toms, and similar results from her experiment with a jack rabbit. 
 The work of Power and Cambier led to only negative results. Sayre 
 made numerous experiments on himself and animals, and has reached 
 the general conclusion that the weed possesses no poison. It will be 
 seen that the only positive proof of the poisonous character of the 
 plant was obtained by Doctor Day. The preponderance of laboratory 
 tests made up to the time that the Bureau of Plant Industry under- 
 took its investigations was, therefore, against the poisonous character 
 of the plant. 
 
 The results of the study of locoed cattle, horses, and sheep in the 
 field are no more conclusive. . The reports of post-mortems show 
 few lesions common to all cases, or even to any considerable number 
 of them. There is a fairly general agreement as to some abnormal
 
 CONCLUSIONS FROM LITERATURE. 35 
 
 condition of the brain and the nervous system, but so far as the other 
 organs of the body are concerned, the reports do not agree with each 
 other. There seems to be a general feeling of skepticism among 
 those who have seen cases in the field as to the actual poisonous 
 properties of the plants. The following have been suggested . as the 
 possible causes of the disease: 
 
 1. Starvation. 
 
 2. Irritation of the stomach by the hairs of the leaves. 
 
 3. Penetration of the* stomach by the sharp hooks of the seed pods. 
 
 4. The loco absorbs the juices of the stomach, collects as a dry mass, causes pressure 
 upon the circulation, and finally death. 
 
 5. The formation of balls in the stomach from sand taken in when the grass is short 
 (bezoars), and the consequent irritation and inflammation due to the presence of this 
 foreign substance. 
 
 6. Impaction of the intestines by twigs, etc. 
 
 7. Fermentation of the materials in the stomach. 
 
 8. Tapeworms. 
 
 9. Other parasitic worms. 
 
 10. Eggs or bots. 
 
 11. Trypanosomes. 
 
 12. Some poisonous principle in the plants. 
 
 To these possible causes might be added some suggestions made by 
 stockmen which have little foundation. It is generally known that 
 the loco plants are attacked by a considerable number of insect 
 enemies, of which more will be said later. Among them are certain 
 insects whose larvae live in the roots and stems of the plants and have 
 been noticed for a great many years by the stockmen. Many of the 
 stockmen consider that these "worms," as they call them, are con- 
 nected directly or indirectly with the loco disease. Some of them state 
 that the eggs of the worms are taken into the body of the animal, hatch 
 out there, and live in the alimentary canal; evidently confounding the 
 ordinary parasitic worms of animals with these insect larviv. ('. 1). 
 Steele, in Farm and Ranch, in 1901, suggests that these "worms" 
 consume the food in the stomach and thus produce starvation. One 
 correspondent of our ofliee has elaborated an interesting theory to 
 this effect: That the cattle and horses eat the loco plants upon which 
 are the worms, as he calls them, and the eggs of the worms. These 
 eggs hatch out in the stomach of the locoed animal and crave loco for 
 their own food, and it is to supply food to satisfy this craving of t he- 
 worms that the horse or the steer frantically seeks loco. 
 
 It will bo remembered that Sayre in his 1904 paper broaches three 
 distinct theories: (1) Irritation by hairs; (2) disturbance of diges- 
 tion, such as might have been caused by any food in the weakened 
 condition of the animals in the spring; and (3) a poison developed in 
 the process of digestion. 
 
 Marshall's investigations led him to conclude that the loco plant 
 was not the direct cause of the disease and that many cases of so-
 
 36 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 called loco disease were really caused by animal parasites. This 
 seemed particularly probable in the case of sheep, which all through 
 our western region are infested with (Estrus ovis and with TJiysa- 
 nosoma actinioides, as well as certain other animal parasites. 
 
 It will be seen that the loco problem up to the time when the re- 
 view of this literature closed was an open one, with the presumption 
 in faA r or of the nonpoisonous character of the plant, and in taking 
 up the investigation of this subject it seemed necessary as the first 
 step to determine positively whether the loco plants were really the 
 cause of the so-called loco disease. 
 
 PLANTS KNOWN AS LOCO PLANTS. 
 
 A large number of plants have been known as loco plants. The 
 following list is taken from the literature on the subject. It is to 
 be presumed that there have been some errors in determination, 
 but the length of the list shows that loco is a term which has been 
 applied quite widely. By general agreement, however, the term, 
 outside of California, New Mexico, and Arizona, is now rather gen- 
 erally confined to the two species, Aragallus lamberti and Astragalus 
 mollissimus. In some localities the term "loco" is confined to Astra- 
 galus mollissimus, but this is generally in places where Aragallus 
 lamberti is comparatively rare. 
 
 LIST OF SPECIES. 
 
 Amarantus albus. 
 Astragalus bigelovii Gray. 
 Astragalus crolalaria. 
 
 (=A. oocarpus Gray.) 
 Astragalus dorycnioides. 
 
 (=A. succumbens Dougl.) 
 Astragalus hornii, A. Gray. 
 Astragalus lotijlorus Hook. 
 Astragalus lentiginosus Dougl. 
 Astragalus menziesii Gray. 
 Astragalus mollissimus Torr. 
 Astragalus mortoni Nutt. 
 Astragalus palousensis Piper. 
 Astragalus spaldingii Gray. 
 Astragalus tridaclylicus A. Gray. 
 Aragallus lamberti (Pursh.) Greene. 
 Aragallus sericeus (Nutt.) Greene. 
 Aragallus spicatus (Hook.) Rydb. 
 Argemone mexicana L. 
 Cannabis saliva L. 
 
 Crolalaria. 
 
 Cystium diphysum (A. Gray) Rydb. 
 
 Datura stramonium L. . 
 
 Diholcos bisulcatus (Hook.) Rydb. 
 
 Diholcos haydenianus (A. Gray) Rydb. 
 
 Fritillaria pudica Spreng. 
 
 Lathyrus polymorphus Nutt. 
 
 (=L. incanus.) 
 Leucocrinum montanum Nutt. 
 Malvastrum coccineum (Pursh.) Gray. 
 Oxybaphrus. 
 Oxytropis lagopus Nutt. 
 
 (= Aragallus lagopus Nutt.) 
 Physostigma venosum. 
 Psoralea cuspidata Pursh. 
 Khamnus lanceolata Pursh. 
 Sophora sericea Nutt. 
 Stipa viridula Triv. 
 Zygadenus elegans Pursh. 
 
 (=Anticlea elegans (Pursh.) Rydb.
 
 DESCRIPTION OF LOCO PLANTS. 
 
 37 
 
 DESCRIPTION OF ARAGALLUS LAMBERTI. 
 
 AragaUus lamberti (PI. I) is a perennial growing from a root 
 which may extend 2 or 3 feet or more into the ground. It is acau- 
 lescent and the leaves rise to a height of a foot or more. The general 
 habit of the plant is of erectness. The leaflets are oblong, lanceolate, 
 or linear, and are covered with a variable amount of silky hairs. 
 In some varieties this pubescence is quite dense. The flower scapes 
 are longer than the leaves and bear spikes which are either densely 
 or sparsely flowered. The flowers are large and variable in color; 
 the more common color of the plants on the plains is white, but they 
 may be distinctly purple. The variations are from white, through a 
 light purple and lilac, to a distinct purple. In some cases the corolla 
 
 FIG. 1. Distribution of Aragallus lumberti in the United States. 
 
 is white and the calyx red. In the mountain varieties there is the 
 same variability in color, but the darker ones are more common, the 
 predominating colors being deep violets and purples. The white 
 varieties are commonly found in woods and near streams. 
 
 The plants are strikingly beautiful, and grow so abundantly that 
 when in blossom on the plains largo areas are as white as a field cov- 
 ered with snow, while in the mountains, although lass abundant, the 
 patches of several acres of bright purple and violet flowers are 
 extremely attractive. The pods of the Aragattus lamberti are rather 
 long, pubescent, and indistinctly two-celled. It grows most abun- 
 dantly on the low hills of the plains, and in the pastures at the base 
 of the mountains up to a height of perhaps 9,000 feet. It prefers a 
 sandy soil. 
 
 AragdUus lamberti has an extremely wide range, as may bo soon 
 from figure 1. It is found from Alaska on (ho. north down through
 
 38 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 the Dakotas and as far east as central Minnesota; in Montana, Wyo- 
 ming, western Nebraska and Kansas, eastern Colorado, Oklahoma, 
 western Texas, New Mexico, and Arizona. In all these localities 
 more or less damage has been reported, but it is in Wyoming, Colo- 
 rado, and Arizona that the most trouble has occurred. It is abun- 
 dant in the eastern foothills in Colorado, and on many of the moun- 
 tain ranges horses are no longer turned out. It is especially abundant 
 in parts of Elbert, Lincoln, and Cheyenne counties in eastern Colo- 
 rado. In Arizona there is a large amount of this plant about the base 
 of the San Francisco Mountains. It grows more abundantly east of 
 the Continental Divide, but is by no means confined to this region. 
 Considerable patches of it are found on the western slope in Colorado. 
 In this region it has so far done very little damage, and most of the 
 stockmen do not know that it occurs in that region at all. 
 
 The plant belongs to the semiarid region. It is not, however, 
 entirely confined to dry soils and sterile regions. In the Black Hills 
 of South Dakota it occurs in the forests and in soil which, during a 
 part of the year at least, is full of moisture. The pubescence is much 
 more marked in the dry regions. Aragallus lamberti is popularly 
 known as "rattleweed" or "white loco." 
 
 The species spicatus (Hook) Rydb., albiftorus Nelson, and sericeus 
 Gray are considered by Prof. C. F. Wheeler, who has determined our 
 plants, as identical with lamberti. 
 
 DESCRIPTION OF ASTRAGALUS MOLLISSIMUS. 
 
 Astragalus mollissimus (PI. II) is a perennial growing from a long 
 root like that of Aragallus lamberti. Unlike the latter, it has distinct 
 stems in the older plants, although the young plants appear acaules- 
 cent. The plant is inclined to be decumbent, although young plants 
 are sometimes quite erect. In this habit it differs markedly from 
 Aragallus lamberti. Most of the plants are comparatively small, 
 living apparently not more than two or three years. Under favor- 
 able circumstances, however, they may grow into large bushy struc- 
 tures, perhaps a foot high and from 1 to 2 feet in diameter. The 
 leaflets are broadly ovate or elliptical, and densely pubescent. This 
 pubescence is very much greater than in Aragallus lamberti. The 
 flower scapes do not ordinarily much exceed in length the leaves, and 
 bear rather dense spikes of deep violet or purple flowers. The 
 flowers are much smaller than those of Aragallus lamberti and less 
 showy. The pods are thicker than those of Aragallus lamberti, 
 smooth, and distinctly two-celled. 
 
 Plate II, figure 1, shows the appearance of the younger plants and 
 the characteristic appearance of the leaves, flowers, and fruit, while 
 figure 2 of that plate shows the general appearance of the older
 
 BUL. 112, BUREAU OF AMMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE I.
 
 BUL. 112, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE II. 
 
 Fig. 1. Flower and fruit. 
 
 Fin. 2. Habit of plant. 
 PURPLE OR WOOLLY LOCO (ASTRAGALUS MOLLISSIMUS'
 
 DISPERSAL OF LOCO PLANTS. 
 
 39 
 
 plants, in which the decumbent character is more pronounced. It 
 does not grow in as great abundance as the rattleweed, although occa- 
 sionally a few acres may be pretty well covered. It grows best on an 
 adobe soil, and where the two species AragaUus lamberti and Astra- 
 galus moUissimus grow near together, Astragalus moUissimus occupies 
 the depressions and AragaUus lamberti is found on the hills. 
 
 Its range (see fig. 2) is not so wide as that of AragaUus lamberti. It 
 occurs in Wyoming, Nebraska, Kansas, Colorado, Oklahoma, Texas, 
 New Mexico, and Arizona. In the eastern part of the plains region 
 of Colorado and in western Kansas and Nebraska Astragalus moUis- 
 simus is very abundant, while AragaUus lamberti is comparatively 
 rare. The same is true of the Panhandle in Texas. In parts of New 
 
 FIG. 2. Distribution of Antragalu* moUissimus in the United States. 
 
 Mexico it grows very luxuriantly. This is particularly true in some 
 portions of the Estancia Valley and in the regions about Santa Rosa. 
 It is found in less abundance in Arizona, and apparently in that Terri- 
 tory does very little harm. The most harmful of the loco plants in 
 Arizona appear to be entirely distinct from the two species under 
 discussion. 
 
 Astragalus mottissimus is popularly known as "purple loco," 
 "woolly loco," or "Texas loco." Sometimes it is spoken of by the 
 ranchmen as "the loco." 
 
 DISPERSAL OF ARAGALLUS LAMBKKTI AND ASTRAGALUS MOLLISSIMU8. 
 
 When AragaUus lamberti ripens, the pods open while still on the 
 flower scapes and the seed is scattered in the immediate neighbor- 
 hood of the plant. The pods of Astragalus moUissimiu are heavier
 
 40 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 and may lie upon the ground, but because of their weight are not 
 moved to any extent by the winds. Neither of these plants breaks 
 off and becomes scattered in tumbleweed fashion. It follows that in 
 the case of both of these species most of the new plants spring up in 
 the immediate neighborhood of the parent plant, and the dispersal of 
 the plants is a comparatively slow matter. It should not be assumed 
 that the wind has no influence in scattering the seeds, for in a countiy 
 of violent wind, seed, like everything else that is loose, will be carried 
 about more or less. This is shown in the fact that Astragalus mollis- 
 simus is frequently abundant in and near wagon roads, doubtless 
 because the moving seeds have been arrested hi the depressions. 
 Loco is said to be especially abundant near old sheep trails. This 
 may be partly because of the seeds carried in the droppings of the 
 sheep and partly because of the arrest of the moving seeds by the 
 depressions and the planting of these seeds by the feet of the sheep. 
 It is said by some (Blankinship, 1903) that the bison were instru- 
 mental in the distribution of the plants either through their drop- 
 pings or because of their habits of wallowing, by reason of which they 
 may have carried the seed to great distances. These statements in 
 regard to the distribution by sheep and bison, however, are entirely 
 theoretical, for no exact observations have been made. 
 
 RELATIONS OF LOCO PLANTS TO FERTILE SOIL. 
 
 Incidentally it may be remarked that the loco weeds, like other 
 leguminous plants, have root tubercles, and presumably are effica- 
 cious in adding nitrogen to the soil content. Mr. W. S. Pershing, of 
 Limon, Colo., states that he has noticed that he has had especially 
 good crops when he has used land on which loco has been growing. 
 It seems very possible that while loco is a curse to the stockmen it 
 may be of some benefit to the farmer. 
 
 EXPERIMENTAL WORK LIMITED TO TWO PLANTS. 
 
 The experimental work on which this paper was based was limited 
 to the two species Astragalus mollissimus and Aragallus lamberti. 
 There is reason to believe, however, that a considerable number of 
 related plants may possess the same properties. 
 
 Horses in Arizona and New Mexico die with the typical symptoms 
 of loco poisoning, and post-mortem examinations show lesions simi- 
 lar to those found in the victims of Astragalus mollissimus or Ara- 
 gallus lamberti, but the loco plants are different species from those 
 found farther north. While there is little reason to doubt that these 
 plants possess the same poisonous principle and produce the same 
 result, experimental work has not been undertaken to demonstrate 
 these facts.
 
 OTHER PLANTS PRODUCING SIMILAR SYMPTOMS. 41 
 
 Through many parts of the West horses are said to become "saged" 
 and to have many of the symptoms of loco poisoning. This has been 
 noted by Mayo. The author has seen some cases of so-called saged 
 horses, but there was no means of proving that they had not been 
 eating loco plants. The testimony of stockmen who have what 
 seems to them clear evidence of the production of these symptoms 
 by the sages is not to be lightly set aside. It is hoped that it may 
 be possible to do some convincing experimental work on these plants. 
 
 Reference should be made, in passing, to the poisonous effects of 
 Swainsona galegifolia, known as the Darling pea or indigo plant, 
 and other species of Swainsona which are said to produce hi Aus- 
 tralia symptoms like those caused by the American loco plants. 
 MacOwan considers the "nenta" of the Cape as produced in a 
 similar way.
 
 PART II. EXPERIMENTAL WORK. 
 
 THE PROBLEM TO BE SOLVED. 
 
 It will be seen from the foregoing that when, at the earnest and 
 persistent solicitation of the stockmen, it was decided by the Depart- 
 ment of Agriculture to make a thorough study of the subject, there 
 was very little definite knowledge to start upon. In spite of the 
 fact that the subject had been under investigation for a third of a 
 century, there was no consensus of opinion even in regard to the 
 poisonous or nonpoisonous character of the plants themselves. The 
 stockmen with very few exceptions were convinced that the plants 
 were the cause of the disease. On the other hand, laboratory in- 
 vestigations were contradictory and the investigations in the field 
 were not conclusive. The problem, as presented to the Department 
 then, involved: 
 
 1. The definite determination of the poisonous or nonpoisonous 
 character of the loco plants. This included (a) field experiments 
 in feeding animals under normal conditions, with proper controls, 
 to find out whether the disease could be produced by the loco plants, 
 and (&) a pharmacological examination of the plants to determine 
 whether a poisonous principle could be extracted, and if it could be 
 extracted to determine its properties. The pharmacological work 
 was entirely in the hands of Dr. Albert C. Crawford, who has made 
 an independent report of his investigations. 
 
 2. A careful examination of locoed animals, with numerous post- 
 mortems to determine the pathological lesions, with the end in view 
 of making an accurate and fairly complete diagnosis of the disease 
 from the pathological side. 
 
 3. An attempt to find some remedy for the trouble. This branch 
 of the subject presented two aspects: (a) The suggestion of measures 
 to eradicate the plant or to reduce its numbers, if it was found to be 
 the cause of the disease; (6) the suggestion of remedies which could 
 be given to the animals either for a cure or for lessening the effects 
 of the disease. 
 
 It was evident that the investigation would have to be equipped 
 in a very broad way. While the study was primarily of the loco 
 
 a Bulletin 129, Bureau of Plant Industry. 
 42
 
 PLAN OF EXPERIMENT. 43 
 
 plants, it was necessary to be provided with means of making post- 
 mortems, giving special attention to the presence of animal parasites; 
 pathological tissues, must also be collected and examined, the blood 
 must be studied, and an equipment for the cultivation of pathogenic 
 bacteria must be on hand. 
 
 PLAN OF WORK. 
 
 To carry out the first point in the investigation, it was determined 
 to secure the use of land somewhere in the loco area, and fence in 
 one piece covered with loco thickly enough so that the animals in 
 the pasture would be compelled to eat loco, but with grass enough 
 so that there would be no question of starvation. Another piece of 
 ground, as nearly like the first as possible, but free from loco, was to 
 be used as a control pasture. In addition, animals should be con- 
 fined in the corrals and fed on cut loco, cut loco and hay, etc. It 
 would be necessary also to confine certain groups of animals to definite 
 loco species, and thus determine the differences, if any, in their 
 poisonous properties. Incidentally, it was desired to travel through 
 the loco country arid collect facts in regard to the losses from loco, 
 the loco conditions in different places, and the distribution of the 
 supposed poisonous plants. 
 
 LOCATION OF EXPERIMENT. 
 
 As Colorado has perhaps suffered more losses from loco than any 
 other region it was determined to locate the experiment in that 
 State. A cooperative agreement was entered into with the Colo- 
 ratio Agricultural Experiment Station .by which the station agreed 
 to furnish, in aid of the work, the stock to be experimented upon 
 and the services of a veterinarian for consultation when called upon. 
 After some time spent by Doctor True and the author in examining 
 different areas of the State where loco was doing most harm, it was 
 decided to locate a temporary station at Hugo, in Lincoln County. 
 The choice of this location was determined, in part, by the fact 
 that no part of the West has suffered more from loco than this section 
 of Colorado, and in part because of the active interest in the inves- 
 tigation manifested by the stockmen of that neighborhood. 
 
 In this connection the author makes grateful acknowledgment of 
 the courtesies extended and valuable assistance rendered by many 
 persons, too numerous to mention l>y name, in the course of the inves- 
 tigations. The stockmen not only gave freely of their time in show- 
 ing local conditions, but were always ready to furnish animals for 
 autopsy and to assist in their examination. The county board of 
 Lincoln County made liberal appropriations for the experiment.
 
 44 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 Special acknowledgment, too, should be made of the assistance very 
 freely given by the railroad officials in the territory visited ; without 
 this help it would have been impossible to handle the work with the 
 funds at our disposal. 
 
 PRELIMINARY WORK. 
 
 During a preliminary trip through the State a considerable number 
 of locoed animals were seen. The picture in the text of case 513 
 (fig. 3) , a stunted colt seen near Wray, is typical of the locoed horses 
 observed on this trip. In spite of many cases, where there was an 
 abundance of feed, the conclusion was reached that in the great ma- 
 jority of cases starvation was the principal if not the only factor in 
 the so-called loco disease. Prof. W. L. Carlyle, of the Agricultural Col- 
 lege, accompanied us 
 in our examination 
 of the neighborhood 
 of Hugo, and agreed 
 with us that an abun- 
 dance of good feed 
 would greatly reduce 
 the number of cases 
 and perhaps elimi- 
 nate the problem. 
 
 An old ranch house 
 with its corrals was 
 secured as laboratory 
 headquarters for the 
 work. A piece of 
 ground of something 
 over 200 acres, where 
 the Aragallus lamberti was especially thick, was prepared as a loco 
 pasture and was so fenced that the animals should always have 
 access to running water. Over the whole of this 200-acre pasture the 
 Aragallus lamberti was distributed in very great abundance. It is 
 doubtful if there was a square yard of the pasture which did not have 
 one or more of the plants. It was also very nearly a field of Ara- 
 gallus lamberti simply. There w r ere in the depressions small patches 
 of Astragalus mollissimus, but during the progress of the experiment 
 the animals were watched carefully, and there is reason to think that 
 none of them ate this plant in this pasture. 
 
 Another piece of ground near by was arranged for a control pas- 
 ture. This piece of land had a comparatively small amount of loco 
 upon it. A force was set at work to clear out this pasture so that it 
 would be to all intents and purposes a loco-free piece of ground. 
 During the summer men were sent over it two or three times in addi- 
 
 FIG. 3. Case 513. A locoed colt, stunted in its growth by loco 
 poisoning.
 
 THE FIRST SEASON'S WORK. 45 
 
 tion, in order to kill out the seedlings as they came up later in the 
 season. Thus in this pasture we had a piece of ground very nearly 
 like the loco pasture but without the loco plants. Inasmuch, how- 
 ever, as the loco-free pasture was somewhat lower, it is a fact that the 
 grass was rather better than in the loco pasture. However, there 
 was an abundance of grass in the loco pasture, so that we consider 
 that the starvation element was entirely eliminated. 
 
 WORK OF THE FIRST SEASON. 
 
 Twelve steers and fifteen horses were received from the agricul- 
 tural experiment station for experimental purposes. Part of these 
 arrived at the end of April, 1905, and part the first week in May. By 
 the end of the first week in May the experiment was fairly started. 
 The animals were given individual brands and numbered, so that the 
 notes of each animal could be kept under its own number. Five of 
 the cattle, Nos. 1, 2, 4, 5, and 6, and four of the horses, Nos. 13, 16, 
 22, and 23, were put in the loco-free pasture and kept there through 
 the season as controls. In selecting these controls the animals were 
 taken by a chance selection in order that the loco animals should be 
 just as good as the controls but no better. The controls had an 
 uneventful history. All kept well and flourished throughout the 
 summer, and came out in the fall in good condition. 
 
 Of the remaining animals part were put in the loco-free pasture to 
 be drawn upon for corral experiments, and part were placed in the 
 loco pasture. In order to induce the loco animals to eat a large 
 amount of the weed, it was found expedient after the last of May to 
 bring them into the corrals at night and keep them in until rather late 
 the next morning. By this treatment they went to the pastures in 
 the morning very hungry; and as hungry animals and this is espe- 
 cially true of cattle are apt to eat the most prominent plants, they 
 would for an hour or two eat loco almost exclusively. After satis- 
 fying their first hunger they would commence to eat grass. It was 
 found that they ate much less loco when kept in the pasture nights 
 as well as days. 
 
 Astragalus mollissimus did not occur in sufficient amount near 
 Hugo so that a pasture could be arranged where stock could bo fed, 
 and wo found it necessary for experiments on this species to cut the 
 loco and food the animals in the corrals. A little later a considerable 
 piece of ground was found on the Van Antwerp ranch, about 10 miles 
 south of Hugo, where the Astragalus niottissiiHus was particularly 
 luxuriant. This piece of ground was loaned for experimental pur- 
 poses by Mr. Laurie, and wais fenced in as a pasture. Two horses and 
 two steers wore placed in it on July 13. The pasture was visited 
 every other day and the animals were watched to see what thoy were
 
 46 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 eating. It was necessary to construct a lane from the pasture to a 
 well so that they could get water, and in this lane there was a con- 
 siderable amount of Aragallus lamberti. The animals ate this plant, 
 but there is no evidence that they ate any of the Astragalus mollissi- 
 mus. It was hoped that as the grass gradually became shorter they 
 would be forced into eating the weed, but to our surprise within two 
 or three weeks nearly all the Astragalus mollissimus was dead, having 
 succumbed to insect enemies. On August 25 it was decided to take 
 the animals out and abandon the pasture, as there was not enough of 
 the loco left to form any prominent part of their food. There was no 
 evidence that the animals in this pasture had eaten any of the loco 
 even when it was most abundant, so the pasture experiment upon 
 Astragalus mollissimus must be considered as a failure. 
 
 All the animals, when received in the spring, with the exception of 
 one horse which died soon after its arrival in Hugo, were in apparently 
 healthy condition, although rough and poor, as they had just come 
 off the range and suffered more or less from short winter feed. As the 
 result of good pasture, all commenced immediately to improve. The 
 steers in the loco pasture ate Aragallus lamberti freely, and while we 
 at first imagined that they were affected by it, it soon became evident 
 that they were thriving. T.heir coats became smooth, they gained in 
 flesh, and seemed to give evidence that the loco diet was an excellent 
 one. The earlier autopsies, too, instead of showing the presence of 
 intestinal parasites, as had been expected, apparently showed that 
 loco animals had fewer internal parasites than would be expected in 
 normal animals. Our skepticism in regard to the poisonous effect of 
 loco was confirmed, and it appeared probable that we should prove 
 that loco was a myth, or, at least, a misconception, and that the cause 
 of the disease must be sought in some other direction. As the season 
 progressed, however, occasion was found for a change of opinion, as 
 will be seen after the description and detailed discussion of the cases. 
 
 The experiment was carried on through the season with no unex- 
 pected difficulties of a serious nature, with the exception of the appear- 
 ance of glanders in the loco pasture. Suddenly one of the best of the 
 horses developed this disease in an acute form and died after a short 
 illness. This case was followed by another, which also died. For- 
 tunately the disposition of the animals just at that time was such 
 that there was reason to think that only one other horse had been 
 exposed. This horse was isolated for a time, care was taken to give 
 the pasture a chance for disinfection, and the experiment was resumed 
 with no further untoward result. It is to be presumed that this case 
 resulted from infection received before the animals arrived in Hugo. 
 
 A brief history is given in the succeeding pages of some of the more 
 interesting cases. In these statements the results of the autopsies 
 are not mentioned, as they are discussed in some detail later (see 
 p. 95).
 
 EXPERIMENTS WITH CATTLE, 1905. 47 
 
 EXPERIMENTS WITH CATTLE. 
 
 Case 7. This steer was pastured on Aragallus lamberti during the 
 first part of the season. Later it was taken into the corral and fed 
 exclusively on cut Aragallus lamberti. This was eaten very freely for 
 a short time, when the animal showed distaste for it, and the experi- 
 ment was tried of feeding Astragalus mollissimus in the corral. This 
 the steer utterly refused to eat even when starved to it. When on 
 occasional days the animal was turned out into the pasture it would 
 eat grass and Aragallus lamberti. In order that it might not starve 
 to death, it was afterwards turned into the Aragallus lamberti pas- 
 ture, remaining in the pasture until October. In the middle of Octo- 
 ber it suddenly began to show weakness when walking, this being espe- 
 cially noticeable in its hind legs, and within two weeks of the time 
 when the first symptoms were noticed it was found down in the pas- 
 ture, and was killed and autopsied. This was a clear case of poison- 
 ing from the eating of Aragallus lamberti. 
 
 Case 8. This steer was pastured on Aragallus lamberti from the 
 first of the season of 1905, and no effects were noticed until the latter 
 part of July, when it developed a solitary habit, and early in August 
 was found to be very weak, stepping high and straddling with 
 what are considered the peculiar loco motions. Plate III, fig- 
 ures 4 and 5, show this peculiarity of walking quite clearly. On 
 August 27 the animal was down and unable to stand. When assisted 
 to get upon its feet it would balance itself and fall over. Figure 6 
 of Plate III shows the animal in the act of attempting to stand 
 after being assisted. At this time it would eat nothing, but would 
 still drink a little water. This weakness came on very suddenly, for 
 on August 26 it was driven to the pasture and came in in fairly good 
 condition. The steer was killed on October 28 and the autopsy 
 made. 
 
 Case 9. This steer was fed on Aragallus lamberti from the begin- 
 ning of the season. A note was made the latter part of May showing 
 that the animal was in especially good condition at that time. At 
 the end of June it was taken into the corral and fed cut Astragalus 
 mottissimus. It ate freely at first but afterwards refused the plant, 
 and an attempt was made to tempt it by mixing grain with the loco. 
 It ate this for a little time, but soon would not eat the loco even with 
 the chop, and because of the fear of starvation it was turned into the 
 Aragallus lamberti pasture on July 21. At first the steer appeared 
 to pick up and presented a very much bettor appearance. On August 
 30 it was taken into the corral again and fed with a mixture of 
 Astragalus mottissiiMU and hay. It would oat the hay, but did not 
 care for the loco. It was kept in the corral until September 1 7, during 
 all this time eating the hay, but refusing the loco. As it was found 
 impossible to make the animal oat the loco, the exjx'riincnt of feeding
 
 48 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 in the corral was abandoned, and it was turned into the loco pasture, 
 where it commenced to eat Aragallus lamberti again. On October 14 
 it was noticed that the steer was very weak and would fall when 
 driven rapidly. On October 27 it seemed best to kill the animal and 
 make an autopsy. 
 
 Case 10. This case was one of particular interest, as shown in the 
 history of this and the succeeding years. The steer was put in the 
 Aragallus lamberti pasture at the beginning of the season and on 
 July 15 was taken to the Van Antwerp pasture with the hope of 
 getting him to eat Astragalus mollissimus. This pasture at that time 
 was filled with purple loco, and there was a considerable amount of 
 Aragallus lamberti in the lane leading from the pasture to the corrals. 
 There is no evidence that the steer ate any of the Astragalus mol- 
 lissimus, but Aragallus lamberti was eaten by some of the animals and 
 doubtless it had its share. Because of the destruction of the As- 
 tragalus mollissimus, on August 25 it was returned to the Aragallus 
 lamberti pasture. The animal ate more or less of the Aragallus 
 lamberti during the season, generally less, and as the season went on 
 it ate less than in the earlier part of the year. On September 19 it 
 was taken into the corrals and fed upon Astragalus mollissimus and 
 hay. This diet was fed until October 8, but the steer continuously 
 refused the Astragalus mollissimus. It was found impossible to 
 force the loco diet and the animal was turned back into the Ara- 
 gallus lamberti pasture on September 24. During the rest of the sea- 
 son it ate very little of the loco and at the end of the season was in 
 good condition. This animal, it will be noticed, apparently ate 
 the loco mainly because it was green and fresh and did not at any 
 time acquire an appetite that would lead it to eat the plant in 
 preference to grass. 
 
 Case 11. This steer was placed in the Aragallus lamberti pasture 
 at the opening of the season and ate loco from the start. No notice- 
 able effect appeared until October. On the 16th of this month it 
 fell when it was being driven into the pasture, and fell again at night 
 as it was being brought in, showing that it had become extremely 
 weak. At this time it was poor but by no means in a starving 
 condition. It grew steadily worse, and on October 26 was found 
 down and unable to rise. Its eyes were staring, its head shaking, 
 and its coat rough. It was killed and an autopsy made October 27. 
 
 Case 12. This was a black steer which was placed in the Aragallus 
 lamberti pasture at the beginning of the season. This and No. 8 ate 
 loco more freely than the other steers, and it was noticed that they 
 were physicked more than was the case with the other animals. 
 During the first part of the season both appeared to thrive upon the 
 Aragallus lamberti. On May 30 this animal was taken into the corral 
 and fed Astragalus mollissimus exclusively. At first it ate freely,
 
 EXPERIMENTS WITH HORSES, 1905. 49 
 
 but later ate very little and finally refused absolutely to touch it and 
 became very poor. On June 7 Aragallus lamberti was placed before 
 the steer and it immediately commenced to eat it. Then the experi- 
 ment was tried of mixing Astragalus mollissimus and AragaUus 
 lamberti, and it was found that the animal would pick out the 
 AragaUus lamberti and eat it but would leave all the Astragalus 
 mollissimus. As it was evident that the animal would not acquire 
 a taste for Astragalus moUissimus it was put on a diet of AragaUus 
 lamberti in the corral. It was fed this exclusively from July 3 until 
 July 24, but during this period was driven into the pasture on Sundays. 
 In the pasture also it was noticed that it ate Aragallus lamberti very 
 freely. The AragaUus lamberti was supplied to it in the corral in 
 abundance and it ate very readily, but became steadily poorer, its 
 coat becoming rough. During the last week of the corral treatment 
 chop was mixed with the loco in order that it might not be without 
 nutritive food, but on July 24 it was so much reduced that there 
 seemed to be danger of starvation. Accordingly it was turned out 
 into the pasture in the hope that it might pick up. Instead of picking 
 up, however, it grew worse and became so weak that on August 1 
 it was found unwise to try to get it into the corrals. It steadily 
 grew poorer and an autopsy was made on August 5. 
 
 EXPERIMENTS WITH HORSES. 
 
 Case 17. This animal was an iron-gray horse, one of the best 
 appearing animals of the lot received in 1905. Full of life and with a 
 good gait, it was remarked by horsemen who examined the animals 
 that he was an exceptionally good-looking animal. He was placed 
 in the Aragallus lamberti pasture at the beginning of the season and 
 presumably ate no loco at that time. On May 20 the horse was taken 
 into the corral and fed upon cut AragaUus lamberti. He did not eat 
 it readily at first, but afterwards ate it fairly well. On May 28 the 
 horse was showing a very decided loss of flesh and his excess of life 
 had disappeared. He had become a sleepy and dull horse. While 
 he was being fed in the corral on June 6 he managed to get hold of a 
 box of Astragalus mollifssimus roots and devoured them very greedily. 
 It was noticed, too, that when a wagon loaded with Astragalus 
 mollissimus was driven into the corral he tried to get the loco from 
 the sacks, although there was at the same time uneaten Aragallus 
 lamberti in the corral. It was found at this time that he would make 
 his way past numerous obstacles to get at bags of roots of As- 
 tragalus moUissimus. Although the way was barred, he would find 
 the sacks and steal them. Our first impression was that he had a 
 real passion for this loco. On June 8 the experiment was tried of 
 mixing Astragalus moU/brimus and Aragallus lamberti, when it was. 
 79154- Bull. 11209 4
 
 50 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 found that he very carefully picked out the mollissimus and left the 
 lamberti. He was then taken out to the pasture where both weeds 
 were growing to see whether he would manifest the same choice, but 
 there he devoted himself to grass, ignoring both kinds of loco. 
 Later on, in thinking over the matter, the conclusion was reached that 
 while he might have had some desire for the Astragalus mollissimus, 
 the stealing of the roots and the cut loco might be explained simply 
 as a desire to steal rather then a preference for the loco itself, because 
 it would seem that if he really was anxious to get the loco he would 
 have picked it out in the field, where there was an abundance of it. 
 
 The horse had become very poor at this time July 18 and as 
 it was deemed unwise to leave him in the corral he was put in the 
 pasture and soon showed marked improvement. Up to this time 
 there was no reason to think that he had eaten Aragallus lamberti 
 in the field, but from now on he ate it quite freely. From August 
 2 to August 25 he was kept in the hospital pasture for fear of infec- 
 tion from glanders. Then he was returned to the Aragallus lamberti 
 pasture and soon developed a solitary habit, grew exceedingly poor, 
 and on September 20 was found in a dying condition. 
 
 Case 18. This animal was kept in the Aragallus lamberti pasture 
 from the beginning of the season until May 6, when it was taken into 
 the corral and fed upon cut Aragallus lamberti. She ate it very freely 
 almost from the start. From May 9 to May 21 she was kept in the 
 pasture, and during this time apparently ate very little Aragallus 
 lamberti. On the latter date she was again taken to the corral and fed 
 with the cut weed. A week later, as she showed distinct evidence of 
 having become poorer, and had a very sleepy appearance, she was 
 put in the loco field for two or three days, where she ate Aragallus 
 lamberti very freely. Then she was again taken into the corral and 
 fed exclusively on Aragallus lamberti, except as she was allowed the 
 run of the pasture on Sundays. She showed continuous loss of flesh 
 until July 1, when she died very suddenly. During this time she had 
 shown no peculiar nervous symptoms, but had simply gradually 
 wasted away. The result of the experiment seemed to indicate that 
 there was a lack of nutritive material in the plant, and that death was 
 not only the result of poisoning, but probably the result of starvation. 
 Plate IV, figures 1 and 2, show the condition of the animal after it 
 had become locoed. 
 
 Case 19. ^ This mare was kept in the loco-free pasture until August 
 18. At that time she was taken into the corral and fed on Astragalus 
 mollissimus and hay. She ate very freely in the corral, ordinarily 
 picking out the loco from the hay, but also eating fairly well of hay. 
 Later in the experiment there was a period when she picked out the 
 hay rather than the loco, but most of the time she seemed to prefer
 
 But. 112, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE 
 
 CaseS, July 19, 1905. Just before the locoed con- 
 dition was particularly evident. 
 
 CaseS, Augusts, 1905. When the animal showed 
 typical symptoms of loco poisoning, especially 
 in its attitude. 
 
 CaseS, August 23, 1905. Emaciated condition of 
 animal and typical loco attitude of lowered head 
 and braced legs. 
 
 Case 8, August 23, 1905. Loco leaping unneces- 
 sarily high in going over a rut in the road. 
 
 CaseS, August 23, 1905. Loco lifting foot unnec- 
 essarily high in passing over a wire. 
 
 Case ti, August 27, l'A>5. Animal too weak to stand 
 unaided.
 
 BUL. 112, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE IV. 
 
 Case 18, May 12, 1905. A mare weakened by k 
 poisoning. 
 
 Case 18, June 27, 1905. Advanced condition of 
 loco poisoning. 
 
 Case 19, May 16, 1905. Horse before eating any 
 of the loco weed. 
 
 Case 19, August 31, 1905. Animal eating loco at 
 a time when it had lost some flesh, but was nut 
 in bad condition. 
 
 Case IV, Ot"bor 15, 1905. Animal in a very much 
 reduced and emaciated condition. 
 
 Case 19, October 26, 1905. Animal just before its 
 death.
 
 BUL. 112, BUREAU OF AMMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE V. 
 
 Case 524. Peculiar way in which a locoed horse 
 uses its mouth in attempting to eat. 
 
 Case 533. How a locoed horse will rear when 
 suddenly startled. 
 
 Case 525. Peculiar gait which a locoed horse 
 exhibits. 
 
 Case 525. Locoed horse rearing when suddenly 
 startled by a hat thrown out in front of it. 
 
 Case 52V. A loroed An^-nr.* goat unable to 
 upon its fei-t. but otherwise fairly well. 
 
 Another attitude of Case 52V.
 
 EXPERIMENTS WITH HORSES, 1905. 51 
 
 the loco. The experiment was continued until October 15, with the 
 exception of Sundays, when she was allowed to run in the pasture. 
 During this time she lost flesh very decidedly. From October 15 to 
 October 18 she was kept in the Aragattus lamberti pasture to see if the 
 freedom of the pasture would not cause her to pick up somewhat in 
 strength and in flesh. She was brought into the corral on the morn- 
 ing of October 18 very poor and lifeless, dragging her hind feet as 
 she walked, the near foot being more affected apparently than the 
 off foot. It was decided to give her hay with chop for a few days to 
 see if she could not be brought out of the diseased condition. She 
 refused to eat the chop and on October 21 would eat neither chop. nor 
 oats, but would eat hay. She remained in the corrals until October 
 26, when she died and the autopsy was made. The death in this case 
 was at least partly caused by starvation as well as by the effect of the 
 poison. Plate IV, figures 3 to 6, show the change in the condition of 
 the animal. 
 
 Case 20. This was a yearling mare which was placed in the Ara- 
 gaUus lamberti pasture on May 8. She was not observed to be eating 
 any loco until the latter part of August. After that time she ate more 
 or less Aragallus lamberti. We do not know that the mare ate any 
 large amount at any time, but she grew poorer steadily and disap- 
 peared on September 21, and was found dead a day or two later. 
 The animal was interesting in that the poison took effect in a compara- 
 tively short time and rather unexpectedly. 
 
 Case 24. No. 24 was a 6-year-old horse, a good-looking animal. 
 He moved with erect head and long step, and was marked as one of 
 the better appearing horses in the experiment. He remained in the 
 loco-free pasture until the end of May and then was fed in the corral 
 upon cut Astragalus mollissimus. He ate it very freely, in fact would 
 eat about all that was furnished. This diet was continued until 
 June 11, when the horse was turned out for a day. When returned to 
 the corral he took the loco again very readily, although he did not 
 seem hungry. There was no evidence that the horse ate any loco at 
 all while in the field. At first there seemed to bo no effect from this 
 feeding experiment. The animal did not lose flesh, retained its 
 spirits, and showed no symptoms of unhealthy nervousness. After 
 the middle of June, however, he gradually lost flesh and early in July 
 he was so poor that it seemed likely that wo might have a case of 
 starvation, so he was turned into the pasture to pick up. The animal 
 still seemed to have fairly good spirits, carrying its head high, but the 
 coat was rough and the bones exceedingly prominent. In the pasture 
 he ate the grass, not caring for the loco, and it was ho|>ed he would 
 gradually pick up and got in form for further experimentation. Some- 
 what to our surprise on July 8 the horse was found dead. He lay
 
 52 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 under a barbed wire fence and it was evident had kicked about for a 
 considerable time before death. His death could not have been 
 entirely the result of weakness. 
 
 It may be mentioned as a feature of this case that during the latter 
 part of the horse's stay in the corral tumors as large as a small fist, 
 one or two at a time, would appear upon the groin. These appeared 
 and disappeared in a day or two. None were noticeable at the time 
 of death. 
 
 Case 26. This horse was taken from the loco-free pasture on July 
 13 to the Van Antwerp pasture to experiment with Astragalus mol- 
 lissimus. There is no evidence that the animal ate any of the 
 Astragalus mollissimus in this pasture, nor does it seem probable that 
 it ate the AragaUus lamberti. 
 
 Because of the death of the purple loco the horse was brought back 
 and placed in the AragaUus lamberti pasture on August 25. It began 
 to eat the loco within two weeks, and soon it and its companion horse 
 developed the solitary habit. The horse ate the weed continuously 
 until September 15, when it died somewhat suddenly. The animal 
 before this had shown a peculiar straddling gait which was especially 
 noticeable in its hind legs, but it did not seem to be particularly weak 
 nor in a bad condition. 
 
 CASES OF CATTLE AND HORSES NOT SUBJECTS OF EXPERIMENT. 
 
 Besides work upon the station animals a considerable number of 
 locoed cattle and horses were examined at ranches near Hugo and 
 at other points in Colorado. In most cases autopsies were made. 
 Some of the more interesting cases will be briefly mentioned below. 
 
 Case 501 . This was a cow belonging to Mr. Frank Ewing, of Hugo. 
 When found the animal was too badly decayed for autopsy, but it 
 was a particularly interesting case of the very pronounced swelling 
 under the jaw, which is considered as one of the peculiar symptoms 
 of loco poisoning. The tumor was filled with a clear serous fluid. 
 
 Case 503. This was a 2-year-old steer belonging to Mr. William 
 Hazel, of Hugo. This case is interesting as being a typical locoed 
 range steer. The animal was found near a watering place about 2 
 miles from the loco station. It was down, but with head erect. Its 
 eyes were sunken and staring, its coat rough and very poor. When 
 startled it responded with peculiar nervous twitchings. 
 
 Case 519. This was the first horse upon which an autopsy was 
 made. It belonged to Mr. Charles Johnson, of Akron, Colo., and had 
 been considered one of his best horses. The animal had been eating 
 loco for two or three years. It was poor in flesh, with shaggy mane 
 and tail, its coat was rough, the hair being off in patches, and it 
 walked with a peculiar stiff, irregular motion of the legs, and had 
 become absolutely worthless.
 
 MISCELLANEOUS CASES, 1905. 53 
 
 Case 524- This was a colt belonging to Mr. Kendrick, of Seibert, 
 Colo. The interest connected with this animal was largely in its 
 peculiar way of eating. It had been taken into the corral to feed in 
 order to get rid of the loco symptoms. It was in good flesh, but 
 very nervous, constantly walking about the corral. Plate V, figure 
 1, shows the peculiar nibbling way of eating, a motion that is char- 
 acteristic of locoed animals. 
 
 Case 525. This was a horse belonging to Mr. John Lieber, of 
 Hugo, and is referred to in this place because of the particularly 
 good pictures (PI. V, figs. 3 and 4) which were obtained of its atti- 
 tudes, which show the peculiar gait of a locoed animal and the 
 attitude which one is likely to assume when startled. The horse was 
 very poor, being little but skin and bones, with rough coat and shaggy 
 mane and tail. When walking over a railroad track it was noticed 
 that its feet were lifted very high in order to clear the rails. 
 
 Case 533. In this case, too, a particularly good picture (PI. V, 
 fig. 2) was obtained of the position assumed when startled. This 
 horse was seen on a ranch north of Claremont, Colo. 
 
 ( 'ax? 529. This case was one of considerable interest, as being the 
 only case of a locoed goat encountered during the season's work. 
 The animal was an Angora goat belonging to Mr. Lon Foote, of Hugo. 
 It was received at the experiment station on September 23, 1905, 
 and at that time was unable to stand. The animal moved its legs 
 spasmodically, and by great effort, with assistance, would get upon 
 its feet, but would soon fall down, falling clear over, with its head 
 prone upon the ground. It would eat grain very freely and would 
 drink readily. The first impression on seeing it as it lay upon the 
 ground was that it was in the agonies of death, because of the peculiar 
 convulsive movements of its legs. The owner said that it had been 
 in the corral since spring. During the winter it had eaten very 
 freely of Aragallns lamberti, and its present condition was considered 
 as entirely due to this food. The goat was kept at the loco station 
 from September 23 to September 29, and during that time showed 
 very little change in condition, except that it grew somewhat weaker. 
 Within two or three days after arrival at the ranch the goat was 
 unable to stand upon its feet at all, and could not even sit with the 
 head in an erect position for any length of time. When put in a 
 sitting position so that it could eat, the goat would do so for a little 
 time, then with a peculiar jerky, convulsive movement the head 
 would be thrown back bit by bit, finally falling over on the side, with 
 the horns lying flat on the ground. As it seemed probable that noth- 
 ing more could be gained by keeping it, the goat was killed and au- 
 topsied. Plate V, figures /> and 0, show the characteristic attitude* 
 assumed l>\ the animal.
 
 54 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 SUMMARY OF FIRST SEASON'S WORK. 
 
 The detailed discussion of the results of the work of 1905 will be 
 taken up after the description of the cases of the second year. It 
 may be well, however, to insert here the statement which was formu- 
 lated at the end of the season as embodying the results so far obtained. 
 
 1. There is no longer any question of the poisonous effect of the 
 loco weeds. The results of the feeding experiment at the ranch seem 
 to prove conclusively that Aragallus lamberti, or rattleweed, when 
 eaten for a prolonged period of time, has an effect of poisoning upon 
 the nervous system, which leads to a lack of muscular coordination. 
 The animal's nervous system becomes impaired to such an extent 
 that the nutritive functions. are interfered with and the victim per- 
 ishes by starvation. The presence of ulcers in the fourth stomach 
 of some of the steers may possibly be a characteristic lesion. The 
 finding of a serous exudate in the spinal canal in certain of the 
 autopsies would seem to indicate that this is another definite lesion 
 produced by loco. 
 
 2. Aragallus lamberti will evidently poison both horses and cattle; 
 presumably also it has the same effect upon sheep, although the 
 season's experiments did not have enough to do with sheep to make 
 this at all evident. 
 
 3. Astragalus mollissimus has the same general effect upon horses 
 and sheep as Aragallus lamberti. They do not eat it as readily, but 
 when eaten it has the same general effect. 
 
 4. Cattle can be poisoned by Astragalus mollissimus, though as a 
 matter of fact they rarely eat it. It was shown quite clearly by the 
 feeding experiments that it was very difficult to make cattle eat this 
 weed. In the neighborhood of Hugo, Colo., loco poisoning may be 
 considered as almost entirely due to Aragallus lamberti. It is 
 noticed, too, that in parts of the State where Astragalus mollissimus 
 is the common loco plant, like the region around Holyoke, locoed 
 cattle are almost entirely unheard of. The same may be said of the 
 Panhandle in Texas, where the common loco plant is Astragalus 
 mollissimus and where locoed cattle are very unusual. It seems prob- 
 able, then, that the generalization may be made that, while both 
 these plants will produce poisonous effects upon both cattle and 
 horses, it is very rare that cattle will eat Astragalus mollissimus, and 
 that so far as the cattle industry is concerned the loss from this 
 plant is probably exceedingly small. 
 
 In the case of horses it appears that while they eat Astragalus 
 mollissimus more readily than do cattle, they are not likely to eat 
 it unless forced by shortness of food, while both horses and cattle 
 may contract the habit of eating Aragallus lamberti even when an 
 abundance of food is present.
 
 SUMMARY OF FIRST SEASON'S WORK. 55 
 
 5. It has been argued by some that the so-called loco disease was 
 simply the result of starvation, and that if animals had sufficient to 
 eat there would be no trouble from loco. The feeding experiments 
 seem to indicate, however, a specific poisonous effect of the weeds. 
 The animals that were fed upon loco alone starved to death, but animals 
 were also given abundance of other feed mixed with loco, and in 
 these cases they also died, showing conclusively that loco kills not 
 simply by a lack of nutrition, but because of a definite poisonous 
 effect produced by the plant itself. 
 
 At the end of the season, about the middle of November, the sur- 
 viving animals were taken to a ranch for the winter, where they were 
 pastured and fed hay when necessary, but none of them had any 
 loco. It was intended that they should have the same care that 
 would -ordinarily be given by the stockmen to animals that were kept 
 under common range conditions. 
 
 WORK OF THE SECOND AND THIRD SEASONS. 
 
 The work of the first season, as has been indicated above, seemed 
 to bring certain fairly definite results. The experiment, however, 
 was on too small a scale, the number of animals was too small, and 
 the general character of the experiment too circumscribed to permit 
 one to speak at all dogmatically as to the deductions which should be 
 made. The autopsies in many cases were performed too hastily for 
 satisfactory results. The labor of conducting the routine work was 
 greater than had been expected and taxed the capacity of the station 
 force seriously. It was therefore necessary to . repeat the work of 
 the first season on a larger scale if possible, and thus confirm or 
 modify the tentative conclusions which had been reached. The plan 
 of the second season (1906) then was on the same general lines as 
 that of the first season, but modified somewhat by the experience 
 already undergone. For example, there seemed no longer any doubt 
 of the poisonous nature of the loco weeds, so that it seemed unneces- 
 sary to carry any large number of control animals. The season's 
 work as planned involved: 
 
 1. Pasture feeding on Aragallus lamberti as in the preceding season. 
 
 2. Corral feeding on both Astragalus inollwsimus and Aragallus 
 lamberti under various conditions. 
 
 .3. Careful post-mortem examinations to determine the definite 
 lesions characteristic of the disease, the work of the first season not 
 being conclusive on this point. 
 
 4. The determinations of ttie effects of loco on sheep as well as on 
 horses and cattle. 
 
 5. Experimentation with such remedial measure's as were indicated 
 by the conclusions already reached.
 
 56 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 6. The extension of the knowledge of loco plants as much as 
 possible. 
 
 The preceding work and the main work of the second year were 
 w r ith Astragalus mottissimus and Aragallus lamberti in a restricted 
 area. Not only should more be known of the extent of the damage 
 from these two species, but it was desirable to know to what extent, 
 if any, other related plants are the cause of similar results. At the 
 conclusion of the second season it appeared that the first four heads 
 had been covered fairly well, while a fair beginning had been made 
 with the last two, although the work was incomplete. 
 
 In addition to the work at Hugo, in which the Colorado Agricul- 
 tural Experiment Station cooperated as in the preceding season, the 
 Department carried on a station at Woodland Park, Colo. Woodland 
 Park is near Pike's Peak, and the conditions are very different from 
 those in the plains, although the most abundant loco plant in this 
 region is considered by botanists to be specifically identical with the 
 Aragallus lamberti of the plains. Another loco plant, Astragalus 
 nitidus, is abundant in the pastures in this neighborhood. 
 
 In cooperation with the Nebraska experiment station, a feeding 
 experiment w r ith Astragalus mollissimus w r as also carried on at 
 Imperial, in western Nebraska. In this region the only abundant 
 species of loco is Astragalus mollissimus. 
 
 The feeding experiment during the second season was carried on 
 in the same general way as during the preceding year. Of the cattle, 
 Nos. 1, 30, 31, 43, 46, and 47, and of the horses Nos. 49, 51, 54, 55, 
 61, and 65 were placed in 'the loco-free pasture as controls and kept 
 there throughout the entire season. All prospered and were in good 
 condition at the end of the season. Of the others, some were pastured 
 in the Aragallus lamberti pasture and some were fed Aragallus lam- 
 berti and hay in the corrals. Twenty-three head of cattle were sub- 
 jected to the feeding experiments, and of these eight were dead at the 
 end of the season and two were locoed, but recovered under treat- 
 ment. The history of some of the more interesting cases follows. 
 In these cases, as in those of 1905, the results of the autopsies are dis- 
 cussed later on in this paper. 
 
 EXPERIMENTS WITH CATTLE. 
 
 Case 2. This was a steer which had been kept in the loco-free 
 pasture during the entire season of 1905 and during the season of 
 1906 until May 9. It was one of the best appearing animals, a par- 
 ticularly good looking and high spirited steer. On the latter date it 
 was placed in the corral and fed on a mixture of hay and fresh cut 
 Aragallus lamberti. At first it refused to eat the loco plant, and when 
 the latter was mixed with the hay would shake out the loco weed and
 
 EXPERIMENTS WITH CATTLE, 1906. 57 
 
 eat the hay, but after a few clays in the corral it ate the loco with a 
 fair degree of readiness. The steer was kept in the corral until August 
 19, except for an occasional day, when it was permitted to run out in 
 the Aragallus lamberti pasture. On May 27, when it was run out in the 
 pasture it was noticed that it would eat nothing but Aragallus lam- 
 berti, and for some time before this date in the corral it had eaten 
 loco rather than hay. 
 
 The first positive symptoms from the eating of Aragallus lamberti 
 were noted on July 19, when it fell as it was passing through a gate to 
 go to water. From this time on it always showed more or less symp- 
 toms of being gate shy; that is, would stoop in passing through a gate 
 as though endeavoring to get under a wire. It became hard to drive 
 and was more and more stupid as time went on. This stupidity was 
 especially marked because of the prior activity of the animal. When 
 kept in the loco-free pasture it had been the source of a good deal of 
 trouble, because it was inclined to break through the fences and, 
 when through, was caught only with difficult}'. During the first 
 week in August the animal lost its appetite and showed great nervous- 
 ness, its head shaking as though it had the palsy. Sometimes in pass- 
 ing through a gate it not only would crouch but would fall down. 
 Plate VII, figure 1, shows the peculiar attitude which it assumed at 
 such times. It became very much constipated, and on August 12, 
 when driven out of the pasture, would continually stumble and fall. 
 It suddenly grew worse, and on August 23 fell and w T as unable to get 
 up again. It died on the 26th and w r as autopsied. 
 
 Case 3. This was another steer remaining from the season of 1905. 
 It was in the loco pasture during that season, but did not show any 
 marked results of poisoning. In the season of 1906 it was placed in 
 the Aragallus lamberti pasture in the spring and immediately com- 
 menced to eat the weed. It ate very freely and began early to show 
 the effect of the poison. On July 3 it was noticed standing by itself 
 in the pasture, and on July 9 its condition was so marked that it 
 seemed desirable to take it to the corral and attempt remedial meas- 
 ures. The steer was accordingly fed hay and chop, part of the hay 
 being alfalfa. It gradually grew worse, however, and on July 16 
 was found down; in the afternoon it was deemed best to kill it and 
 make an autopsy. Plate VI, figure 1 , shows the animal just before its 
 death, and Plate VI, figure 2, shows the interior of the wall of the 
 fourth stomach, with the ulcers which were present in considerable 
 numbers. 
 
 Case 10. This was also an animal which had been experimented 
 upon during the preceding season and had shown only the general 
 effect of what may be called moderate eating. It was placed in the 
 ArayaUu* lamberti pasture in the beginning of the spring of 1906 and 
 ate the weed with considerable freedom. It was noticed toward the
 
 58 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 end of April that the animal was very thin, its coat rough, and that 
 it walked with its head down in a spiritless way. This probably was 
 due not so much to the loco feeding as to the short feeding during the 
 winter, as it had been in the loco pasture only a short time. From 
 this time it commenced to eat AragaUus lamberti, but not very freely. 
 It then weighed 507 pounds; on May 7 its weight was 590 pounds, and 
 its maximum weight during the summer was reached on September 
 7, when it weighed 840 pounds. 
 
 The history of this animal was interesting because, while during 
 the two seasons it ate more or less of the loco, it never ate it in any 
 very large amount. It could well be compared to the moderate 
 drinker of alcoholic liquors, for it was not poisoned so as to show the 
 effect of the weed in a very marked degree, but it was affected to the 
 extent of not gaining as much as would naturally be expected. The 
 curve of the weight (see fig. 4) shows this effect, for if this curve is 
 
 1 
 
 1906 APRti 
 
 M 
 
 4Y 
 
 
 A/E 
 
 JULY 
 
 /H/GUSr 
 
 5^/Vif 
 
 //^W 
 
 OCWSEff 
 
 /W9AT 
 
 1906 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 750 
 
 
 
 
 
 
 
 
 
 
 2C 
 
 
 
 s 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 - J5!5 *- 
 
 ^- 
 
 
 700 
 
 
 
 
 
 
 
 ^ 
 
 z^ 
 
 
 
 
 
 
 
 
 
 650 
 600 
 
 
 
 
 ^ 
 
 ^*- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 FIG. 4. Curve of weight of steer No. 10, 1906. 
 
 compared with those of animals in good pasture it will be noticed 
 that it is flatter, while the animals in good pasture gained with great 
 rapidity until the end of the season. This was the only steer that 
 refused to eat AragaUus lamberti in any large amount. 
 
 During the season of 1907 No. 10 was herded with the other experi- 
 ment animals in the loco pasture and continued as in the preceding 
 seasons to eat more or less of the AragaUus lamberti. At no time, how- 
 ever, did the steer eat enough to show marked effects from the poison. 
 At the end of the season the gain in weight was once more much less 
 than it should have been normally (see fig. 5), but this failure to 
 increase in weight was the only evident effect of the loco poison. 
 Case 10 is a good example of the possibilities of cattle eating loco 
 season after season without showing serious effects from the poison. 
 
 Case 32. This was an Aberdeen Angus cow carrying a registry 
 tag. She was placed in the AragaUus lamberti pasture in April, 
 1906, and commenced immediately to eat the plant. She dropped 
 a calf on May 6. She continued to eat AragaUus lamberti, and her
 
 Buu. 112. BUREAU OF AMMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE VI. 
 
 FIG. 1. CASE 3. EFFECT OF LOCO POISONING, SHOWN IN EMACIATION AND 
 DEJECTED ATTITUDE, JUST BEFORE DEATH OF ANIMAL. 
 
 FIG. 2.-INNEK WALL OF FOURTH STOMACH OF CASE 3. SHOWING ULCERS 
 UPON ITS SURFACE.
 
 BUL. 112, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE VII. 
 
 Case 2, July 25,1906. Steer bending low to avoid Case 34. Another case similar to that in Fig. 1. 
 
 an imaginary obstruction above it while passing 
 through a gate. 
 
 . 
 
 Case67, May 1,1906. A bright heifer calf shortly Case 67, July 5, 1906. Calf shown in Fig. 3. 
 after birth. Effects of loco which it had eaten in imitation 
 
 of its mother. 
 
 Case 67, October 16. 1906. Calf with typical symp- Case 67, October 19, 1906. Animal just before 
 toms of loco. The long hair of the face is death. 
 
 especially noticeable.
 
 EXPERIMENTS WITH CATTLE, 1906. 
 
 59 
 
 weight on July 5 was only 850 pounds as compared with 1,025 pounds 
 on May 3. Of course her weight would have been reduced, in any 
 caser, at the time of the birth of the calf, but, under normal condi- 
 tions, being a large, strong animal, the weight should have been 
 regained in a short time. 
 
 The effect of loco upon her coat was noticed on July 19, although 
 the symptoms were not at that time very pronounced. They became 
 
 1 
 
 1907, 
 
 1W/L 
 
 M, 
 
 W 
 
 JU 
 
 V 
 
 JU t 
 
 >.Y 
 
 /te/6* 
 
 vsr 
 
 Sf/TfMSf/f 
 
 ocro 
 
 fff/f 
 
 MOV 
 
 907 
 
 850 
 600 
 
 
 
 
 
 
 f S 
 
 jg* 
 
 ^s=* 
 
 ,^ 
 
 J^- 
 
 
 
 ~** 
 ^^ 
 
 =*= 
 
 i 
 
 
 
 750 
 
 . ^ 
 
 ~> 
 
 f " 
 
 -/ S 
 
 f~^ 
 
 
 
 
 
 
 
 
 
 
 
 
 Fio. 5. Curve of weight of steer No. 10, 1907. 
 
 more and more so, however, and on July 30 she had great difficulty 
 in getting up after being down, and walked in the typical loco 
 fashion. She died on August 26. The case was one of especial 
 interest because she commenced to eat the loco almost immediately 
 when out in the pasture, and the effects came in a comparatively 
 short time. The effect of the poisoning on her weight is shown in 
 figure 6. 
 
 j 
 
 1000 
 950 
 900 
 850 
 
 1906 JPR/L 
 
 MJV 
 
 JVMf 
 
 jut* 
 
 /WGusr 
 
 strr. 1906 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 ^v 
 
 
 
 
 
 
 
 
 
 
 
 
 X, 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 V 
 
 
 
 
 
 
 
 
 
 
 
 
 ^_ 
 
 
 
 
 
 
 
 
 
 
 
 
 "^ 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 KT 
 
 
 
 
 
 
 
 
 
 
 
 
 x. 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 >y 
 
 
 
 
 
 
 
 i 
 
 
 
 
 
 
 ^. 
 
 
 
 
 
 
 
 
 
 
 
 
 x 
 
 
 
 
 
 
 
 
 
 
 
 
 ^^ 
 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 55 
 
 
 
 
 
 
 
 
 
 
 ITfVG 
 
 *#*6* 
 
 tttt/S-tAMA 
 
 tfftrt 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 KlO. 8. Curve of weight of cow No. 'Si. 
 
 Case 34- This was a cow which commenced to oat loco immediately 
 after being placed in the AragdHus bunbtrti pasture in the spring. 
 She gave birth to a calf on May 3. The calf was weak and unable to 
 stain I and lived only a few days. There was really no reason, how- 
 ever, for supposing that the weak condition of the calf was due to 
 Arayattus lamberti. She ate AragaUus lamberti with great freedom, 
 and earlv in June it was noticed that at times she would go from
 
 60 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 one plant to another, eating nothing at all except the loco weed. 
 Symptoms of loco poison were shown in a marked degree a little 
 before the middle of July. Plate VII, figure 2, shows the condition 
 of the animal at this time, the picture being taken on July 9. It 
 also shows the peculiar crouching attitude which the animal assumed 
 in going through a gate bending down as though she were attempt- 
 ing to get under a wire. On July 19 she was very poor, had a rough 
 coat, straddled as she walked, and showed marked lack of muscu- 
 lar coordination; she was also very weak. She was kept on Ara- 
 gallus lamberti until August 8. The cow was nervous, had lost con- 
 trol of her muscles to a very marked degree, and showed great 
 difficulty in crossing over even the slightest obstructions. On Aug- 
 ust 8 she was kept in and fed alfalfa and hay, and attempts were 
 
 FIG. 7. Curve of weight of cow No. 37. 
 
 made to give her certain medicinal remedies. She grew worse until 
 August 16, when she died and was autopsied. 
 
 Case 37. This was a Hereford cow with a registry tag. She was 
 placed in the Aragallus lainberti pasture in the spring and imme- 
 diately commenced to eat the loco weed. At this time she weighed 
 830 pounds. She gave birth to a calf April 28. She began to show the 
 effect of the loco poison about the middle of July, and the symptoms 
 increased gradually until August 31, when she would fall down when 
 walking. On September 10 she was kept in the corral, as she was at 
 this time very weak, and was fed hay. She weighed then 690 
 pounds. On September 11 she was down and remained down until 
 September 14. During this time she would eat very little. On 
 September 14 she was barely alive, and was killed in the afternoon 
 and autopsied. The curve, figure 7, shows the decline in weight 
 resulting from loco poisoning. 
 
 Case 45- This was a cow which was placed in the loco-free pas- 
 ture in the spring of 1906, weighing at this time 775 pounds. The 
 latter part of May she was taken into the corral to feed fresh cut 
 Aragallus lamberti in order to determine whether loco weed might 
 not produce abortion. She was apparently about three months
 
 EXPERIMENTS WITH CATTLE, 1906. 
 
 61 
 
 along with calf. For the first two or three days the hay was omitted 
 from her feed in order to get her to eat the AragaUus lamberti more 
 freely. After that time, however, she was furnished with an abun- 
 dance of hay so that there might be no question of starvation.- She 
 ate the weed from the start, although not very freely at first, but 
 soon acquired the habit, and when turned out into the pasture it 
 was noticed that she would go from one AragaUus lamberti plant to 
 another, seeming to hunt for the loco, desiring it very much more 
 than grass. On July 21 she was somewhat gate shy, and a few 
 days later her motions in going through a gate very closely resembled 
 those of steer 2. Her calf was dropped on August 5, and it was evi- 
 dent that it was a premature birth. The calf weighed only 14 
 pounds, was about 24 inches long, the hair was not formed, and it 
 may be assumed that it was not more than six months along. 
 
 It would seem probable in this case that AragaUus lamberti had 
 induced the premature birth. She continued to eat the AragaUus 
 lamberti and gradually grew weaker little by little, losing her appetite 
 and not caring to eat much of anything. On August 18 she was 
 
 1 
 
 \90b A 
 
 WIL 
 
 AMY 
 
 JU 
 
 N 
 
 JM 
 
 /!</(> 
 
 
 J-- - - , 
 
 0'.-'' :.' 
 
 NOV. 
 
 woe 
 
 ISO 
 
 
 
 
 
 
 
 ^^ 
 
 ~^~< 
 
 s^. 
 
 s^-- 
 
 
 t 3 - . 
 
 i^' " ' 
 
 
 
 
 \00 
 
 
 
 ~*ao 
 
 RN 
 
 
 
 
 
 
 
 
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 tt 
 
 tff 
 
 
 Fio. 8. Curve of weight of calf No. 00. 
 
 down and could not get up. She was fed and furnished water, but 
 did not get up again, and died on August 31. 
 
 Case 66. This was a male calf dropped by cow 32 on May 6. 
 Its weight on July 5 was 138 pounds. By the middle of July it was 
 eating a good deal of AragaUus lamberti, and continued to eat it 
 very freely; the effects of the poison were evident by the 1st of 
 August. At that time the calf was decidedly constipated and 
 began to be somewhat dull. On August 9 it was very weak and 
 would not follow the others going to the pasture, but laid down and 
 remained away from the rest of the herd. On Scpteml>or 7 its 
 weight was 190 pounds. On October 9 the weight had become 
 reduced to 170 pounds. On October 17 the animal was taken into 
 the corral for dosing. It was pretty far gone, however, anil in a 
 blixzard on October 21 the exposure caused its death. 
 
 This case was particularly interesting, as the calf was born of a 
 cow that was eating loco, and presumably learned to eat from its 
 mother. Although a bright, healthy, and strong calf at the outset 
 it made very little gain in weight and gradually succumbed. The 
 curve, figure 8, shows the changes in weight.
 
 62 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 Case 67. This was a Hereford calf dropped by cow 37 on April 28. 
 It was kept with its mother in the Aragallus lamberti pasture, and by 
 the middle of June was eating pretty freely of the weed. On July 5 
 its weight was 160 pounds. Marked effects from the loco eating 
 appeared about the 1st of August, when it became constipated and 
 dull, and in other ways showed symptoms of the poison. The weight, 
 however, increased until September 7, when it weighed 210 pounds. 
 On September 19 it was put in good pasture, with the intention of 
 
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 1906 / 
 
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 FIG. 9. Curve of weight of calf No. 67. 
 
 making some attempt to cure its locoed condition. From this time 
 on it was kept away from the loco and was dosed. It continually, 
 lost weight, however, and on October 9 weighed only 182^ pounds. 
 Its decline was gradual, and it showed all the symptoms of typical 
 loco. It became very poor, with rough coat, dull eyes, and in walk- 
 ing its head was down in an attitude of peculiar dejection. Plate 
 VII, figure 3, shows the animal soon after birth, when it was a bright 
 and handsome calf. Figure 5, taken October 16, shows the animal 
 
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 1306 x 
 
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 M* 
 
 1Y 
 
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 FIG. 10. Curve of weight of calf No. 68. 
 
 when it had all the typical symptoms of loco poisoning. On October 
 18 it was down in the pasture, and remained down in the same position 
 until its death on October 20. During this time an attempt was 
 made to feed and water it, but without success. Figure 6 shows the 
 attitude assumed by the animal during the last stages. 
 
 This was also a particularly interesting case, as the calf was born 
 of a mother that was eating loco, learned the habit from its mother, 
 and gradually succumbed to the disease.
 
 EXPERIMENTS WITH HORSES, 1906. 
 
 63 
 
 It is of interest to compare this calf with another, No. 68, that was 
 born about a month later. No. 68 was kept in the loco-free pasture 
 through the whole summer. It soon outstripped No. 67 in weight, 
 and at the end of the summer was a strong, healthy calf, weighing 
 350 pounds. The curves of weight of Nos. 67 and 68 are given in 
 figures 9 and 10. 
 
 EXPERIMENTS WITH HORSES. 
 
 A few of the cases among the horses in 1906 deserve special notice 
 as being typical of the general results of loco feeding. 
 
 Case 16. This horse had been in the loco-free pasture during the 
 season of 1905 and until June 11, 1906. From that time on it was 
 fed Astragalus mollissimus and hay. At first the amount of hay was 
 very small in order to induce it to eat more of the loco, but later on 
 the amount of hay was increased, so that there might be no question 
 in regard to the possibilities of starvation. The animal was kept 
 
 
 650 
 
 600 
 
 1906 MJY 
 
 JULY 
 
 SEPT. 1906 
 
 FIG. 11. Curve of weight of horse No. 16. 
 
 upon this diet until July 21. During this time it lost in weight about 
 60 pounds. It was noticed that it ate the loco in a very variable 
 manner; sometimes very little and at other times very freely. On 
 July 22, as it had become impossible to ob.tain suHicient of the Astra- 
 galus mollissimus, the horse was put in the AragaUus himberti pasture, 
 remaining there until July 31, when it was taken in from the pasture 
 and fed AragaUus lamberti and hay. This diet was kept up until 
 September 19, when tho horso was taken up for treatment, but it 
 continued to grow worse and died September 25. 
 
 In this cose there was decided trouble with the lungs as well as the 
 ordinary loco symptoms. Plate VIII, figures 1 and 2, show the 
 effect of the loco upon the animal. The curve, figure 11, shows the 
 loss in weight. 
 
 Case 50. This was an old horse that had evidently been worked 
 for many years. It was received in the spring of 1906, and on 
 arrival at the station was very poor, weighing only 670 pounds. It
 
 64 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 was placed in the Aragallus lamberti pasture and immediately com- 
 menced to eat more or less of the loco plant. It gained somewhat in 
 weight, weighing 695 pounds on July 18. Plate VIII, figure 5, shows 
 its condition at this time. On September 7, however, it weighed 
 only 660 pounds, having lost a good deal of flesh. It continued to 
 eat AragaUus lamberti until September 16. On this date it disap- 
 peared from the station and was located several miles away, and the 
 attempt to drive it in brought out the fact that it was not only poor 
 but very badly locoed in every way. It was blind in one eye, proba- 
 bly having received the injury by running into a barbed-wire fence. 
 It would walk directly into a fence, not stopping until actually cut 
 by the wire. When driven, it would turn to one side and then move 
 straight ahead, not stopping until it ran against a fence. In order 
 to turn the animal it was necessary not only to get in front of it, but 
 to strike it over the head. It was very poor at this time, but seemed 
 to have a good deal of strength. On September 17 it was driven out, 
 
 FIG. 12. Curve of weight of horse No. 50. 
 
 but showed no sense of direction whatever in regard to the place it 
 should go. Plate VIII, figure 6, shows its condition. The picture 
 also shows very clearly the cuts upon its head which had been caused 
 by running into a barbed-wire fence. 
 
 An attempt was made to treat the animal, but without any effect. 
 On the morning of September 19 it was found dead. It had 
 broken through three corral fences and had fallen down into a hole 
 which had been dug for a cellar. Although the animal was old it was 
 nevertheless strong, and in the early part of the season was in very 
 good condition. Its end was doubtless due to the effect of the loco. 
 Figure 12 gives the curve of its weight. 
 
 Case 52. This was of interest as being one of the few cases of 
 mules experimented upon. The animal was put in the Aragallus 
 lamberti pasture early in the spring of 1906 and at first apparently 
 ate none of the loco. Toward the end of May, however, some two 
 weeks after it had been placed in the pasture, it was noticed that it 
 not only ate AragaUus lamberti freely, but seemed to care for nothing
 
 EXPERIMENTS WITH HOESES, 1906. 
 
 65 
 
 else. At this time it would pick off the leaves, but would not eat the 
 flowers. It passed from one plant to another, eating them with great 
 greediness. On June 18 it was weighed and found to weigh 590 
 pounds, a gain of 40 pounds from the time it was placed in the pas- 
 ture. When weighed on September 7, heavy loss was shown, as it 
 then weighed only 505 pounds. The mule was kept in the AragaUus 
 lamberti pasture, but it was noticed on September 13 that it was not 
 eating at all. Rather to our surprise, on the morning of September 
 15 it was found dead. It was thin, but nevertheless seemed to be 
 quite strong. Plate VIII, figure 3, shows its condition in the spring, 
 when the experiment commenced; figure 4, September 7, shows its 
 peculiar attitude, with all the symptoms of loco poisoning very 
 marked. Text figure 13 gives the curve of weight. 
 
 Case 59. This mare was placed in the loco-free pasture during the 
 early part of the season. She was about 8 years old and never had 
 
 I 
 
 600 
 550 
 500 
 
 1906 MAY 
 
 JUNE 
 
 JULY 
 
 AUGUST 
 
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 FIG. 13. Curve of weight of horse No. 52. 
 
 been broken. She had a peculiar congenital malformation of the 
 fetlock joints. Except for this defect, however, she was entirely 
 sound and healthy. She increased in weight, and when, on July 18, 
 she was placed in the Aragattus lamberti pasture she weighed 885 
 pounds. On September 7 she weighed 830 pounds. During this 
 time she ate comparatively little of the AragaUus lamberti, and on 
 September 18 she was taken into the corrals in order to hasten the 
 effect of poisoning by forced feeding of Araqallus lamberti and hay. 
 This feeding was continued until October 20, when for about a week 
 she was in the Aragattus lamberti pasture. On the 2Sth it was noted 
 that she was getting exceedingly poor and that the nervous symp- 
 toms were very marked. From that time on she was kept in the 
 corral, fed hay and chop, and was treated, the treatment continuing 
 through October and November with no apparent effect. This loss of 
 flesh was particularly noticeable, because when she was taken into the 
 corral to commence the feeding of loco she was an especially smooth, 
 79154 Bull. 11209 5
 
 66 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 handsome-looking animal, and the loco effect came very quickly and 
 in a very marked way. She was taken to Fort Collins in December 
 in order to continue the treatment during the winter, but died on 
 the road. This was a typical loco case, the symptoms were marked 
 and distinct, and the case is particularly interesting because the 
 effect of the poison came in such a short time. Text figure 14 shows 
 the curve of weight. 
 
 EXPERIMENTS WITH SHEEP. 
 
 Through the kindness of local sheep owners near Hugo considerable 
 work on sheep was possible during the season of 1906. These sheep 
 were numbered as received and were kept in the corral nights and 
 herded in the neighborhood of the experimental ranch and on a pas- 
 ture which was pretty well covered with Aragallus lamberti. Some 
 of the sheep were very weak when received and in bad general condi- 
 
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 1906 
 
 M/IY 
 
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 FIG. 14. Curve of weight of horse No. 59. 
 
 tion. During the season 69 were used in the experiment, 63 being 
 bucks a year old and 6 lambs. All were supposed to be locoed at the 
 time when they were received. 
 
 In the early autopsies special attention was paid to the presence 
 of parasites, particularly the grubs of (Estrus ovis. The symptoms of 
 this disease (grub in the head) are very similar to 'the symptoms of 
 loco, and there was a possibility that the so-called locoed sheep were 
 not locoed, but were affected by this parasite. Thysanosoma actini- 
 oides was also found in greater or less numbers in the duodenum or 
 in the bile ducts, or in both. 
 
 Inasmuch as in the former investigations on locoed sheep under 
 the direction of Doctor Marshall, a partial report of which was made 
 in the Johns Hopkins Hospital bulletin, the very definite conclusion 
 was reached that so-called locoed sheep were infested by these two 
 parasites, and that if the parasites were removed the cause of the 
 trouble would also be removed, these early autopsies were particu- 
 larly interesting.
 
 BUL. 112, BUREAU OF AMMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE VIII. 
 
 Case 16, June 6, 1906. Horse before eating loco 
 weed. 
 
 Case 16, September 15, 1906. Animal shown in 
 Fig. 1, in an advanced stage of loco poisoning, 
 emaciated and extremely weak. 
 
 Case 52, May I't, 1V06. Mule in fairly good con- 
 dition before feeding upon loco weed. 
 
 Case 52, September 7, 1906. Mule shown in Fig. 3, 
 in last stages of loco poisoning. 
 
 Case 50, July IV, 1V06. An old horse before being 
 fed with the loco weed. 
 
 Case 50, September IN. 1'W). Same animal as in 
 Fig. 5, showing effect of loco poisoning in atti- 
 tude and emaciated condition ; also shows cuts 
 produced by running into barbed wire fence.
 
 BUL. 112, BUHEAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE IX. 
 
 A group of locoed sheep, showing the general 
 appearance of locoed animals. 
 
 Sheep 27. A locoed sheep in last stages of 
 poisoning. 
 
 Sheep 36. Effect of loco poisoning combined with 
 grub in the head. 
 
 Same as Fig. 3, in a different attitude. 
 
 Case 66, October 20, 1906. A locoed lamb. 
 
 Case 66, November 12. 1<X)6. Attitude of the ani- 
 mal just before its death.
 
 EXPERIMENTS WITH SHEEP, 1906. 67 
 
 If the sheep were affected with loco poisoning it was evident that 
 the effect of the loco was complicated by the parasites, and, of course, 
 it might be possible that the primary trouble was not poison by loco 
 plants, but the effect of these parasites. It therefore seemed desir- 
 able, if possible, to remove the parasites, and thus do away with the 
 sources of complication. In this work of removal, however, the 
 results proved that we were only partially successful. 
 
 Five of the sheep were given gasoline and milk as a vermifuge. 
 Three of these were autopsied, with the result that one was found 
 with many tapeworms, the other two with a few. It would appear, 
 then, that the work of the vermifuge was only partially successful. 
 It may have reduced the number of tapeworms, but it certainly did 
 not clean them all out. 
 
 Four sheep were treated for (Estrus ovi*. In two of these, holes 
 were drilled into the frontal sinuses, and about a teaspoonful of gaso- 
 line injected into each side; they were then washed out with a foun- 
 tain syringe with water containing a little gasoline. Of these two, 
 one was operated upon on May 10 and died August IS, when there 
 were still some individuals of (Estrus ovis in the frontal sinuses. 
 The other was operated upon on May and died the 21st, at which 
 time 8 living grubs and several dead ones were taken out of the frontal 
 sinuses and nostrils. Inasmuch as during the operation of washing 
 out a considerable number of (Estrus ovis were seen to come from the 
 nostrils, it is known that the operation was partially successful. It 
 would appear, however, that in neither case did it entirely rid the 
 animals of the grubs. 
 
 The other two cases were treated by injecting gasoline into (he 
 nostrils. In neither of these, unfortunately, were we able to make 
 autopsies, so that the result of the experiment was not known. 
 
 A similar experiment was tried on some sheep in the season of 
 1007. Sheep Nos. 74, 77, and SO were treated by injection of about 
 a teaspoonful of gasoline into each nostril. One of these was later 
 killed by a coyote. It was autopsied and no grubs were found in the 
 frontal sinuses. Inasmuch as we feel certain of the diagnosis of 
 grub, it would seem that in this ease the treatment with gasoline was 
 successful. Of the two others, No. 77 was in bad condition when 
 treated, but immediately began to get better. No. SO was also in 
 better condition after treatment. It seems probable that in all these 
 cases the gasoline treatment for (ExtniM on* was successful. 
 
 Soon after the first lot of bucks was received in 1(M)(> an experi- 
 ment was made to see whether they would eat loco readily or not. 
 Hay mixed with Anifjnllux lamberti was placed in the corral where 
 the sheep were confined. It was noticed that 1'J of them would eat 
 the weed to some extent. None of them ate very greedily, but
 
 68 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 they would pass by the pile, perhaps pick up a single plant, and then 
 pick up more hay. The others did not eat the plant at all. This pre- 
 liminary experiment seemed to show that none were anxious to eat 
 the loco and that many did not care to eat it at all. As the season 
 went on, however, all of them ate more or. less of the Aragdllus lam- 
 berti in the field, sometimes eating a considerable amount and at 
 other times only eating a little. Inasmuch as sheep have a way of 
 nibbling at anything, it was sometimes rather difficult to tell whether 
 they had a real passion for the weed or not. There were some, 
 however, that would go from plant to plant and devote themselves 
 for at least a portion of the day to eating nothing at all except Ara- 
 gallus lamberti. It was also rather difficult to tell to what extent the 
 animals were affected by the weed. Many of them were rather poor 
 and weak. Some of them were more or less erratic in their move- 
 ments, and as the season went on this became more pronounced. In- 
 stead of keeping together in a bunch as normal sheep do, they would 
 scatter in groups of two or three, while sometimes a single animal 
 would stray off by himself. It thus became increasingly difficult 
 to care for them properly, as it was impossible to keep a herder 
 with them all the time. Sometimes some of them would be lost for 
 a day or two, and some disappeared never to return, having fallen 
 prey to the coyotes. 
 
 Plate IX, figure 1, shows the general character of the sheep 
 received from Mr. Mclntyre in the spring. The cases all resem- 
 bled each other very closely. Attention, perhaps, may be called to 
 two or three of them, with the accompanying illustrations, as show- 
 ing the typical condition of locoed sheep. 
 
 Sheep 27. This was badly locoed when received and lived only a 
 few days. Attention is called to it because the picture (PI. IX, fig. 2) 
 shows the typical appearance of a locoed sheep in the last stages of 
 the disease. 
 
 Sheep 36. This was interesting as being an animal upon which an 
 operation was performed to rid it of (Estrus oms. There seems no 
 question that the operation was partially successful, although not 
 completely so. The sheep was an old buck, perhaps 5 or 6 years 
 old, and, except for his emaciation, was rather a handsome animal. 
 He was kept about a month, when he died, his death without any 
 doubt being the result of the loco poison. Plate IX, figures 3 and 4, 
 show the condition of the animal. 
 
 Lamli 66. In Plate IX, figures 5 and 6, are shown the peculiari- 
 ties of locoed lambs. This was a lamb received in October, and was 
 badly locoed. As the picture shows, the animal was in good condi- 
 tion so far as flesh was concerned. However, it was weak, stagger- 
 ing about in typical loco fashion. Plate IX, figure 6, shows the dull, 
 dozy condition of the animal, the photograph having been taken 
 only a short time before its death.
 
 EXPERIMENTS WITH SHEEP^ 1906. 69 
 
 In 1907, besides a locoed wether presented by the Hamp Brothers, 
 we had 15 bucks brought in by Mr. Mclntyre on June 17. The his- 
 tory of these 15 bucks was of special interest because it differed sc 
 much from that of the sheep brought in by the same owner the 
 preceding year. When they were delivered at the experiment sta- 
 tion they were all poor, some of them staggering more or less as they 
 walked, and they were considered by the owner and other sheepmen 
 who saw them as typical specimens of locoed sheep. They resem- 
 bled in their general appearance very closely the sheep that were used 
 for experiment in 1906. From the very beginning, however, their 
 behavior was different. While those of 1906 would feed where loco 
 was abundant, confining their pasturage very largely to such localities, 
 those of 1907 sought the lower land, where there was no loco but more 
 grass, and even when the loco was abundant about them they paid 
 very little attention to it. While the sheep of 1906 would scatter, 
 going off in groups of two or three or individually, those of 1907 kept 
 together and behaved more like normal animals. They were fed a 
 little grain daily, mainly to accustom them to have a habit of coming 
 to the corrals at night, but not enough to make any great difference 
 in the formation of flesh. Nearly all of them gained through the 
 summer, and were returned to the owner in good condition. 
 
 A few of these sheep, as explained elsewhere, were treated for 
 (Esirus ovis. Most of them had discharges from the nose, in many 
 cases bloody, and it is possible that the real trouble with the band 
 was not loco but the grubs of (Estrus ovis. As is well known, animals 
 generally recover from attacks of this grub, and it may be that the 
 improvement of the sheep in question was due to the loss of the 
 grubs in the course of the summer. 
 
 There is no doubt that nearly all of the sheep which were kept at 
 the ranch in 1906 were locoed, and just as little that few if any of 
 the band received in 1907 were affected by the loco poison. The 
 experiments with sheep were, therefore, of particular interest us 
 showing how easily the effects of grub in the head ma}' be confused 
 with loco poisoning. Incidentally, it would appear from our work 
 that the injection of gasoline into the nostrils of sheep that are 
 infested with the grub of (Estrus ovin is likely to be followed with 
 excellent results. 
 
 DI8CUMION OK THK SHKKP EXPERIMENTS. 
 
 Sixty-three of the 69 sheep used in the experiment of 1906 were 
 bucks a year old or more, and 6 were lambs. All were supposed to be 
 locoed when they were received. Autopsies were held upon 33 of the 
 cases. In the autopsies special attention was paid to the presence 
 of parasites because of the conclusions reached by Doctor Marshall, 
 which have already been summarized in the discussion of the lit- 
 erature. Of the 33 on which autopsies were held, 23 had grubs of
 
 70 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 (Estrus ovis. These were present in some cases in considerable 
 numbers, and their presence was indicated before death by a bloody 
 discharge from the nostrils. One case, No. 23, was considered to have 
 died as the result of the presence of this grub. Twenty- three of the 
 33 were infected with TJiysanosoma actinioides. In most cases, 
 however, this tapeworm was not present in large numbers. In 
 some the bile ducts were much distended with them, but commonly 
 the numbers were rather small, and perhaps not more than would 
 be expected in an animal which is so subject to parasitic infection. 
 Cysticerci were found in 6 of the cases, but there is no reason to think 
 that they affected the animals injuriously. In 13 of the post-mortem 
 cases the inner walls of the fourth stomach were inflamed; 9 had 
 blood clots in the lateral ventricles; 15 had an apparently abnormal 
 number of hemolymph glands in the dorsal parts of the thorax, or 
 the abdominal cavity, or both, and in 18 there was a serous coagulum 
 present in the epidural space of the spinal canal. 
 
 In the experiment of 1907 most of the sheep were not seriously 
 affected by the loco poison, but were suffering from other causes, the 
 evidence tending to show that the presence of (Estrus ovis was in 
 part at least responsible for their condition. The principal diffi- 
 culty with most of the animals in 1906 was the loco poison, with 
 the effects complicated by parasites. On the other hand, it seems 
 that the chief trouble with most of the sheep in 1907 was caused by 
 the parasites and that the loco had little if anything to do with their 
 condition. It is evident from our work that it is very easy to confuse 
 the effects of parasites with those of loco poisoning. The general 
 appearance of the bands of sheep in 1906 and 1907 was the same, 
 and not only the author, but experienced sheepmen, declared that 
 both bands were locoed. In the majority of cases it was only by 
 post-mortem examination that the diagnosis could be confirmed. 
 These statements refer, of course, to the general symptoms. If the 
 habits of the sheep are observed there is a marked difference. The 
 sheep affected with (Estrus ovis, except when they are in very bad 
 condition, keep together like normal animals, and show a preference 
 for good food, although they may at times eat loco. The locoed 
 sheep, on the other hand, are more erratic, and develop a solitary 
 habit to a greater or less extent. They show, too, a marked fondness 
 for the loco weed. At the same time, when one is dealing with a con- 
 siderable number of sheep, it is a matter of much difficulty to separate 
 the locoed animals from those affected with grub in the head. It is 
 not strange that in experiments where sheep only have been used 
 those in charge have been led to the belief that the so-called locoed 
 sheep are sheep infested with parasites, for the symptoms bear a 
 close resemblance. Moreover, it is very possible that in individual 
 experiments the supposed locoed sheep were in fact not locoed at all.
 
 EXPERIMENT AT WOODLAND PARK, COLO. 71 
 
 It is a matter of considerable interest that lambs are much more 
 quickly affected than older animals. Attention was first called to 
 this fact by Mr. A. Mclntyre, who stated that lambs would frequently 
 succumb to the poison in two or three weeks, and with little loss of 
 flesh. The author's observations were completely confirmatory of 
 this statement. Of the 6 lambs under observation (Nos. 65 to 70), 
 all were in good flesh, but very distinctly locoed. Post-mortems 
 were held on 5 of these, and the results were very interesting. All 
 had clots in the lateral ventricles. All had serous coagulum in the 
 spinal canal, and all had congested walls of the fourth stomach. 
 This would seem to confirm our opinion that these lesions are charac- 
 teristic of the locoed condition, but that in chronic cases they may be 
 more or less masked. 
 
 EXPERIMENT AT WOODLAND PARK, COLO. 
 
 The loco conditions were so different in the mountains that it 
 seemed wise to conduct a feeding experiment to determine to what 
 extent the phenomena would differ from those in the plains. The 
 loco plants grow in the mountains to an elevation of 8,000 to 10,000 
 feet, and among the stockmen pasturing horses and cattle in these 
 localities there are plenty of stories of locoed animals. The prin- 
 cipal loco plant in the region where the experiment was carried on is 
 Aragallus lamberti, but with this are associated a great many plants of 
 Astragalus nitidus and a smaller number of Astragalus splendem. In 
 the summer of 1906 land was offered for an experiment between 
 Woodland Park and Divide, on the Colorado Midland Railroad. A 
 particularly thick field of loco was fenced in for a loco pasture, and an 
 adjoining piece with very little loco was used as a control pasture. 
 Eleven horses and 12 head of cattle were used in this experiment, 
 6 of the cattle being donated by the Crescent Cattle Company, of 
 Cripple Creek. 
 
 The horses were put in the pasture July 13 6 in the loco pasture 
 and 5 in the control pasture. A week later 6 head of cattle were 
 received and were divided, one-half being put in each pasture. On 
 July 27 horses 73 and 74 were taken into the corral, where they were 
 kept through the rest of the season, and fed on cut loco, with an abun- 
 dance of hay. On August 14, 6 more cows were received and were 
 divided between the two pastures. The cattle ate loco readily, and 
 before the season was over cleaned out the pasture pretty thoroughly. 
 The horses would not eat loco in the field, but those in the corral ate 
 quite freely. None of the cattle showed any positive effects as the 
 result of the loco eating. The horses in the corral grew thinner, 
 became dull, and showed a somewhat stiffened gait. The lack of more 
 general results in this feeding experiment was due in part probably 
 to the comparatively short time during which the experiment was
 
 72 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 carried on. It was unfortunate that we were unable to install the 
 experiment earlier in the season. 
 
 The animals remaining in the fall of 1906 were taken to the ranch 
 of the Crescent Cattle Company, where they were kept during the win- 
 ter, receiving the ordinary treatment of the range stock owned by that 
 company. During the winter horses 73 and 74 died, their death 
 doubtless being occasioned by the weakness produced by the loco 
 poison during the preceding summer. 
 
 In 1907, 8 horses and 8 cattle were pastured at Woodland Park; 
 part of these, as in the preceding season, were kept in the loco pasture 
 and part in another past -, Comparatively free from loco. It was 
 found, however, as the season progressed, that the so-called loco-free 
 pasture had considerable of the plant in it, and some of the animals 
 which were pastured in it became locoed in spite of the small tempta- 
 tion. As in the preceding season, we were unfortunate, because of a 
 series of events entirely beyond our control, which made it impossible 
 to start the real experiment until comparatively late. 
 
 The animals ate the loco readily, but none of the cattle were clearly 
 locoed. Horse 76 was put in the loco pasture on June 11, and was 
 badly locoed on August 6. This locoed condition was evident in her 
 extremely nervous manner. She was easily startled and ate in a 
 nervous way, as if frightened. She had the high step peculiar to 
 locoes and the straddling attitude of the hind legs when she walked, 
 and would rear when startled. At this time, however, there was no 
 loss of flesh, but toward the end of August she showed a distinct loss 
 of flesh, and on August 31 was taken up for treatment, the result of 
 which is given elsewhere. 
 
 At the end of the season the stock was taken to Hugo to be pas- 
 tured during the winter. At this time 5 of the 8 horses were dis- 
 tinctly locoed, but none of the cattle showed the effects of the poison. 
 
 The principal result of the two years' feeding at Woodland Park 
 seemed to indicate that stock is not as easily locoed in the mountains 
 as in the plains, and that horses are much more easily locoed than 
 cattle. The latter fact seems to be in harmony with the results of 
 experience, for there are very few complaints of locoed cattle in the 
 mountains. A number of factors may explain the smaller number of 
 locoed horses in the mountains. The loco is not so abundant as in 
 the plains, commonly being restricted to smaller areas, while the grass 
 is more abundant and commonly does not dry out, as it does on the 
 plains, so that the animals are not forced upon the loco because of 
 lack of other food. It is very possible, too, that the amount of the 
 poison in the mountain loco is not as great as in the plants of the 
 plains. This can only be determined by extensive laboratory experi- 
 ments, for which thus far there has been no opportunity.
 
 REMEDIAL MEASURES. 73 
 
 ' EXPERIMENT AT IMPERIAL, NEBR. 
 
 This experiment was carried on in cooperation with the experiment 
 station of the University of Nebraska, which was represented in this 
 work by Dr. A. T. Peters. The work was located at Imperial, in the 
 southwestern part of Nebraska, and the animals for the experiment 
 were donated by local stockmen. The loco in this section consists 
 almost entirely of Astragalus moTlissimus. The work was under the 
 immediate supervision of Mr. L. B. Sturdevant, of the University of 
 Nebraska. 
 
 In this feeding experiment the attempt was made to get results from 
 the loco as rapidly as possible. With this end in view the animals 
 were herded on the loco part of the time, and part of the time the 
 weed was cut and fed to them. In the feeding experiments hay was 
 always used as well as the loco, in order that there might be no ques- 
 tion of starvation. The work was started about July 4 and was car- 
 ried on to the end of October, when all the animals eating loco were 
 dead. Only horses were used in this experiment, and the number was 
 unfortunately much too small. All contracted the disease, however, 
 and died with the typical symptoms of locoed animals, showing the 
 same post-mortem phenomena as were exhibited in the animals 
 studied in Colorado. Careful post-mortems were made, and the gen- 
 eral results of the work served to confirm that carried on at Hugo. 
 Tli us the work in Colorado was supplemented in an important way, 
 for it was impossible during the season of 1906 to obtain in the neigh- 
 borhood of Hugo very much of the Astragalus moUissimus for feeding 
 experiments. 
 
 REMEDIAL MEASURES. 
 
 In the work of the first season no attempt was made to experiment 
 with remedies for the loco disease. The knowledge of the subject 
 was so indefinite that there seemed to be no adequate foundation for 
 such work. It seemed better to devote all our energies to getting a 
 diagnosis of the disease and determining its cause before attempting 
 to apply any remedies. 
 
 During the second season, however, it appeared that tho correct 
 diagnosis of the disease was gradually being evolved as the result of 
 our observations, and it seemed best to make some tentative experi- 
 ments with remedies. Inasmuch as most locoed animals are con- 
 stipated, it was clear that something to produce free action of the 
 l>owels was of first importance. This would be true not only be- 
 cause it was desirable to have healthy action of the intestines, but 
 l>ccause it would be presumed that a free action of the bowels would 
 aid in eliminating whatever poison had boon absorbed. Tho remedy 
 used for this condition of constipation was magnesium sulphate.
 
 74 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 When this was first used, the chemistry of the loco plant had not 
 been worked out, and the reason for its use was simply to correct 
 constipation. As it turned out later from the laboratory work, 
 in this substance we were using the most probable antidote for 
 the barium poison. This information, however, came too late to 
 make it possible to experiment with antidotes. It would seem pos- 
 sible to arrange to give small doses of a sulphate which should 
 neutralize the effects of the extremely small amounts of barium 
 in the loco. Doctor True has suggested that this might be done in 
 connection with salting the stock. It may be that through the food 
 or drink it will be possible to give enough of an antidote, so that 
 whatever effect the barium has may be nullified. Further experi- 
 ments to this end will be made. 
 
 The effects of loco poisoning come on very slowly as a rule and after 
 a long period of feeding. This period may not only be many days, 
 but frequently months, and in some cases even years. The locoed 
 condition seems to be the accumulated effect of a multitude of small 
 doses of the poison, and the cure of the animals would most probably 
 be sought in a treatment of the general condition of the animal rather 
 than in any special treatment to counteract the effects of the poison. 
 The most marked symptoms of locoed animals are the nervous phe- 
 nomena and the anemia. These conditions were those that were 
 especially considered in planning remedies. It seemed wise to pay 
 more attention to building up the animals than to attempt to use an 
 antidote. Several remedies were used which were clearly proved to 
 be useless. One of these was potassium iodid, with which a fairly 
 thorough trial was made. Asafetida, valerian, and caffein were 
 tried, but with no good results. Strychnin seemed a logical remedy 
 for the most evident symptoms, and was tried with a number of ani- 
 mals with varying results. Nine head of cattle, 3 horses, and 5 sheep 
 were treated with this remedy. Most of those treated were in bad 
 condition, and it was a fair question whether in any of these cases 
 unfavorable results should not have been expected, or, rather, whether 
 they would not have died in spite of all treatment. Two of the cattle 
 made somewhat remarkable recoveries. 
 
 Two of the cattle were cured during the strychnin treatment and 
 there seemed no good reason why this drug should not have the 
 credit of the cure, but it was true that other animals treated with 
 strychnin died, in some cases partly, at least, as the result of the 
 poison. None of the horses showed improvement from the use of 
 strychnin. The fact that several of the animals showed indications 
 of poisoning made it probabhe that strychnin was administered in too 
 large doses, although only the minimum doses of the ordinary veteri- 
 nary materia medica were used. It seemed probable that locoes
 
 TREATMENT WITH STRYCHNIN IN 1906. 75 
 
 perhaps were more sensitive to the effects of the drug and should be 
 treated in especially small doses. 
 
 Arsenious acid effected a cure in one of the horses. This animal 
 was treated at the agricultural experiment station during the winter 
 of 1906-7 under the general direction of Doctor Glover, and while it 
 was a clear case of loco in the fall of 1906 with all the typical symp- 
 toms, it came out hi the spring definitely and apparently permanently 
 cured. This animal was used as a saddle horse during the summer of 
 1907 and at no time showed any of the signs of loco poison, if we except 
 a slight loss of spirits. 
 
 One of the cattle, too, after it was treated with Fowler's solution, 
 was completely cured. 
 
 TREATMENT WITH STRYCHNIN IN 1906. 
 
 Case 4 was a steer that had been kept in the loco-free pasture during 
 the season of 1905. In 1906 it was at first placed in the loco-free 
 pasture, but on May 3 was put in the AragaUus lamberti pasture, 
 where it commenced to eat the weed and continued to eat it with 
 considerable freedom. Gradually the poison began to show its effect, 
 and by the latter part of August the animal was recognized as a typical 
 loco. It was in excellent condition at the beginning of the season, 
 when turned into the AragaUus lamberti pasture. Plate X, figure 1, 
 shows its condition May 30, 1905; figure 2, taken September 7, 1906, 
 shows its condition on that date, when it was very distinctly under the 
 influence of the poison. In this picture the attitude is that of the 
 typical loco. It had lost flesh and showed nervous symptoms in the 
 way of responding with convulsive movements to sudden sounds, and 
 when made to run its head would shake with the palsied movement 
 which is characteristic of many locoed cattle. In figure 3 may be 
 seen the serous sac under the jaws, one of the typical symptoms of 
 loco poisoning in cattle. The steer was taken up on September '20 
 for treatment and was given daily one-quarter grain of strychnin 
 hypodermically until September 30, when the dose was increased to 
 one-half grain. During this time it did not gain in weight, but the 
 nervous phenomena gradually disappeared. The doses were kept up 
 until October 6. From that time until the end of the. season it was 
 kept in the loco-free pasture. When it was sent away for the winter 
 on November 'JO it seemed to have entirely recovered so fur as 
 nervous symptoms were concerned. Figure 4 shows the animal's 
 condition August 22, 1907. 
 
 The curve of weight for 1906 (text fig. 15) shows that this steer 
 did not make normal gains. The loss for the end of October and for 
 November, however, is the normal result for that time of the year. 
 Storms and shortness of food caused losses that year in all the ani-
 
 76 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 mate at that period. In the spring of 1907 the animal was kept in the 
 loco-free pasture about one week. During the rest of the summer it 
 was kept in the good pasture until September 18. From this time until 
 October 28 it was herded on loco. As the curve shows (fig. 16), it 
 gained during this time about 300 pounds. Plate X, figure 4, 
 shows that on August 22, 1907, while in the loco-free pasture, the 
 
 FIG. 15. Curve of weight of steer No. 4, 1900. 
 
 animal was in fine condition. When it was kept on loco, however, it 
 ate freely and at the close of the season it again showed distinct symp- 
 toms of loco poisoning, although it was not a bad case. 
 
 Another case, No. 536, was a Hereford steer belonging to Mr. 
 Mattix, of Hugo, which was brought to the station for treatment on 
 July 9. It was at this time extremely poor, its coat was rough, its 
 
 1200 
 1150 
 MOO 
 1050 
 1000 
 950 
 
 \9Q74PWl 
 
 MAY 
 
 juue 
 
 V 
 
 JULY 
 
 OCr. 1907 
 
 FIG. 16. Curve of weight of steer No. 4, 1907. 
 
 eyes staring, and it stood with head low and legs spread apart because 
 of evident weakness, and with a peculiar curvature of the fetlock 
 joints of the hind feet which is sometimes noticed in locoed animals. 
 Plate X, figure 5, shows very clearly the condition of the animal at 
 this time. It appeared a hopeless case, because the animal not only 
 showed the effects of poison, but was extremely weak. It was kept 
 in the corrals, as it was too weak to be sent out into the pastures.
 
 BLL. 112, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE X. 
 
 Case 4, May 30, 1905. Before feeding on loco 
 weed. 
 
 Case 4, September 7, 1905. Showing all the typ- 
 ical symptoms of loco poisoning. 
 
 Case 4, September 15, 1906. Animal under influ- 
 ence of loco and with a noticeable accumulation 
 of serous fluid under chin. 
 
 Case 4, August 22, 1907. Same animal as in 
 Figs. 1 to 3, in the succeeding year, when it 
 no longer showed symptoms of loco poisoning. 
 
 Case 536, July 9, 190f>. A locoed itecr with curva- 
 ture of the fetlock joints, which is peculiar to 
 some locoed animals. 
 
 Case 536, July 25, 1906. The same animal after 
 treatment with itrychnine. It stands in nor- 
 mal fashion and has gained much in strength 
 and in weight.
 
 TREATMENT WITH STRYCHNIN IN 1906. 77 
 
 It was fed upon alfalfa hay and some grain, and was given hypo- 
 dermically one-half grain of strychnin daily. The strychnin seemed 
 to take effect upon it almost immediately and on July 1 1 its fetlock 
 joints had straightened out and the animal showed itself in every 
 way very much improved. The doses of strychnin were kept up 
 from July 9 until July 21. Most of this time the action of the bowels 
 had been very free, but as at this time it seemed somewhat consti- 
 pated, it was given 250 grams of Epsom salts, and was turned into 
 the loco-free pasture, where it was kept until July 30, when it was 
 brought in and given another course of strychnin, one-half grain 
 daily until August 6, when it was again turned into the loco-free 
 pasture and was considered as very nearly cured. Plate X, figure 6, 
 shows its improved condition on July 25. About October 1 it was 
 turned back to the owner, who sent it out upon the range with his 
 other cattle. The animal was seen again about the end of October 
 and it was evident that the cure was complete and permanent. Later 
 in the season the steer was put upon the market. 
 
 Case 40 was also treated with strychnin. This was a large, hand- 
 some steer which was received in the spring and kept in the loco-free 
 pasture until July 18, when it was placed in the Aragallus lamberti 
 pasture. It immediately commenced to eat the loco, and from this 
 time on ate it with rather unusual freedom, seeming to prefer it to 
 grass. The daily notes taken by the observers in the pasture indicate 
 that it ate loco rather more freely than any of the other cattle. Its 
 weight was 1,235 pounds when put in the Aragallus lamberti pasture. 
 It gradually lost weight, and on October 16 weighed 1,160 pounds. 
 Shortly after this the loco symptoms became very marked. The 
 peculiar condition of the hind fetlock joints which was noticed in No. 
 536 was very marked in this animal also. At the end of October the 
 steer was taken up for treatment. At this time 'it weighed 1,105 
 pounds. It was treated hypodermically with one-half grain strychnin 
 daily and fed in the corrals with hay and chop. This treatment 
 was continued until November 5. On November 12 its weight was 
 1,025 pounds. It was taken from Hugo to Fort Collins to continue 
 treatment through the winter. From December 9 until December 
 20 it was given one-half grain of strychnin dully and showed a slight 
 gain in weight. The treatment was then discontinued for a time, 
 but was commenced again December 2S and continued in doses every 
 second day until January 9. On January 31 it weighed 1 ,210 pounds. 
 Two weeks later it had increased to 1,300 pounds. It was fed, of 
 course, with considerable care, and on February 23 was sold for fat 
 beef. It was at that timo in fino condition. The curve, figure 17, 
 shows the relation of the changes in weight to the feeding of loco and 
 treatment.
 
 78 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 During the season of 1906 none of the horses treated with strychnin 
 showed any improvement, and the same can be said of the sheep. 
 It mav be stated that the doses of strychnin in the case of both horses 
 and cattle were either one-quarter or one-half a grain, and in the case 
 of the sheep from two-twentieths to eight-twentieths of a grain. 
 
 There was no question that in some cases there were symptoms of 
 strychnin poisoning, and this was true of cattle, horses, and sheep. 
 It seemed probable that the doses of strychnin were too large, so that 
 in the weakened nervous condition of the animals they were affected 
 unfavorably. It appears that locoed cattle may be unusually sus- 
 ceptible to the influence of strychnin. At the same time the ex- 
 tremely favorable results in the cases of Nos. 4, 536, and 40 made it 
 seem desirable to make further experiments w4th strychnin, but with 
 the use of much smaller doses. 
 
 1250 
 
 1150 
 1100 
 
 1906 
 
 M4Y 
 
 Jt//Vf 
 
 JUIY 
 
 /WGi/sr 
 
 SffTfMffCff 
 
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 FIG. 17. Curve of weight of steer No. 40. 
 TREATMENT WITH ARSENIC IN 1906. 
 
 Arsenic either in the form of Fowler's solution or of arsenious acid 
 was used with 3 horses, 4 cattle, and 4 sheep. Two of the horses 
 died, one (No. 58), a mare, was cured. The history of this case is 
 given in some detail. 
 
 The mare was received from the Fort Collins Agricultural Experi- 
 ment Station on May 18, and was placed in the loco-free pasture. 
 Her weight at this time was 655 pounds. She had been an old saddle 
 horse, was a lively, spirited animal, although not young, and in June 
 was used as one of the saddle horses at the station. It was found, 
 however, that her nervous disposition made her somewhat unde- 
 sirable for general work, and on July 30 she was put in the Aragallus 
 lamberti pasture and kept there until October 9. During this time 
 there is no evidence that she ate any of the loco weed. Apparently 
 she devoted herself entirely to grass. On October 9 she was taken 
 into the corral and fed cut Aragallus lamberti and hay. At this time
 
 TREATMENT WITH ARSENIC IN 1906. 
 
 79 
 
 she weighed 765 pounds. She was kept during the remainder of the 
 season upon this treatment. 
 
 After October 16 the mare gradually lost in weight and on Novem- 
 ber 12 weighed only 705 pounds. At this time she was weak and in 
 her peculiar nervous actions showed very decided loco symptoms. 
 She would start at sudden noises and would rear when any sudden 
 motion was made near by. She was taken to Fort Collins for treat- 
 ment during the winter, under the general direction of Doctor Glover. 
 It was reported from there on December 14 that she was very badly 
 locoed. She reared when excited, and could not be led or tied. This 
 in spite of the fact that she was a so-called gentle horse and had been 
 used for several years. On December 1 6 treatment was commenced 
 by giving her 2 grains of arsenious acid in chop. This treatment was 
 continued until January 8. On January 9 she weighed 805 pounds, 
 which was a very marked gain, as on December 12 she weighed only 
 740. On March 1 she weighed 865 pounds. It was reported at this 
 
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 1906 W 
 
 JUNF 
 
 Ml* 
 
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 FIG. 18. Curve of weight of horse No. 58. 
 
 time that the man in charge of her tried to ride her, but could not 
 manage her well, and that she would not lead. Her legs were slightly 
 swollen on this date, probably from an overdose of arsenic. No 
 further treatment was given beyond good feed, and she was taken to 
 Hugo in the middle of April and placed in the loco-free pasture. For 
 about a week in May she was herded upon AragaUus Itimberti and ate 
 it with some freedom. She was then put back in the loco-free pasture, 
 having shown no symptoms of poisoning, and a little later, May 10, 
 was arain used as a saddle horse. It was found that she was entirely 
 
 O ** 
 
 reliable and showed none of the symptoms of loco poisoning, if \ve 
 except a slight lack of spirit. She was used during the whole summer 
 in the general work of the station as a saddle horse and did the work 
 well. This was an evident case of cure and presumably the arsenic 
 was instrumental in effecting it. Unfortunately we have no good 
 pictures showing the progress of the disease and cure of this animal. 
 The curve (fig. IS) shows her changes in weight while under treatment. 
 Of the horses that died while being treated with arsenic, one was a 
 very bad case and probably could not have been saved by any
 
 80 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 method of treatment. The other was a good case for treatment, but 
 died in spite of all that was done for her. This case (No. 59) became 
 worse very rapidly, there being only eighteen days of treatment with 
 Fowler's solution before the animal died. It may be considered, per- 
 haps, as a case of rather acute poisoning. 
 
 Of the sheep treated with Fowler's solution, all but one died, and 
 we did not feel at all certain that the cure of this one was due more to 
 the Fowler's solution than to the effect of good food. 
 
 Of the cattle treated with Fowler's solution, all but one died. The 
 one cured (No. 28) was an old milch cow which was received from 
 Denver and at first placed in the loco-free pasture. She was kept 
 there until June 18, when she was brought into the corrals and fed 
 on Astragalus mollissimus. At that time she was heavy with calf, 
 and inasmuch as the loco weeds are popularly supposed to produce 
 
 abortion, it was de- 
 sired to feed this 
 animal loco to see 
 whether any effect 
 would be produced 
 on the birth of the 
 calf. She was fed 
 in the corral from 
 June 18 until July 
 22, with the excep- 
 tion of occasional 
 days in the loco 
 pasture, her rations 
 consisting of fresh- 
 cut Astragalus mol- 
 lissimus and hay. 
 
 She ate both with very great freedom and showed a strong appe- 
 tite for the loco weed. By the end of July it was necessary to 
 terminate the experiment with the Astragalus mollissimus because 
 it was found impossible to obtain enough for feeding purposes, 
 and on August 2 we commenced feeding her hay and fresh-cut 
 Aragallus lamberti. It was noted on August 7 that she showed 
 no effects from the loco feeding, but on the 14th the effects began 
 to appear. She dropped her calf on August 20. Her calf was 
 small and weak, but was fully matured. Whether its weakness 
 could be considered as the effect of the loco is a matter of doubt. 
 The cow was kept in the corral and fed Aragallus lamberti and 
 hay until September 17. During this time the effect of the loco 
 poison became more and more evident. Figure 19 shows the con- 
 dition of the animal on August 27. At this 1 time the serous sac 
 under the jaw, typical of many locoed animals, was very promi- 
 nent. She was put in the loco-free pasture on September 18 and 
 
 FIG. 19. Case 28, August 27, 190ti. Cow after it has become locoed, but 
 not a bad case. The serous sac under the chin is very prominent.
 
 RESULTS OF TREATMENT IN 1906. 
 
 81 
 
 kept there with no further treatment until October 31, in order to 
 see whether simply having good feed and being taken away from 
 the loco might not bring about her recovery. During this time she 
 had gained slightly in weight at first and then lost. On November 3 
 we commenced treating her with 15 c. c. of Fowler's solution daily. 
 This treatment was continued until the end of the month, when she 
 was taken to Fort Collins for further treatment during the winter. 
 During the latter part of December she was treated with potassium 
 iodid, but with no particularly good effect. On February 1 treat- 
 ment with Fowler's solution was resumed and she received 15 c. c. 
 daily through the month. Later the treatment was discontinued. 
 About the middle of March she was shedding her winter coat and 
 getting fat, and the last of March she was fat enough for beef. 
 
 This was evidently a cure, and the credit of the cure must be 
 given to Fowler's solution. The after history of No. 28 is inter- 
 esting, as she was kept during the summer of 1907 upon a pasture 
 
 
 
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 FIG. 20. Curve of weight of cow No. 28, 1906. 
 
 where loco was very abundant and ate more or less of it through 
 the season, but without any noticeably deleterious effects. The 
 curves (figs. 20 and 21) show the changes in weight in the two 
 seasons in their relation to the treatment. 
 
 RESULTS OF TREATMENT IN* 1906. 
 
 In summing up the general results of the reined in 1 measures 
 attempted in 1906, it seemed quite clear that of all the remedies 
 with which experiments were made success had been reached with 
 only two strychnin and Fowler's solution. The marked cases of 
 euro in cattle with strychnin seemed to make it very probable that 
 this remedy would prove useful. It also was evident from the 
 deaths which occurred from the use of strychnin that it would be 
 necessary to use very much smaller doses. 
 
 The results from Fowler's solution were somewhat doubtful. 
 We have the cases of horse No. 58 and of cow No. 28, which presuma- 
 bly were aided in their recovery by the use of the solution. 
 79154 Bull. 11209 6
 
 82 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 Simply a statement of the number of cases in which there was a 
 cure or a failure to cure would hardly give a fair idea of the results 
 of these experiments, but in each case the individual peculiarities 
 of the patient should be considered. As a matter of fact, in most of 
 the cases which were subjected to treatment in 1906 the disease was 
 very far advanced, so that the chances of cure with any course of 
 treatment were very small. This was true in nearly all the cases 
 of sheep and in most of the horses and cattle. The recoveries came 
 only after a somewhat prolonged course of treatment. One of the 
 cattle which recovered was treated forty days, another twenty- 
 seven days. A horse which recovered on a treatment of arsenious 
 acid was treated for thirty days. From the summer's work it 
 seemed wise to experiment further with strychnin and arsenic, 
 
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 1907/f/ff/Z 
 
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 252 
 
 
 FIG. 21. Curve of weight of cow No. 28, 1907. 
 
 using the former mainly with cattle and the latter for the most 
 part with horses. 
 
 During the summer of 1907, then, it was determined to make as 
 fair a trial as possible of strychnin and arsenic, using smaller doses 
 of the strychnin. Inasmuch as some success had been obtained with 
 arsenious acid and Fowler's solution, experiments were made with 
 atoxyl and sodium cacodylate, it being thought that other forms 
 of arsenic might have the same good effects. It may be remarked 
 that the pathological lesions of locoed animals are surprisingly like 
 those produced by the trypanosomes, and, granted that the use of 
 atoxyl in trypanosomiasis succeeds not only because of its specific 
 effects on the parasites but also because of its effect on the system 
 generally, it might be possible that in atoxyl there would be a remedy 
 also for the condition found in locoes. Sodium cacodylate was used 
 because of the marked benefits sometimes produced in cases of ane- 
 mia in human patients.
 
 EXPERIMENTS WITH REMEDIES, 1907. 83 
 
 TREATMENT OF CATTLE IX 1907. 
 
 Fowltr's solution. Only one of the cattle (No. 565) was treated 
 with Fowler's solution. It was a typical loco, although not extremely 
 poor, and the nervous symptoms were not as pronounced as in some 
 cases. The solution was given in 15 c. c. doses and was continued for 
 fifty-three days. The steer gained, but quite slowly. Its weight at 
 the beginning of treatment was 580 pounds, and when it was dis- 
 charged it weighed 670 pounds. It was considered a cure, but the 
 results of Fowler's solution did not seem to be as marked as those 
 that were obtained with strychnin. 
 
 Atoxyl. Atoxyl was used in three cases Nos. 42, 546, and 558. 
 No. 42 was one of the station animals that had eaten loco during a 
 considerable portion of the preceding season, but did not show marked 
 symptoms of loco poisoning. This steer was herded upon loco from 
 the beginning of the season in 1907 until the 1st of August. As early 
 as July 4 it was noted that the animal was holding its head low in the 
 typical loco fashion and that the movements of its legs were somewhat 
 nervous and jerky. A few days later the steer had the staring look 
 in the eyes which is seen in so many locoes and the bending of the 
 fetlock joints of the hind legs. It was kept, however, on the loco 
 until August 1, when it was taken in for treatment. At that time 
 the loco symptoms were very pronounced and the animal was quite 
 weak. It was given 0.28 gram atoxyl and this amount was increased 
 in succeeding days until a maximum of 1.4 grams was reached. This 
 was given until September 2. When the treatment commenced, on 
 August 2, the steer weighed 840 pounds. At the conclusion of the 
 course of treatment the weight was 888 pounds. From that time the 
 animal was kept in the loco-free pasture and gradually increased in 
 weight until the end of October, when it weighed 960 pounds. Before 
 treatment it had the typical dejected attitude of the loco and (lie 
 peculiar flexing of the fetlock joints of the hind legs, but recovered so 
 that it was bright and walked in normal fashion. This case can be 
 considered as a cure, and the credit of the cure probably can be given 
 to atoxyl. The curves (figs. 22 and 2.3) show the changes in weight in 
 the history of the animal. 
 
 No. 546 was treated for a time with atoxyl and afterwards with 
 strychnin, as there seemed to be no gain from the atoxyl. The gain 
 under strychnin in this case was slight. 
 
 The third case which was treated with atoxyl (No. 558) was a bad 
 case from the start, and probably no remedy would have succeeded 
 in bringing the animal out. 
 
 Sodium cacodylate. Five of the cattle were treated with sodium 
 cacodylate, and 4 of these (Nos. 3, 6, 35, and 548) were cured. The 
 one not cured (No. 559) was in the last stages of the disease and 
 probably beyond any cure.
 
 84 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 No. 35 was a cow belonging to the experiment station which had 
 been eating AragaUus lambcrti during the season of 1906, but did not 
 seem to be affected by the poison. During 1907 she was herded upon 
 loco from the first of the season and ate the weed quite freely. On 
 July 1 she was taken in for treatment, as at this time she showed verv 
 
 I 
 
 850 
 600 
 750 
 700 
 650 
 600 
 
 1906 
 
 M4V 
 
 JU 
 
 we 
 
 JULY 
 
 /H/6 
 
 vsr 
 
 Sf/rz 
 
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 1906 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 r/MG/U 
 
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 KGMtt 
 
 1 
 
 V M*m_ 
 
 FIG. 22. Curve of weight of steer No. 42, 1900. 
 
 distinct signs of being locoed. For a considerable time before this 
 she had been constantly losing weight. She was given 0.6 gram of 
 sodium cacodylate hypodermically. This treatment was continued 
 from July 1 to August 10. Her weight just before the treatment 
 commenced was 792 pounds. At the time the treatment ceased she 
 
 I 
 
 950 
 
 900 
 850 
 600 
 
 1907 JPfVL 
 
 MJY 
 
 /H/Gvsr 
 
 S&TEtfetA 
 
 OCr 1907 
 
 FIG. 23. Curve of weight of steer No. 42, 1907. 
 
 weighed 882 pounds. From this time she was kept in the loco-free 
 pasture and at the end of October weighed 990 pounds (see fig. 24). 
 No. 548 was a heifer belonging to Mr. Woods, of Hugo. She was 
 brought to the station from the Woods ranch on April 22. She was 
 very thin and wild eyed and when eating showed in a marked way 
 the peculiar stiff action of the jaws which is frequently characteristic
 
 TREATMENT OF CATTLE IN 1907. 
 
 85 
 
 of locoed animals. She was given a few doses of magnesium sulphate 
 and three-twentieths of a gram of strychnin was administered hypo- 
 dermically from April 23 to April 27. From this date sodium cacody- 
 late was given hypodermically in 0.3-gram doses, and the treatment 
 was continued until May 13. The dose was increased to 0.4 gram 
 
 1000 
 
 1907. 
 
 1/wt 
 
 Ms 
 
 ry 
 
 y^ 
 
 Wf 
 
 JULY 
 
 /wevsr 
 
 -sffn 
 
 ~flfffA 
 
 0C71 
 
 ^se/f 
 
 *w. 
 
 1907 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 = p- 
 
 S 
 
 L > 
 
 
 
 950 
 
 
 
 
 
 
 
 
 
 
 = 
 
 
 
 
 
 
 
 
 900 
 
 
 
 
 
 
 
 
 
 3 
 
 
 
 
 
 
 
 
 850 
 
 
 
 
 ^*v 
 
 
 
 7 -< 
 
 ***^ 
 
 P 
 
 
 
 
 
 
 
 
 800 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 FIG. 24. Curve of weight of cow No. 35. 
 
 from May 14 until May 31. From June 1 until June 15 daily doses of 
 three-twentieths grain strychnin were given. On June 16 she was 
 put in the loco-free pasture and the treatment was stopped. Her 
 weight at the beginning of the season was 440 pounds. At the time 
 treatment was discontinued she weighed 530 pounds and gained 
 
 1 
 
 650 
 600 
 550 
 500 
 450 
 
 1907 *&?/ 
 
 MJY 
 
 JUNE 
 
 JULY 
 
 Jt/evsr 
 
 sffrfftffff/f 
 
 OCT. 1907 
 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 jjj 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 -/ 
 
 / 
 
 
 < 
 
 
 
 
 
 
 
 
 
 
 
 \=^= 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 * 
 
 
 
 
 
 
 
 
 
 
 
 
 J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 := 
 
 r ^ 
 
 f^^* 
 
 
 
 
 
 
 
 
 
 
 
 
 _ ; sr/rYCb#//vf \ 
 
 
 
 
 
 
 
 
 
 
 Kio. '>. Curve of weight of lifift-r No. 64H. 
 
 continually from that time on (see text fig. -5). She was kept in 
 the loco-free pasture until the middle of September, when she 
 weighed 702 J pounds. The gain of this animal was very marked and 
 the change from a poor, worthless animal in the spring into an animal 
 fit for beef in midsummer was very noticeable. 
 
 No. 5")ti was a steer received from Mr. Moshei, of Hugo. It was 
 one of the wild locoes and very difficult to drive. It was extremely
 
 86 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 excitable when first brought to the station. Its coat was rough and 
 the animal was quite thin. We commenced by giving this animal 
 three-twentieths grain strychnin doses, but this was continued for 
 only four days, after which it was treated with one-half gram sodium 
 cacodylate, given hypodermically. This treatment was continued 
 from July 14 to August 23. When treatment commenced, the steer 
 weighed 717^ pounds. At the time treatment was discontinued its 
 weight was 810 pounds. It was kept until the middle of October, at 
 which time it weighed 925 pounds. 
 
 Strychnin. Fourteen head of cattle in 1907 were treated with 
 strychnin. Of these, Nos. 503, 559, 561, and 566 died. No. 559, 
 when received, was very poor and weak, and lived a comparatively 
 short time. No. 566 was so weak that a few days after it was received 
 it fell near a creek with its nose under water and was drowned. No. 
 561 had a complication of troubles that led to its death, although the 
 treatment with strychnin was evidently beneficial. It gained in 
 weight and apparently was doing better, but died, as the autopsy 
 showed, of pericarditis. 
 
 Nine of the animals treated were distinct cures. Of these, No. 38 
 had been kept in the loco pasture during the months of October and 
 November in 1906, but without showing any effect of loco poisoning. 
 In 1907 it was herded on AragaUus lamberti from the beginning of the 
 season until July 1, when it was taken in for treatment. For some 
 little time before this it had been showing distinct loco symptoms, 
 carrying its head low, and being slow in its movements. It showed 
 more or less lack of muscular coordination in its limbs. A few days 
 before this, on June 27, it had broken a horn and it became necessary 
 to cut it off. It lost considerable blood in this operation, and this may 
 have somewhat increased its inactivity. It was given four-twentieths 
 grain of strychnin for five days, when the dose was reduced to three- 
 twentieths grain. This was continued until July 31. During this 
 time it became extremely weak so weak that it could not be driven 
 to the stock yards for weighing, or even taken out into the good pas- 
 ture, but was kept near the house in the horse pasture. It began to 
 pick up in about a couple of weeks, and on July 24 was taken out into 
 the loco-free pasture with the other animals. Its weight on July 26 
 was 700 pounds. From July 31 it was given four-twentieths grain 
 of strychnin daily, and this was continued until August 23, when it 
 weighed 760 pounds. It was kept in the loco-free pasture during 
 the remainder of the season and on November 1 weighed 875 pounds. 
 It was then considered as entirely cured. The curve of weight is 
 shown in text figure 26. 
 
 No. 547 was a heifer received from Mr. Woods, of Hugo. It was 
 brought to the station April 22. It was a yearling heifer, very thin 
 and wild eyed, and dragged its hind legs when walking, in the typical
 
 TREATMENT OF CATTLE IN 1907. 
 
 87 
 
 loco fashion, and it was noticed that it ate with the stiff motion of the 
 jaws which is peculiar to locoes. The animal was treated by admin- 
 istering three-twentieths grain strychnin hypodermically daily until 
 May 14, when the dose was increased to four-twentieths grain. This 
 treatment was continued until May 25. Besides the treatment with 
 
 850 
 800 
 750 
 700 
 
 1907 M/fY 
 
 JVA/ 
 
 JULY 
 
 /W6UST 
 
 SfPKMffZfi 
 
 OCX 1907 
 
 
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 ^^ 
 
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 V 
 
 
 
 
 
 
 
 
 
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 mew 
 
 V/H- 
 
 
 
 
 
 
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 Atrsfn) 
 
 9 
 
 
 
 
 
 
 
 
 FIG. 26. Curve of weight of steer No. 38. 
 
 strychnin the heifer was given several doses of Epsom salts in order 
 to insure free movement of the bowels. From April 25 she was kept 
 in the loco-free pasture until the latter part of the season. When 
 received, she weighed 465 pounds; on May 24, when treatment was 
 
 
 
 1907, 
 
 1/Vf/L 
 
 M 
 
 UY 
 
 Jl> 
 
 we 
 
 jb 
 
 '/y 
 
 *(/6t. 
 
 /sr 
 
 Sff>r. 
 
 1907 
 
 700 
 650 
 600 
 550 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 f 
 
 
 
 
 
 
 
 
 
 
 
 j 
 
 
 
 
 
 
 
 
 
 
 
 
 f 
 
 
 
 
 
 
 
 
 
 
 
 
 s 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 ^-^^" 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
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 ^<r 
 
 ^^ 
 
 
 
 
 
 
 
 
 500 
 
 
 ? 
 
 ^ 
 
 
 
 
 
 
 
 
 
 
 
 >>T 
 
 ffYCH* 
 
 
 
 
 
 
 
 
 
 
 
 ^Sf 
 
 
 
 
 
 
 
 
 
 
 FIG. 27. ('iin-e of weight of heifer No. 547. 
 
 discontinued, her weight was 510 pounds, and it continued to increase 
 until the middle of vSeptemlx'r, when she weighed 712J pounds. 
 
 Plate XI, figures 1 and 2, show the animal's condition on April 23 
 and August 22. On June 4 the heifer was practically a cured animal 
 and was in thoroughly good shape, while at the date of the last pic- 
 ture, August 22, she was in condition fit for market. The curve (fig. 
 27) shows the increase in weight.
 
 88 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 No. 555 was a steer received from Mr. Mosher, of Hugo, on July 9. 
 It was weak, with rough coat, in poor flesh, and quite wild. Treatment 
 was commenced on July 10 with three-twentieths of a grain strychnin 
 daily and continued until August 23. During this time it had gained 
 60 pounds. Subsequently it was kept in the loco-free pasture until it 
 was returned to the owner about the middle of October. At that 
 time it weighed 750 pounds and was considered a complete cure. 
 The curve (fig. 28) shows its increase in weight. 
 
 Two other cattle were treated with strychnin. One of them, No. 
 68, was treated for too short a time to show any marked effects, 
 although it was noticed that there was some improvement. The other 
 one, No. 569, showed improvement, but had other troubles which 
 prevented a complete cure. 
 
 1 
 
 750 
 
 700 
 650 
 600 
 
 1907 J(/iY 
 
 AUGUST 
 
 OCT. 1907 
 
 FIG. 28. Curve of weight of steer No. 555. 
 TREATMENT OF HORSES IN 1907. 
 
 During the season of 1907 seven horses and one mule were treated. 
 Strychnin was used in only one case, and in this case not only the 
 strychnin was used, but also sodium cacodylate. It is difficult to tell 
 just what the effect of either of these substances was upon the horse 
 treated (No. 22). It gained during the season, but gained somewhat 
 slowly and could not be considered as a cure. 
 
 The other seven animals were treated with Fowler's solution alone. 
 Of these, two were distinct cures, and the others with one exception 
 all made gains. The exception was the mule. This was an old 
 
 Q No. 22 was pastured during the season of 1908 with no further treatment and 
 became a healthy, handsome animal.
 
 BUL. 112. BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. 
 
 PLATE XI. 
 
 Case 547, April 23, 1907. A heifer in an advanced 
 stage of loco poisoning. 
 
 Case 547, August 22, 1907. Completely recovered 
 under treatment. Heifer was sold for fat 
 beef. 
 
 Case 551, June 14, 1907. A horse in advanced 
 stages of loco poisoning; weight 510 pounds. 
 
 Case 551, September 20, 1907. After course of 
 treatment ; weight 825 pounds. 
 
 Case 71, June 10, 1907. A locoed sheep, emaciated 
 and extremely nervoui. 
 
 Case 71, September 22, 1907. Recovered, as a 
 result of course of treatment.
 
 TREATMENT OF HORSES IN 1907. 
 
 89 
 
 animal, a chronic loco, and its death was due not only to the effect of 
 the loco poisoning, but doubtless to old age. The history of two of 
 the animals treated is of special interest and is given below. 
 
 No. 551, belonging to Mr. Mosher, of Hugo, was received May 21. 
 It had been locoed the previous season and had been fed on grain all 
 through the winter. Plate XI, figure 3, shows its general appearance 
 on June 14. It was a miserable animal was very poor, its winter coat 
 was still on in spots, and gave it an especially woe-begone appearance. 
 It stood about in a listless way, with its head down, but when dis- 
 turbed, as by a sudden noise, it would jump and rear up, showing the 
 unstrung condition of its nervous system. It was 4 years old and 
 weighed 525 pounds. The case seemed almost hopeless and hardly 
 worth experimenting with. It was put on daily doses of Fowler's solu- 
 
 800 
 750 
 700 
 650 
 600 
 550 
 
 1907 M/lY 
 
 JL/A/f 
 
 JULY 
 
 OCr. 1907 
 
 FlQ. 29. Curve of weight of horse No. 531. 
 
 tion and given some chop and oil meal daily in addition to its pasture 
 feed. It gained rapidly. Figure 4, Plate XI, shows its appearance 
 on September 20. The treatment was continued thirty-three days, 
 but the animal was kept in the pasture through most of the season. 
 In the fall it weighed 810 pounds and was a fine, sleek-looking 
 horse. The curve (fig. 29) shows its increase in weight as the result 
 of treatment. 
 
 No. 504 was a gelding belonging to Mr. Norlhnip, of Hugo. Tie 
 was 7 years old, had boon used as a work horse, and had boon consid- 
 ered a gentle and valuable animal. Within two works preceding the 
 timo that he was brought to the station he had developed peculiar 
 nervous symptoms would throw himself, kick, and bohavo in a very 
 erratic manner generally, so that it was considered unsafe to use him 
 longer as a work horse. He was put on daily doses of Fowler's solu-
 
 90 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 tion and fed a little chop each day. The treatment was continued 
 for twenty-eight days, when he was taken by the owner and again 
 put tq work. He gave no further trouble and was later sold as a 
 sound horse. 
 
 Of the others, No. 572 was treated for so short a time that it was 
 impossible to say whether very much benefit was received from the 
 treatment. It was a horse belonging to Mr. Dayton, was at the 
 ranch only ten days, and it was difficult to say when it was discharged 
 whether it had really made very much gain or not. 
 
 One horse was treated at Woodland Park. This animal was con- 
 fined in a corral and fed chiefly upon old hay. Fowler's solution was 
 administered in its drinking water. The horse was not under constant 
 observation, as were the animals in Hugo, but it made steady gain 
 under the treatment. 
 
 TREATMENT OF SHEEP IN 1907. 
 
 One sheep was treated in 1907. This was brought by Mr. Frank 
 Hamp, and while the history of its feeding previous to the time when 
 it was brought to the station was not known, it was pronounced by 
 Mr. Hamp, an experienced sheepman, as a good case of loco poisoning. 
 It was received June 10. It was in fair flesh, but in a highly nervous 
 state. Its head was held high and shook with a peculiar vertical motion 
 so that its teeth rattled together. It certainly deserved the name of 
 crazy. It was put on one-twentieth grain doses of strychnin and 
 showed marked improvement in less than two weeks. The treat- 
 ment was continued for thirty-three days, when the nervous symp- 
 toms had disappeared, and it appeared all right in every way. This 
 animal seemed to be a perfect cure. Plate XI, figures 5 and 6, show 
 its condition when received, June 10, and when it was considered a 
 cure, September 22. 
 
 A number of sheep that were left at the station by Mr. Mclntyre 
 and were considered locoes were kept during the season, but it was 
 decided that none of them were cases of loco. They showed no tend- 
 ency to eat the plant, would eat grass simply, and it was decided that 
 the poor condition of the animals when received was largely the result 
 of the presence of animal parasites. Some of them were treated for 
 (Estrus ovis, and all came out in the fall in good condition without 
 any further treatment.
 
 PART III. RESULTS AND CONCLUSIONS. 
 CAUSE OF THE DISEASE. 
 
 The first and most important question arising was to decide 
 whether the disease was caused by the loco plants. While the results 
 of previous investigation cast much doubt on their poisonous charac- 
 ter, the great majority of the stockmen were agreed that the loco 
 plants were at the bottom of the trouble. Great interest, therefore, 
 was attached to the feeding experiments. At first it appeared that it 
 would be shown that they were harmless. The animals placed in the 
 loco pasture not only did not suffer from any harmful effects of the 
 weed, but, on the other hand, grew sleek and fat. The horses fed in 
 the corrals showed no unusual symptoms. This went on for some 
 weeks. When the effects of the poison began to show themselves 
 they came very suddenly, and within a short time the animals suc- 
 cumbed entirely. The conditions in the feeding experiments were 
 such that the deaths of these animals must have been caused by loco. 
 As compared with animals under conditions in other respects iden- 
 tical, the loco eaters invariably grew poor and eventually died. In 
 the cases where loco was fed exclusively it may of course be said 
 that the trouble was a lack of nutrition in the plant. This possibly 
 might have been the case in some of the horses of the first season, but 
 in the other cases an abundance of other feed was provided and in 
 spite of that the animals went down. 
 
 During the second season a careful record of weights was kept and 
 curves made to show the changes during the season. The curves 
 show in a striking way the fact that loss of weight always followed 
 the feeding of loco. All the horses, cattle, and sheep that ate loco 
 in any amount were affected. No. 10 was especially interesting, 
 because, although he ate loco, he did it in moderation, so that he 
 lived in a comparatively fair condition, but with less than the normal 
 increment in weight. 
 
 During the third season, too, the curves of weight showed some 
 loss whenever any considerable amount of loco was eaten. In the 
 summer of 1907 there was no forced feeding of loco, but the animals 
 experimented upon were kept constantly where loco was abundant, 
 and a daily record was kept of what was oaten by the animals when 
 they were in the field. It was noticed that the weights varied 
 much, according to the amount of loco eaten. No. 10 kept on in the
 
 92 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 third summer as he had before, with the same general result, being 
 a rather poor specimen of a steer, but not suffering largely from his 
 bad habit. 
 
 Of the previously suggested causes of the disease other than the 
 plants themselves, most had no reasonable basis and no discussion 
 of them is necessary. The theory of animal parasites, however, 
 did have a definite experimental basis. It was noticed in the begin- 
 ning of our work on horses and cattle that not only was there no 
 unusual number of parasites present in the subjects, but in many 
 cases the number was unexpectedly small. The horses had bots, 
 as .do nearly all horses, but the number of intestinal worms was 
 remarkably small. In many of the cattle no parasites at all were 
 discovered. Examination of the blood gave no evidence of blood 
 parasites. 
 
 With the sheep, however, it was a different matter. The general 
 presence of (Estrus ovis and Thysanosoma actinioides was very notice- 
 able. Inasmuch as the symptoms produced by (Estrus ovis some- 
 times resemble closely those of loco, a skeptical person might well 
 question the fact of loco poisoning. Sheep, too, are erratic about 
 their feeding, and in many cases it is a matter of some difficulty to 
 get exact evidence of any considerable feeding upon the weed. If 
 we not had our experience with horses and cattle before experiment- 
 ing with sheep, it is very likely that we should have considered 
 Marshall's conclusions as confirmed by our observations. But having 
 already acquired positive evidence in regard to other animals, we 
 were not as likely to be skeptical in regard to sheep. After some 
 experience we could, by post-mortem examination, distinguish locoes 
 readily, but it is very difficult before death to tell a locoed sheep from 
 one suffering from grub in the head. 
 
 SYMPTOMS OF LOCO POISONING. 
 
 The field work has added very little new material to what had 
 already been published in regard to the symptoms of loco disease. It 
 appears that in some cases authors had exaggerated these symptoms 
 and many of the recorded symptoms can not be verified, but in gen- 
 eral they were correct. 
 
 During the early period of loco feeding there are no symptoms of 
 poisoning. Horses and cattle will eat quite freely of the weed for a 
 considerable period with no apparent ill effects and may even gain 
 considerably in flesh. 
 
 The first symptoms of loco poisoning in hor33s are in the gait. 
 The animal walks with a peculiarly stiff motion. It staggers as it 
 walks, frequently moving the hind limbs with a noticeable drag, as 
 though they were partially paralyzed. Its hind legs may be kept
 
 SYMPTOMS OF LOCO POISONING. 93 
 
 far apart, as if in an attempt to support itself. In stepping over an 
 obstacle it lifts its feet unusually high with a jerking motion, and may 
 leap unnecessarily high, as though unable to judge of distance. It 
 may stumble and fall, getting up with a good deal of difficulty. The 
 animal develops a solitary habit, staying away from the rest of the 
 bunch. This solitary habit is supposed by some to be due to its desire 
 to hunt loco, but is probably simply because of its general nervous 
 depression. These symptoms may appear when the animal is in 
 fairly good flesh. It becomes slow and "dopy." It may stand for 
 hours without eating and not go to water for days. When it attempts 
 to drink it may have difficulty in getting its head to the water, and, 
 when it reaches it, may move its mouth as though attempting to eat 
 rather than with the motions of drinking. This peculiarity in drink- 
 ing is accompanied by equally peculiar motions in eating and may 
 be very pronounced before the animal deteriorates much in flesh, as 
 shown in Plate V, figure 1. 
 
 The animal may eat little but loco, going from plant to plant hunt- 
 ing the weed. More commonly it eats considerable grass with the 
 weed, but as the disease progresses it eats less and less of anything. 
 
 Sometimes a horse in the earty stages of the disease will be in con- 
 stant motion, walking about in a restless and aimless sort of way. 
 If such a horse is confined in a corral, it may walk around the corral 
 constantly, apparently never resting. As the effect of the loco 
 increases, the animal loses flesh, its coat becomes rough, and its eyes 
 staring. A horse in this condition will stand hour after hour the 
 very picture of dejection, showing no interest in anything. If ap- 
 proached suddenly it will rear, its legs flying about in a peculiarly 
 purposeless way, and perhaps fall over backward. This is well shown 
 in Plate V, figures 2, 3, and 4. 
 
 A locoed horse when driven may shy violently at some little thing, 
 and it is dangerous to use such an animal. A horse that becomes 
 locoed after being broken may become entirely unmanageable. It is 
 impossible to lead it, back it, or tie it. Generally speaking, however, 
 the crazy symptoms are not so noticeable as would bo supposed from 
 the popular accounts. Nearly all locoed animals, when much affected, 
 are constipated. 
 
 Cattle show the same symptoms, but none in so marked a way. A 
 steer will not rear, but a sudden noise will send a tremor through its 
 whole body, and in walking it shows the same lack of muscular coor- 
 dination that is seen in the horse. From the fact that one can ap- 
 proach close to one of these animals without being noticed, and that 
 then the animals will suddenly rear and jump, it is popularly thought 
 that the eyesight is affected. It does not appear, however, that there 
 is really any defective vision, but that the apparent trouble with the
 
 94 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 eyes is simply due to the general disorganized condition of the ner- 
 vous system. Probably the trouble is mental rather than due to 
 any difficulty with the eyes, although this is a difficult matter to 
 decide positively. It is sometimes difficult to lead a locoed animal 
 into a barn, as it is apparently afraid that the door is not high enough, 
 or it may crouch as if to avoid something that is not present at all. 
 This is well shown in Plate VII, figures 1 and 2, where the animals in 
 going through a gate crouch and avoid an imaginary wire or an upper 
 bar. 
 
 Commonly, a locoed animal is dull, but under especially exciting 
 causes it may become almost frantic. This is particularly noticeable 
 in steers taken off the range, which will sometimes go into paroxysms 
 of rage and attack everything in sight. It is almost impossible to drive 
 a locoed animal. It may run into the horse of the person driving it. 
 When started in one direction it is sometimes almost impossible to 
 turn it. Sometimes an animal after being started will go straight 
 ahead at a uniform gait until it strikes some obstacle. If this ob- 
 stacle happens to be a wire fence it will go through it, paying no atten- 
 tion to incidental cuts. This would not be so surprising in the case 
 of a steer, for cattle under normal conditions will frequently go through 
 a fence with little harm, but most horses are afraid of barbed- wire, 
 and even a small cut will stop them. Not so with locoed horses; 
 they will sometimes rub along a fence, mangling themselves, but ap- 
 parently suffering no pain. The condition of such a horse is shown 
 in Plate VIII, figure 6. It is evident that the nerves of sensation are 
 partially paralyzed. It is noticeable, too, that a horse that has been 
 cured of loco has permanently lost much of its sensitiveness. The 
 whip and spur sometimes make very little impression, although the 
 animal may have been very sensitive before suffering from the loco 
 poison. 
 
 In general, the symptoms in horses and cattle are very much the 
 same. The lack of muscular coordination is more noticeable in horses, 
 as would be expected from their more delicate nervous organization. 
 The head of a locoed steer or cow will shake like the hand of a palsied 
 man. Frequently in cattle there will be local accumulations of serum, 
 especially under the jaw. These are not so likely to occur in horses. 
 Abortion is a common phenomenon in locoed cows. By many 
 stockmen this loss of the calf crop is sometimes considered one of the 
 most serious of the effects of loco. As the disease progresses, the 
 animals eat less and less and finally die of starvation. 
 
 Another symptom which was noticed in some of the cattle was a 
 tetanic condition of some of the flexor muscles of the hind limb, so 
 that the fetlock joint was flexed and the animal appeared to be 
 "standing on its toes." This is shown in Plate X, figure 5.
 
 PATHOLOGICAL LESIONS. 95 
 
 The symptoms in sheep are similar to those in horses and cattle, 
 but, as would be expected from the character of the animals, they 
 are less noticeable. The locoed sheep walks in a stiff way, staggers, 
 and becomes weak. It lies down frequently and does not keep up 
 with the band. Its head may shake, although this is not a very com- 
 mon phenomenon. The herders say that locoed sheep are "foolish" 
 or "crazy," and these terms describe very well the general appear- 
 ance of the animals. Lambs are pecu iarly susceptible to the influ- 
 ence of the poison and may succumb to it within two or three weeks, 
 dying with very little loss of flesh. 
 
 It will be remembered that in the list of symptoms both high and 
 low temperatures were mentioned. The results of the field work would 
 seem to indicate that both classes of observers were right. In some 
 locoed animals temperatures as high as 106 or 108 F. have -been 
 observed, and in a few cases subnormal temperatures. In a great 
 majority of chronic loco cases, however, the temperature does not 
 differ much from the normal, and it can be safely said that chronic 
 loco poisoning does not have any distinct effect upon the body tem- 
 perature. 
 
 PATHOLOGICAL LESIONS. 
 
 Loco victims always show marked anemia. This is indicated not 
 only by the emaciation and paleness of the flesh, but by the excess of 
 serous fluids of the body and by the deposits of organized serum in 
 various parts of the body. This is more especially marked at the 
 base of the ventricle of the heart. 
 
 EXAMINATION OF BLOOD. 
 
 Inasmuch as all locoed animals show marked symptoms of general 
 anemia, a technical study of the blood is of considerable interest. 
 The multiplicity of general duties at the station made it impossible 
 to make any very large number of blood determinations. Some counts, 
 however, were made in the second and third summers and the results 
 are significant. Little seems to have been published in regard to 
 the blood counts of cattle, and it would have been interesting if 
 we could have made a large number of counts of both normal and 
 locoed animals. The counts in the summer of 190(> were made by 
 Scientific Assistant Klugh, and his work was checked off by counts 
 made by two other assistants. In 1 ( .M)7 the blood counts were 
 made by Field Assistant Clawson, and this work was checked by 
 counts made by two others. 
 
 The normal number of reel corpuscles for cattle at our station 
 seemed to be something over 8,000, 000. This is higher than recorded 
 normals, but our station was at an altitude of nearly o.OOO feet, and
 
 96 
 
 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 we would expect higher counts at this elevation. The locoed animals 
 examined in 1906 averaged 5,138,333; those examined in 1907, 21 
 in number, averaged 7,250,238. This apparently shows a wide dis- 
 crepancy. It is largely explained, however, by the fact that those 
 examined in 1906 were nearly all in the last stages of the disease, 
 while most of those examined in 1907 were undergoing treatment 
 and in some cases had already made marked gains. These results 
 are such as would be expected, emphasizing the fact of the marked 
 anemia. The following table is significant as indicating the effect 
 of treatment upon locoes, as it shows in general gradual improvement 
 as the course of treatment progressed. 
 
 Number of red corpuscles in blood of number of normal and locoed cattle, the latter in 
 
 rarious stages of treatment. 
 
 Xo. of animal. 
 
 Treated 
 less than 1 
 week. 
 
 Treated 1 
 to 4 weeks. 
 
 Treated 4 
 weeks and 
 over. 
 
 Not 
 locoed. 
 
 Remarks. 
 
 36 
 
 6,180,000 
 
 
 
 
 IDied, bad 
 
 36 
 
 
 7 580 000 
 
 
 
 / jaw. 
 
 38 
 
 
 6,000,000 
 
 
 
 Bad case. 
 
 43 ... 
 
 
 
 
 8,000,000 
 
 
 546 
 
 
 
 6,650,000 
 
 
 
 546 
 
 
 
 9 600 000 
 
 
 
 546 
 
 
 
 8,840.000 
 
 
 
 554 
 
 
 9,917,000 
 
 
 
 
 556 
 
 
 5,380,000 
 
 
 
 
 556 
 
 
 8,900 000 
 
 
 
 
 560 
 
 5,930,000 
 
 
 
 
 Died. 
 
 42 . 
 
 
 6, 979, 000 
 
 
 
 
 361 
 
 7,508,000 
 
 
 
 
 
 557 
 
 
 
 8,520,000 
 
 
 
 558 
 
 
 6,120,000 
 
 
 
 
 566 
 
 6,810,000 
 
 
 
 
 
 569 
 
 6 070 000 
 
 
 
 
 
 557 
 
 
 
 8 220 000 
 
 
 
 35. 
 
 
 
 6.473.000 
 
 
 
 
 
 
 
 
 
 Average 
 
 6,511 600 
 
 7 268 000 
 
 8 050 000 
 
 8,000,000 
 
 
 
 
 
 
 
 
 An average of 12 locoes in 1907 showed 3,735 white corpuscles. 
 
 Tests of hemoglobin were made by the Talquist scale. Healthy 
 animals varied from 85 to 98, the average being between 90 and 95. 
 In the locoes examined in 1906 the hemoglobin was 70, while in 1907 
 it averaged 85. The lowest observed in 1907 was 75 and the highest 
 85. It should be borne in mind, however, that many of the 1907 
 locoes were on the road to recovery, and in some cases were in very 
 good condition. 
 
 On July 21, 1906, 10 healthy sheep were taken at random from a 
 herd that were in the shearing sheds, and an examination of hemoglo- 
 bin made by the Talquist method. The average of these 10 gave 
 87.7. On the same date an examination was made of 14 locoed 
 sheep, giving an average of 78.
 
 PATHOLOGICAL LESIONS. 97 
 
 WALLS OF STOMACH. 
 
 In nearly all locoes there is a diseased condition of the stomach. In 
 acute cases the walls are very much inflamed. In chronic cases ulcers 
 are commonly present. The ulcers are not so common in the stom- 
 achs of horses, but are almost invariably present in the fourth 
 stomachs of cattle. In sheep one is apt to find inflamed walls rather 
 than ulcers. 
 
 In these ulcers a microscopic examination shows that the mucous 
 membrance is entirely destroyed. Sometimes other parts of the 
 alimentary canal may be inflamed, or have small ulcers, but this is not 
 a usual condition. 
 
 HEMOLYMPH GLANDS. 
 
 The hemolymph glands are apparently much more prominent in 
 locoes than in normal animals. This is especially noticeable in cattle. 
 In these animals the hemolymph glands seem to be very numerous in 
 the thoracic cavities, in the connective tissue about the heart, and in 
 that in front of the thoracic aorta. They are only less noticeable in 
 the lumbar region of the abdominal cavity. In the literature on the 
 hemolymph glands there seems to be nothing in regard to the 
 question as to whether numbers of these glands have any pathological 
 significance. Most of the investigations have been directed to 
 physiological questions. There has been no opportunity for the 
 author to make the extended observations which would be necessary 
 to throw light on this question. Preliminary observations on a con- 
 siderable number of animals in slaughterhouses make it seem 
 probable, however, that the normal number is much smaller than in 
 the case of locoes, and it seems possible that the condition of chronic 
 anemia in these poisoned animals may be correlated with the number 
 of hemolymph glands. 
 
 NERVOUS SYSTEM. 
 
 The central nervous system is generally in a hyperemic or con- 
 gested condition. In a few cases clots were found in the lateral 
 ventricles of the brain. We have never, however, found clots in the 
 fourth ventricle, although this has repeatedly been said to have been 
 the case by the earlier observers of loco phenomena. 
 
 The serous exudate in the epidural space is especially abundant 
 
 and is more or less organized. Commonly it is particularly abundant 
 
 about the points of exit of the spinal nerves. This condition is rarely 
 
 absent in chronic locoes. It seems probable that the pressure of this 
 
 79154 Bull. 11209 7
 
 98 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 coagulated serum may be the cause of many of the nervous symptoms 
 which are pronounced in loco victims. In some cases this coagulated 
 serum is especially abundant in the lumbar region, and it might well 
 be the cause of the partial paralysis of the hind limbs, which is fre- 
 quently very marked. 
 
 In locoed cows and mares, generally speaking, the ovaries are found 
 to be more or less diseased. They are generally small and hard, and 
 frequently contain serous cysts. 
 
 In a number of cases it was found that the kidneys were somewhat 
 diseased. This was not, however, the condition of the majority of 
 the cases, and would not seem to be typical of loco poisoning. 
 
 VIRULENCE OF LOCO POISON. 
 TIME REQUIRED TO PRODUCE POISONING. 
 
 Previous authors vary greatly in regard to the length of time taken 
 for loco to affect animals. Some say that it takes only a few days; 
 others that the poison may be several years in producing marked 
 effects. Our work seems to show that small amounts of the weed 
 produce no appreciable effect, and that the poison is cumulative, so 
 that the apparent results come quite suddenly after a period when the 
 animal does not appear to be affected at all. The time from the 
 beginning of the feeding to death in the animals experimented upon 
 varied from two months and eight days to six months and nine days. 
 It might be expected that there would be much variation in the time, 
 because it is impossible to secure uniformity in conditions. There 
 is a great difference in the individual susceptibility to the poison, and 
 when animals are in the pasture some eat a very much larger amount 
 of the loco than do others. When fed in the corral, too, on a mixture 
 of loco and other feed, there will be an individual difference in the 
 relative amount of loco eaten. Of the 1905 cattle dying of loco, the 
 average length of life after the feeding was begun was five months 
 and six days. Of these, No. 12, which was fed partly in the corral, 
 died in three months and thirteen days. Of the other four, two died 
 in six months and five days, and one in six months and four days. 
 This would seem to indicate that the corral-fed animals succumbed 
 the more quickly. In this, as in other cases, we must bear in mind, 
 however, that while doubtless the corral-fed animals ate more loco, 
 they may also have suffered somewhat from confinement and from 
 an actual lack of proper food. This doubtless was true in the case of 
 
 o Dr. John R. Mohler, chief of the Pathological Division of the Bureau of Animal 
 Industry, calls attention to the fact that a cystic condition of the ovaries is a com- 
 mon condition in the horses and cattle of the West, and that this condition may not 
 be due to the specific effect of the loco poison.
 
 VIRULENCE OF LOCO POISONING. 99 
 
 some of the animals of the first year. Then, too, generally speaking, 
 when animals were first taken into the corral they were starved to 
 give them an appetite for loco. In other cases some were fed loco 
 exclusively for many days. This treatment doubtless would occasion 
 considerable losses. 
 
 Of the 1905 horses the average length of life after commencing to 
 eat loco was three months and seventeen days ; those eating Aragallus 
 lamberti lived three months and nineteen days ; those eating Astraga- 
 lus mollissimus lived two months and ten days. 
 
 In 1906 cattle lived on the average three months and seventeen 
 days ; the corral-fed lived three months and four days ; the pasture- 
 fed lived three months and seventeen days. The horses lived four 
 months and nineteen days ; the horses eating Aragallus lamberti lived 
 four months and twenty-four days ; those eating Astragalus mollissi- 
 mus lived three months and fourteen days. Those in the Aragallus 
 lamberti pasture lived four months and twenty-eight days; those fed 
 on Aragallus lamberti in corral lived four months and twelve days. 
 
 It will thus be seen that in the first year the horses died sooner 
 than the cattle, while in the second year the cattle lived the shorter 
 time. This difference in results I will not attempt to explain fully. 
 It may be said, however, that in the season of 1905 more of the 
 horses than of the cattle were fed in the corral, and doubtless they 
 suffered more from shortness of feed, especially as some of them were 
 for a time fed on loco exclusively. In the season of 1906 one of the 
 cattle had eaten loco during the latter part of the preceding season, 
 but this time was not taken into account in the tabulation of the 
 averages. This reduced the average of the cattle somewhat. Then 
 there is reason to think that some of the second season's cattle were 
 peculiarly susceptible to the poison. The cattle during the second 
 season ate much more freely of the weed than did the horses. It 
 must be recognized that the number of our cases is not large enough 
 so that we can place implicit reliance on averages. All we can say 
 is that the results are significant, but must be interpreted very 
 carefully. 
 
 The animals eating Astragalus mollissimus died more quickly than 
 those eating Aragallus lamberti. Of the horses of 1905, those eating 
 Aragallus lamberti died in three months and nineteen days; those 
 eating Astragalus mollissimus in two months and ten days. Of the 
 horses of 1906, the one that was fed Astragalus mollisxinivs died in 
 three months and fourteen days, while those eating Aragalhis lamberti 
 died in four months and twenty-four days. 
 
 The work upon sheep was of such a character that no general con- 
 clusions can be drawn as to the length of time for the poison to take 
 effect.
 
 100 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 Horses and cattle feeding freely and continuously upon AragaUus 
 lamberti may live from three to six months. Horses feeding freely 
 and continuously upon Astragalus mollissimus are not likely to sur- 
 vive longer than from two to four months. The fatal issue of the 
 habit may be put off almost indefinitely, however, in the case of the 
 moderate eater. It may live a year or several years, but it greatly 
 deteriorates. 
 
 During the third season none of the animals were fed in the corral, 
 but all were kept in a pasture where they had an abundance of grass, 
 and they were not forced upon the loco except that they were held a 
 part of the time where loco was abundant. As soon as they showed 
 evident symptoms of being poisoned they were taken up for treatment 
 instead of being permitted to go through the whole course of the loco 
 disease, as in preceding seasons. An attempt was made to preserve 
 life as long as possible and to produce cures when practicable. The 
 natural result of these conditions was that the animals yielded to the 
 poison much more slowly than in the preceding season. Another 
 fact had, doubtless, some influence, namely, that the animals were 
 in most cases the survivors of preceding experiments and were origi- 
 nally more or less immune to the effects of the loco. 
 
 AMOUNT OF LOCO NECESSARY TO PRODUCE POISONING. 
 
 The limitations of the field work and the comparatively small num- 
 ber of animals experimented upon make it impossible to state with any 
 definiteness how much loco an animal must eat before showing symp- 
 toms of the poison. In all cases some pasture feeding was given to the 
 animals kept in the corrals in order to give them suitably healthful 
 conditions of life. When in the pasture, some would eat loco in con- 
 siderable abundance, while others would devote themselves wholly 
 or in a very large part to grass. It was our custom to put these ani- 
 mals into pasture at least one day in the week. It is to be presumed, 
 too, that the amount of hay eaten while they were in the corrals 
 would make some difference in the effect of the poison, and thus bring 
 hi wide individual variations. 
 
 Because of the small number of animals it was possible to subject 
 only a few to a single line of treatment. In most cases each animal 
 was a subject of several phases of the experiment. The amount of 
 loco fed in the corrals, however, was weighed and a record kept for 
 each animal. From these records we can make a rough estimate of 
 the amount eaten before the symptoms of loco became evident. 
 From these records it appears that about 400 pounds of AragaUus 
 lamberti will loco the average horse or steer.
 
 RELATIVE IMPORTANCE OP SPECIES INVESTIGATED. 101 
 
 RELATIVE IMPORTANCE OF ASTRAGALUS MOLLISSIMUS AND 
 ARAGALLUS LAMBERTI. 
 
 The tentative conclusions reached at the end of the first year in 
 regard to the effects of Aragallus lamberti and Astragalus moUissimus 
 were amply confirmed by the work of the second and third years. 
 Astragalus moUissimus is harmful only to horses. The loss of cattle 
 from this plant is inconsiderable. This is not because the cattle can 
 not be affected by the poison, but because they do not eat the weed. 
 It was found in the corral experiments almost impossible to make 
 cattle eat this species even when they were starved to it. Generally 
 they would starve to death rather than take to it. So far as our 
 experiments went, it may be said that cattle never eat Astragalus 
 moUissimus. In regions where this weed prevails, and not Aragallus 
 lamberti, locoed cattle are almost unknown. Examples of this are 
 the regions about Holyoke, Colo., and Imperial, Nebr. The same 
 thing is reported in the Astragalus moUissimus region in the Pan- 
 handle of Texas. About Santa Rosa, N. Mex., where the damage is 
 commonly ascribed to Astragalus moUissimus, it is true, the author 
 was told that possibly 10 per cent of the cattle and 50 per cent of the 
 horses were lost annually. It would appear that perhaps Astragalus 
 moUissimus was responsible for the loss of the cattle in this locality. 
 The locoes of this neighborhood, however, have not been examined 
 with any care, and it is possible that plants other than Astragalus 
 moUissimus are responsible for the cattle loss. Our experience 
 showed that not only would the cattle not eat Astragalus moUissimus, 
 but that horses were not likely to take to it except because of scarcity 
 of other food. 
 
 It is very different with Aragallus lamberti; not only horses, but also 
 cattle and sheep, eat this readily. They are more likely to eat it 
 during a scarcity of other food, but they will not only continue to eat 
 it when other food is abundant, but may begin the habit at any time 
 of the year. Of course they are more likely to start eating the loco 
 in the winter and early spring and in the fall when the loco is green 
 and succulent and the grass is dry. But even in midsummer, when 
 supplied with abundant pasturage, if thrown in contact with loco 
 plants they may eat considerable amounts -enough, even, to produce 
 fatal results. Cattle eat Aragallus lamberti much more readily than 
 do horses. Nearly all cattle will eat it more or less, and a large pro- 
 portion will contract the habit. A great many horses, on the other 
 hand, will not touch it even if run upon ranges covered with the 
 weed. Consequently the loss of cattle from AmpaUux lamberti is 
 much greater than that of the horses. 
 
 Sheep, too, eat Aragallus lamberti very readily. It is always con- 
 sidered a misfortune to have a few sheep commence eating the weed,
 
 102 THE LOCO-WEED DISEASE OF THE PLAINS. 
 
 for sheep are such imitative creatures that a few may lead a whole 
 band astray. Some sheepmen immediately cut the throats of loco 
 eaters on this account. 
 
 The symptoms of poisoning from AragaUus lamberti are like those 
 from Astragalus mottissimus, but the effect does not come so quickly. 
 The laboratory work conducted by Doctor Crawford has established 
 the fact of the greater toxicity of Astragalus mollissimus. However, 
 vastly the greater amount of damage is done by AragaUus lamberti 
 because it is eaten so much more readily, and because it affects cattle 
 and sheep as well as horses. Our pasture experiments all go to show 
 that most horses when kept where AragaUus lamberti is abundant 
 will sooner or later yield to the poison, and that the cattle succumb 
 much more quickly to the attractions of the weed. 
 
 SUSCEPTIBILITY OF DIFFERENT BREEDS. 
 
 Sheepmen are unanimous in saying that the blackfaces are much 
 more susceptible than the Merinos. This statement was abundantly 
 confirmed by our observations. 
 
 In regard to cattle and horses, it is a matter of common observa- 
 tion among stockmen that the better bred animals are more likely 
 to become locoed. They explained this in part, and probably 
 reasonably, by the fact that animals accustomed to be taken care 
 of do not know how to " rustle, " and consequently take the food 
 that comes first instead of hunting for better material. Reliable 
 stockmen tell me that Durhams are more easily affected than Here- 
 fords. When our experiments started in Hugo, an old stockman 
 remarked that two black steers in our herd would be the first to be 
 affected, saying that this would be true not because of their color 
 but because they were of better blood. The result showed the 
 accuracy of his prophecy, for the black ones were the first to suc- 
 cumb. While we had a number of different breeds among our 
 experimental animals, the numbers were not large enough for any 
 general conclusions to be drawn. The experiments would indicate, 
 however, that Herefords are decidedly less susceptible than Aberdeen- 
 Angus cattle. The one steer of our herd that refused to eat any con- 
 siderable amount of the loco was a scrub. In Colorado generally I 
 saw more locoed Herefords than of any other breed, but this is 
 doubtless explained by the fact that this is the most popular breed 
 of range cattle. 
 
 AGE SUSCEPTIBILITY. 
 
 Marshall (1904) states that loco poisoning appears only in young 
 sheep, generally speaking; never in those over 2 years old. Blank- 
 inship (1903) states that only young sheep and colts are affected. 
 Older sheep and horses rarely acquire the habit. Our experiments
 
 EFFECT OF LOCO ON VARIOUS ANIMALS. 103 
 
 in Colorado show that while lambs suffer in an acute way from loco, 
 the older sheep are by no means free from the disease. 
 
 In cattle and horses we had a general impression of the greater 
 susceptibility of the younger ones, but this was hardly borne out by 
 the facts. There seemed to be very little difference in the time 
 taken to kill, whether the animals were young or old. We could 
 determine but little about this in the first season's work, for most of 
 the stock were young animals. During the second and third seasons, 
 however, we had a number of old animals, especially among the 
 horses, and there was no clear-cut difference in susceptibility to the 
 poison because of difference of age. As is intimated elsewhere, there 
 is a difference in individual susceptibility which must always be taken 
 into account. 
 
 The apparently greater susceptibility of young animals, as noticed 
 by other observers, may be due in part to the fact that there are 
 more young animals than older ones, and hence apparently a greater 
 number of cases among the young animals, and partly to the fact 
 that many of the old animals are those that have survived because 
 of an individual lack of susceptibility to the temptations of the plant. 
 
 EFFECT ON ANIMALS OTHER THAN HORSES, CATTLE, AND 
 
 SHEEP. 
 
 We found it very difficult to get evidence of the effect of loco on 
 mules. Some stockmen reported that they had seen locoed mules, 
 while others said that mules were not affected. Considerable interest, 
 therefore, attached to observations of the two mules which formed a 
 part of our experiment in 1906. Unfortunately, both were old ani- 
 mals, and the poorest one died of old age. The other, however, was 
 a fairly healthy animal and its death proved conclusively that mules 
 could be locoed. 
 
 In the summer of 1907 a locoed mule was brought in to the station 
 for treatment. It had the typical symptoms of loco poison. Its 
 insensibility to barbed-wire fence cuts was especially marked, for it 
 would run against a fence and rub itself along for two or three lengths, 
 the wire cutting through the skin and into the muscle, but apparently 
 occasioning no pain. When started up in the pasture it would trot 
 along at a slow gait in almost a straight line, going for a long distance, 
 sometimes until some obstruction in its way would stop it. This 
 was an old animal, and while it would eat fairly well and we found it 
 possible to dose it, it succumbed, probably from the combined influ- 
 ence of old age and the loco poison. There seems no longer any 
 question in regard to the possibility of mules becoming locoed by 
 eating AragaXLus lamberti. It does not appear, however, that they 
 are as liable to take to the plant as are horses.
 
 104 THE LOCO-WEED DISEASE OP THE PLAINS. 
 
 In regard to other domestic animals and wild animals, the testi- 
 mony is conflicting, and it is impossible now, with the evidence at 
 hand, to pass on it. Some stockmen say that they have seen locoed 
 antelopes. Others say that antelopes are not affected. Inasmuch, 
 however, as there is no record of feeding experiments on antelopes, 
 we must consider the matter as still an open question. Doctor Craw- 
 ford's pharmacological work shows that rabbits are affected, and it 
 must be presumed that other herbivorous animals may be susceptible 
 to the poison of the weed. One reputable stockman told me of a 
 man who fed cut loco to a lot of pigs, thinking it would be good for 
 them, and locoed them all. The writer has even heard of locoed 
 hens. 
 
 EFFECT ON MAN. 
 
 There are many stories of men poisoned from eating loco, but 
 none of these can be authenticated. As a matter of fact, inasmuch 
 as our work on horses, cattle, and sheep shows that the poison is 
 very slow in taking effect and that an animal can eat the weed for 
 quite a long time without any apparent harmful results, it seems 
 unlikely that men have eaten enough to show the results of the 
 poison. Pilgrim in 1898 investigated a case which was brought into 
 the Hudson River State Hospital, and concluded that the cause was 
 syphilis. The story by Janvier in Scribner's Magazine, Volume I, 
 page 67, entitled "In Mexico," which is frequently quoted in this 
 connection, was based on the properties not of the loco plant, but of 
 stramonium. 
 
 LOSSES FROM LOCO POISONING. 
 
 Attempts have been made to get some estimate of the losses from 
 loco poisoning, but it is impossible to make more than the rudest 
 kind of conjecture. An intelligent horseman . near Wray, Colo., 
 estimated in 1905 a loss of 3 per cent of the horses. One man near 
 Holyoke in 1906 lost from 12 to 20 per cent of the horses in one herd; 
 another in the same locality in 1905 lost practically all his horses. 
 The winter of 1906 was especially disastrous in New Mexico and 
 Arizona. One man in the Estancia Valley in New Mexico lost 50 
 per cent of his horses. A conservative stockman near Santa Rosa, 
 N. Mex., estimated that during one winter 50 per cent of the horses 
 and 10 per cent of the cattle perished. Around Jerome Junction, 
 Ariz., the estimated loss in the winter of 1906 was from 30 to 60 
 per cent, and correspondingly large losses were said to have taken 
 place about Flagstaff, Ariz. Blankinship says that in some parts 
 of Montana the loss of lambs reaches as high as 50 per cent. It 
 has been estimated that the annual money loss in Colorado is between 
 $1,000,000 and $2,000,000.
 
 DESTRUCTION OF LOCO WEEDS. 105 
 
 The death loss, however, may not be the largest factor in the 
 account. The loss from deterioration of stock and from premature 
 sales is very heavy. Many stockmen, when their herds commence 
 to eat loco, sell out rather than run the risk of having a lot of locoed 
 animals on their hands, and this loss means a very large reduction 
 in their profits. This, of course, is a loss that it is impossible to make 
 any estimate of. In many cases stockmen have been driven out of 
 the business by the weed, and have even gone into bankruptcy. In 
 some sections of Colorado, I am told, there are not more than one- 
 fifth of the animals on the range that were found a few years ago, 
 and this reduction of numbers is entirely on account of the loco. 
 When it is remembered that these losses occur more or less widely 
 through the semiarid region from the Canadian Provinces to Mexico, 
 it will be seen that the total loss from these plants is extremely large. 
 
 DESTRUCTION OF LOCO WEEDS. 
 
 The question is naturally raised as to whether some means can 
 not be devised of exterminating loco weeds from the range. The 
 most obvious w r ay of doing this is by cutting them out. This is 
 entirely feasible if the land is worth the price of the work. There 
 is an erroneous idea among many of the stockmen that plants will 
 grow from any part of the root, and that cutting the plants is useless 
 unless the whole root is dug up. While the plant is a perennial, the 
 buds are all at the crown, and if tlu's is cut off the plant is destroyed. 
 This is brought out by Professor Blankinship very clearly in liis 
 paper of 1906. Actual experiments in Hugo in connection with our 
 loco work there have proved the correctness of this view. Inas- 
 much as all the seeds do not germinate the first year, of course it is 
 necessary to repeat the cutting in successive years, but that it is 
 entirely possible to clear pastures of the loco there is no doubt. 
 
 Doubtless much can be accomplished by the use of a mowing 
 machine at the time of flowering. The flower scapes of AragaUus 
 lamberti are erect and a machine would cut out most of them and 
 thus spoil the seed crop. The work of cutting out, however, is not 
 as laborious as one might think, and it is very effective. 
 
 At the present time the most efficient way of combating the loco 
 seems to be to cut it out. Where pastures are fenced in this can be 
 done very easily. Astragalus mottissimus is much more easily cut 
 out than AragaUus lamberti, as it grows in patches and rarely in any 
 very large amount. On the open range, of course, this method of 
 exterminating the loco is impracticable. 
 
 In many cases much can l>e accomplished by keeping animals 
 away from ranges covered with loco during the time when feed is
 
 106 THE LOCO-WEED DISEASE OP THE PLAINS. 
 
 short, inasmuch as they are much more likely to contract the habit 
 when other food is lacking. Sometimes it may be profitable to 
 feed for a short time, in order that the habit may not be formed. 
 
 The question was raised whether it might not be possible to kill 
 out the loco plants by chemical means, that is, to use some sub- 
 stance that would kill the loco without injuring the grass. Although 
 the prospect was not very hopeful, it seemed worth while to try 
 the experiment. Plots of land were laid out with suitable control 
 plots, and experiments were made by sprinkling with varying 
 strengths of ammonium sulphate, copper sulphate, and iron sulphate. 
 From the use of ammonium sulphate and copper sulphate there 
 were no good results; if anything the loco seemed to grow more 
 luxuriantly. It at first appeared that certain strengths of copperas 
 were giving the desired results; the leaves of the loco were killed 
 while the grasses were uninjured. The thing appeared so hopeful 
 that an experiment on a larger scale was attempted, and a consid- 
 erable patch of ground on the ranch of Mr. Mclntyre, near Hugo, 
 was treated in the fall and left over winter, and then treated again 
 in the spring. It was thought that by this extended treatment it 
 would be possible to determine whether the poisoning was effective 
 or not. The result was, however, disappointing, and it was evident 
 that these substances could not be relied upon as exterminators of 
 the plant. 
 
 INSECTS DESTROYING LOCO PLANTS. 
 
 A large number of more or less destructive insects are found in 
 the loco plants. Of this number the larvae of Walshia amorphella, 
 a small moth, and those of Euxesta notata, a minute fly, are especially 
 active. They not only bore in the roots, but ascend into the leaf 
 stems and flower scapes, and when very abundant kill large numbers 
 of the plants. In 1905 it was noticed than an especially luxuriant 
 loco pasture, where the Astragalus mollissimus grew in large bunches 
 over a considerable area, was practically cleared of the plants in 
 less than a month's time, and during the remainder of the season 
 and through the summers of 1906 and 1907 very few plants were 
 found there. All along the line of the southern branch of the Union 
 Pacific Railroad in 1906 and 1907 there was a general destruction of 
 Astragalus mollissimus. There were few large plants, most of those 
 found being small, and in many cases they died early in the season. 
 It is noticed, too, that these larvae work so early in the season as very 
 largely to kill the plants before the seeds are matured. 
 
 a The insects mentioned under this heading have been identified by Dr. F. H. 
 Chittenden, of the Bureau of Entomology of the United States Department of Agri- 
 culture, and a paper on the insects known to infest the loco weeds has been published 
 as Bulletin 64, Part V, new series, of that Bureau (pages 33^12).
 
 INSECTS DESTROYING LOCO PLANTS. 107 
 
 From conversations with observant stockmen it appears that 
 Astragalus moUissimus comes and goes in cycles. Probably the insects 
 increase to such an extent as to destroy the loco; then, because food 
 is lacking, the insects largely die out, only to reappear again when the 
 loco gets another good start. 
 
 The same larvae live in AragaUus lamberti, but never seem to do so 
 destructive work in this plant. 
 
 The question naturally arises whether these insects can not be 
 encouraged and carried from place to place in order to exterminate 
 the loco plants in other areas. In the summer of 1906 the question 
 of colonizing the insects was raised in connection with our experi- 
 mental work, but it was hardly deemed practicable. An examination 
 of the more luxuriant loco pastures of western Nebraska showed 
 that the insects were already there, and were likely to increase as 
 rapidly as they would if we lent any additional aid. It appears 
 probable from our observations in Colorado that the insects, at the 
 present time, have put in their work so effectively that Astragalus 
 moUissimus is likely to be not, perhaps, a rare plant, but very much 
 reduced in numbers for possibly from two to five years. 
 
 The grub of Cleonus quadrilineata is especially destructive to 
 AragaUus lamberti. A. B. Clawson, field assistant in 1907, spent 
 considerable time in studying the w r ork of this insect, and while 
 his work is necessarily incomplete it is sufficient to indicate that 
 this is one of the most important factors in keeping down the num- 
 bers of the AragaUus lamberti plants. The larva of this beetle when 
 mature is very noticeable when one digs up the plants of AragaUus 
 lamberti by the roots. It is a large white grub, and either lives in 
 the roots or, in many cases, burrows in the outside of the root of the 
 plants. It was found in abundance as early as the latter part of 
 June. Perhaps more were found working upon the surface of the 
 root, but in many cases they worked inside and destroyed a large 
 part of the root of the older plants. It was noticed about the end of 
 the first week in July that the pupae were being found in the cases. 
 These cases were apparently made largely of dirt and are commonly 
 found on the side of the root, partly occupying spaces which had 
 been eaten out by the grub. The cases are about 20 to 25 mm. 
 long by perhaps half that in width, being irregularly oval in shape. 
 
 The first adult beetles were noticed coming from the pupal cases 
 toward the end of July. At this time and during the first part of 
 August the adults were quite fairly abundant. Just how much dam- 
 age these grubs do to AragaUus lamberti it is difficult to say. Certainly 
 they do not kill out the plants so thoroughly as those insects which 
 infest Astragalus moUissimus. Their main work seems to be confined 
 to the older plants, and, without any question, they hasten the death 
 of these plants. In some pastures where the AragaUus lamberti had
 
 108 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 grown into unusually large plants, it was noticed that they were all 
 being destroyed. The chief work of the larva seems to be in limiting 
 the number of years during which the plants may live. 
 
 It should be noted in this connection that the most destructive 
 work of this insect comes after the period of flowering and seed 
 formation, so that even when plants are killed they have already 
 produced the annual crop of seed. 
 
 EFFECT OF DRY SEASONS. 
 
 It is a matter of common remark among stockmen that the loco 
 weeds are most abundant in wet seasons. This is, doubtless, because 
 the seeds have a water-resisting coat and do not germinate except 
 under favorable conditions. Experimental attempts to raise loco 
 weeds have shown this to be the case. Mr. V. K. Chesnut tells me 
 that in Montana it was three years before they had a crop from sow- 
 ing the seeds. Our own experiments gave similar results. It is 
 not known how long the seeds will remain viable, but it is certainly 
 several years. 
 
 During the past dry seasons in Colorado the loco plants have 
 almost disappeared in some sections, this being probably due to 
 the combined influence of insects and meteorological conditions. 
 The insects have destroyed the old plants, and because of lack of 
 favorable conditions for germination, new ones have not come in to 
 take their place. 
 
 REMEDIES. 
 
 From the characteristics of the loco disease and its diagnosis, it is 
 seen that it is the result of long-continued feeding. In most cases 
 the amount of the plant eaten at any one time is small, much more 
 being eaten of the grasses than of the loco. The effects of the 
 poison in the more acute cases do not appear under about two weeks, 
 and in most of the adults only after weeks and even months of feed- 
 ing. Only very small doses of the poison are taken at any one time. 
 When an animal is finally locoed it may be assumed that there is 
 very little of the poison in its system in a form to be reached by an 
 antidote. While doubtless an antidote for the poison may be found, 
 it is not practicable to use the antidote as a remedy for chronic cases. 
 In cases of acute poisoning an antidote can be used, but in the slow 
 chronic cases it would be useless to attempt any such thing. It 
 would seem possible, however, by the use of an antidote to prevent 
 the original effects of the poison. Naturally the question arises as 
 to whether it may not be possible to immunize the animals by small 
 doses. From what has just been said it is evident that this is impos- 
 sible in a poison of this character. 
 
 In the way of remedies, from a medical standpoint, there would 
 seem to be three things to be attempted: First, to give something
 
 SUMMARY OF REMEDIES USED. 109 
 
 that would destroy the appetite for loco; second, to give an antidote 
 to counteract the effects of the poison; and, third, to give such rem- 
 edies as would counteract the general effect of the poison and aid the 
 animal in recovery. The chances of finding a substance that in one 
 or a few doses would destroy the appetite for loco are not very great. 
 Some attempts were made in this line, but, as perhaps might have 
 been expected, were unsuccessful. Doctor Crawford's report on the 
 finding of barium in the plants was made so late that no experimen- 
 tation in regard to an antidote for this substance was possible, and 
 this part of the work will have to be taken up later. 
 
 It seemed more hopeful to make the attempt to give remedies for 
 the general condition of the animals with the hope of aiding them in 
 building up against the effects of the poison. As has been indicated 
 in the diagnosis, the chief effect of the poison is on the central nerv- 
 ous system, and this results not only in the marked nervous phe- 
 nomena, but in anemia and general debility. In seeking a remedy, 
 then, it seemed desirable not to attempt to use an antidote for the 
 poison, but to use such remedies as would affect the nervous system 
 and aid the animal in getting out of the anemic condition which is 
 so pronounced. All the remedies tried had this end in view to build 
 up the patient with especial reference to the nervous system. 
 
 Some attempts at remedial measures were made in 1906. In the 
 summer of 1907 this work was prosecuted more vigorously on the 
 lines which were indicated by the results of the previous summer. 
 Inasmuch as most chronic cases of loco are constipated, in all of the 
 treatment we made sure that there was free action of the bowels. 
 This was secured by occasional doses of Epsom salts, the condition of 
 the animals being watched from day to day. During the summer of 
 1907 especial attention, too, was paid to the diet. All animals under 
 treatment were fed a little grain daily. With this was mixed a little 
 oil meal because of its laxative properties. When it was necessary 
 to feed hay, alfalfa was used, largely because it also is laxative. 
 
 The remedies experimented with in 1906 were strychnin, potas- 
 sium iodid, asafetida, caffein, arsenious acid, Fowler's solution, and 
 valerian. As the result of this work wo felt convinced that asafetida, 
 valerian, caffein, and potassium iodid gave no good effects. In tho 
 use of strychnin the results were a little doubtful. Two of tho cattle 
 were cured during the strychnin treatment and there seemed no good 
 reason why this drug should not have the credit of tho euro, but it 
 was true that other animals treated with strychnin died, in somo 
 cases partly at least as the* result of tho poison. Xono of tho horses 
 showed improvement from tho use of strychnin. Tho fact that sev- 
 eral of tho animals showed indications of poisoning mado it prolmhlo 
 that strychnin was administered in too largo doses, although only 
 tho minimum doses of tho ordinary veterinary matoria modica woro 
 used. It seemed probable that locoed animals woro, perhaps, more
 
 110 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 sensitive to the effects of strychnin and should be treated in espe- 
 cially small doses. 
 
 Arsenious acid effected a cure in one of the horses. This animal 
 was treated at the Colorado Agricultural Experiment Station during 
 the winter of 1906-7 under the general direction of Doctor Glover, 
 and, while it was a clear-cut case of loco disease in the fall of 1906, 
 with all the typical symptoms, it came out in the spring definitely 
 and apparently permanently cured. This animal was used as a sad- 
 dle horse during the summer of 1907 and at no time showed any of 
 the signs of loco poison, if we except a slight loss of spirits. 
 
 One of the cattle, too, after it was treated with Fowler's solution 
 was completely cured. 
 
 TREATMENT OF CATTLE IN 1907. 
 
 Fowler's solution. Only one animal was treated with Fowler's solu- 
 tion in 1907. This steer was cured, but the cure was much slower 
 than in some of the other remedies, although the subject was a fav- 
 orable one. 
 
 Atoxyl. One steer was treated with atoxyl and recovered. Two 
 others did not do well and were afterwards put on strychnin and 
 improved. The results from the use of atoxyl were not considered 
 favorable. 
 
 Sodium cacodylate. Five cattle were treated with sodium cacody- 
 late. Of these 1 died, 1 improved, and 3 were cured. The one that 
 died was an especially bad case and nearly hopeless from the start. 
 The net result from the use of sodium cacodylate was very favorable. 
 
 Strychnin. Fourteen head of locoed cattle were treated with 
 strychnin. Two of these were of the experiment stock, while the 
 others were brought in from ranches in the neighborhood for treat- 
 ment. Of these 14, 2 showed improvement, 3 died, and 9 were cured. 
 Of those that died one was very much improved so far as the loco 
 poison was concerned, but died of pericarditis. The other two were 
 very bad cases and one of them died by drowning, being too weak to 
 get up after falling with its nose under water. One was treated with 
 strychnin followed by sodium cacodylate, followed by another course 
 of strychnin, being treated in all fifty-one days, and was discharged 
 cured. 
 
 Strychnin and sodium cacodylate. Two were treated with strychnin 
 and sodium cacodylate at the same time and were cured. 
 
 TREATMENT OF HORSES *IN 1907. 
 
 . Seven horses and 1 mule were under treatment in 1907. In all 
 these cases Fowler's solution was used, but one was also treated with 
 strychnin and sodium cacodylate. No good results appeared from 
 the use of the strychnin and sodium cacodylate. The mule died. It
 
 GENERAL RESULTS OF TREATMENT. Ill 
 
 was an old animal and a chronic loco, and the combination of troubles 
 carried it off in spite of treatment. Old age without any doubt was 
 an important factor hi causing its death. Two of the others were not 
 treated long enough for final results, but gave promise of recovery. 
 Two showed distinct gain, but were not considered as positively cured. 
 Two were distinctly cured. 
 
 GENERAL RESULTS OF TREATMENT. 
 RESULTS WITH CATTLE. 
 
 A careful study of the cases of cattle which were treated in the two 
 summers leads to these conclusions: 
 
 1. Very advanced cases are generally hopeless; occasionally they 
 may be cured, but ordinarily they will die. 
 
 2. Cattle may recover without any treatment if they are taken from 
 loco and put upon good feed. There was one marked case of this kind 
 in our herd hi the summer of 1907. 
 
 3. Atoxyl is not effective as a remedy. 
 
 4. Fowler's solution is of doubtful efficacy. 
 
 5. Good results almost invariably follow the use of sodium cacody- 
 late or strychnin, or the two used together. We felt the most certain 
 of good results under the strychnin treatment. This opinion was 
 reached partly as the result of a statistical study of the cases and 
 partly as the result of the general impression made upon us in the 
 course of treatment. Whenever, during the summer, we were par- 
 ticularly anxious that a given animal should recover, our tendency 
 was always to put it upon the strychnin treatment. 
 
 RESULTS WITH HORSES. 
 
 The net result of the work of the two summers on horses shows: 
 
 1. As in cattle, advanced cases are hopeless. 
 
 2. As hi cattle, recovery is possible in mild cases without treatment. 
 
 3. Strychnin does not give good results. 
 
 4. Fowler's solution can be used with the expectation of beneficial 
 results. 
 
 PERMANENCY OF LOCO CURES. 
 
 It must not be supposed that an animal cured of loco will never eat 
 the weed again. Probably in most cases if they have an opportunity 
 they will go back to their old habits. When a horse has been cured it 
 should be kept in a pasture free from loco. When a steer has been 
 cured, it is probably best to put him upon the market as soon as he 
 is in sufficiently good flesh rather than to run any rusk of a second 
 I>eriod of loco poisoning. It is rather interesting in this connection, 
 however, that the two head of cattle which were cured in 1006 and 
 were pastured on loco in 1907 continued in the loco pasture the whole
 
 112 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 season, eating more or less of the weed, probably rather less, and 
 showed little effect. It seems rather probable than in many of the 
 cured cases they are not as likely to go back to eating loco as are 
 animals that have never been subjected to its temptations before. 
 
 PREVENTION OF LOCO POISONING. 
 
 Not all animals will contract the loco habit, and those that do so 
 will ordinarily commence the eating at a time when feed is short. It 
 is a matter of common knowledge among stockmen that it is during 
 the winter and spring seasons that animals are most likely to com- 
 mence eating the loco weeds. This is especially noticeable in the 
 spring, when the grass of the preceding season has been largely grazed 
 off and the new grass has not started. At this time the loco weeds 
 are, in ordinary seasons, green and attractive, and are frequently 
 the most prominent plants in the plains vegetation. Thus many ani- 
 mals, forced by hunger, commence to eat the weeds, and while some 
 of them abandon the loco after the grass starts, others contract the 
 habit, which continues even after there is an abundance of good feed, 
 and leads eventually to their death. 
 
 Much can be accomplished by the stockmen at this season in the 
 way of prevention. In localities where the loco is largely confined 
 to definite areas of the range it is possible to keep the animals away 
 from the loco until after the grass has started, when there is likely to 
 be very little trouble. In some cases feeding for a short period will 
 bridge over the dangerous time, and while it may seem somewhat 
 expensive to feed, it is evidently better than to have the stock die. 
 
 SUMMARY OF WORK ON REMEDIES." 
 
 1. Some locoed animals will recover if taken from the weed and 
 fed well, without any treatment. 
 
 2. Most locoed animals will recover if they are taken from loco, 
 fed carefully, and treated on the lines indicated by our experiments. 
 
 3. In all cases care should be taken to relieve constipation, either 
 through the character of the food or by the use of magnesium 
 sulphate. 
 
 4. Horses are best treated with Fowler's solution in daily doses of 
 15 c. c., continued for at least one month. 
 
 5. Cattle are best treated with daily doses of strychnin, the doses 
 not exceeding three-twentieths of a grain, given hypodermic ally, and 
 continued for one or two months. It is especially important that 
 the dose should be small, as locoes are very susceptible to the bad 
 effects from overdosing. 
 
 a Further work on remedies during the summer season of 1908 confirmed the con-< 
 elusions of the preceding years.
 
 GENERAL SUMMARY. 
 
 For many years complaints have been made of the losses of cattle, 
 horses, and stock in the semiarid region of the West from a disease 
 which is popularly known as "loco," this name being given because 
 of the crazy symptoms of the affected animals. The disease is preva- 
 lent from the Canadian provinces on the north to Mexico on the 
 south, and the losses have been very great; so great, in fact, that in 
 some sections stockmen have been thrown into bankruptcy, and 
 sometimes most of the animals have been taken off the range. Some 
 years ago the State of Colorado created a bounty for cut and dried 
 loco, but such a large amount of it was collected and the bounty pay- 
 ments amounted to such large sums that the law was repealed for 
 fear that the whole State would be thrown into bankruptcy. 
 
 Generally speaking, among the stockmen of this region the cause 
 of the loco disease has been ascribed to certain leguminous plants 
 known as the loco weeds, the chit f of these being Astragalus moUissi- 
 mus and Aragattus lamberti. During the last quarter of the nine- 
 teenth century this subject was investigated by a large number of 
 people, but with very contradictory results. Attempts were made 
 to isolate a poison from the loco plants, which succeeded apparently 
 in the hands of certain authors, but the results of their work were 
 not corroborated by others. Scientific men traveled largely through 
 the loco region to observe conditions, and autopsies were made on a 
 considerable number of animals. While it was evident that a dis- 
 ease of some kind was causing enormous losses through this semiarid 
 country, the general result of the investigations of scientific men was 
 to lead them to be veiy skeptical in regard to the supposed poison- 
 ous properties of the loco plants. It was noticed that most of the 
 so-called locoed animals had been Subjected to an unfavorable envi- 
 ronment, especially in the way of feed, and the consensus of opinion 
 among investigators seemed to be that some cause for the disease 
 must be sought other than the loco plants. Some of the stockmen 
 themselves were very skeptical in regard to the poisonous properties 
 of the plants, and contended that with proper feed there would be no 
 such thing as locoed animals. 
 
 Inasmuch as the losses were so heavy and the stockmen were 
 
 anxious to have the subject investigated moro thoroughly, the United 
 
 States Department of Agriculture instituted nn experiment in the 
 
 summer of 1905 upon a larger and more thorough scale than had been 
 
 79154 Bull. 11209 8 U3
 
 114 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 attempted before, hoping to prove or disprove the poisonous proper- 
 ties of the loco weeds. This experiment consisted in feeding cattle 
 and horses upon pastures containing loco weed in comparison with 
 others fed on pastures that were free from the loco weed, as well as 
 feeding the loco plants in the corrals, and of making as extensive 
 autopsies upon locoed animals as possible. 
 
 The experiments were intended (1) to prove whether the loco weeds 
 would poison or not, (2) to demonstrate the symptoms of loco 
 poisoning and the pathological lesions accompanying it, and (3) to 
 determine whether or not remedial measures could be instituted for 
 the relief of the loco-infested area. 
 
 The conclusions reached as the result of the work of three seasons 
 are as follows: 
 
 1. There is no longer any question in regard to the poisonous prop- 
 erties of the loco plants. It was clearly demonstrated that animals 
 eating these plants would succumb sooner or later to their poisonous 
 action. This work, too, was abundantly corroborated by the phar- 
 macological work of Doctor Crawford in the laboratory at Washing- 
 ton, by whom a poison was separated which was fatal to rabbits. 
 
 2. It was found that the symptoms of the loco disease were essen- 
 tially like those which had been mentioned by the majority of stock- 
 men. It was found that some of the symptoms were exaggerated, 
 but, on the whole, the statements of the stockmen were amply 
 corroborated. The more prominent symptoms are a staggering and 
 uncertain gait, caused by a general disturbance of the nervous 
 system, which leads in some cases to an apparent partial paralysis 
 of the limbs and to a very distinct lack of muscular coordination. 
 The animals eating loco eat more and more of it, although they do 
 not in all cases acquire a passionate love for the weed, and sooner 
 or later lose flesh and die of starvation. 
 
 3. In the post-mortem examinations it was found that there were 
 certain quite definite lesions. The animals were strongly anemic. 
 This anemia was indicated not only by paleness of flesh and actual 
 loss of blood, but by serous deposits in various parts of the body. 
 The blood was found to be poor in hemoglobin and commonly rather 
 rich in leucocytes. A diseased condition of the stomach was a com- 
 mon accompaniment of the locoed condition, this being marked in 
 cattle by ulcers in the fourth stomach. All the body fluids are 
 rather unusually abundant, and this is particularly true of the fluid 
 of the epidural space of the spinal canal, which is commonly more or 
 less organized, so that the spinal canal frequently seems to be filled 
 with a jelly-like substance. There is a hyperemic condition of the 
 central nervous system, which in acute cases is accompanied by 
 clots in the lateral ventricles. In females diseased ovaries are 
 common.
 
 GENERAL SUMMARY. 115 
 
 4. The common loco plants in Colorado and adjacent territory are 
 AragaUus lamberti and Astragalus moUissimus. Of these the more 
 widely distributed is AragaUus lamberti, commonly known as the 
 "rattleweed" or "white loco." The results of the experiment 
 showed very clearly that Astragalus moUissimus was much the more- 
 virulent of the two species under consideration. This plant is more 
 abundant in the southern part of the semiarid region, although not 
 confined to that. In Colorado it is commonly found in the depres- 
 sions and on adobe soil, while AragaUus lamberti is found upon the 
 hillsides and upon sandy soil. AragaUus lamberti is not only com- 
 mon on the plains, but also extends in the mountains to an altitude 
 of perhaps 8,000 feet. 
 
 5. Horses, cattle, and sheep are somewhat differently affected by 
 these plants. In regions covered with Astragalus moUissimus the 
 only common locoed animals are horses. Horses which eat this 
 plant become poisoned ordinarily rather quickly and may die in a 
 comparatively short time. Both cattle and horses eat AragaUus 
 lamberti, but cattle, perhaps, rather more freely than horses, so that 
 in regions where AragaUus lamberti is the more common loco plant 
 the cattle are much more commonly affected than horses. In locali- 
 ties where Astragalus moUissimus is the only loco plant locoed cattle 
 are very rare, indeed. Sheep eat both species, but for them also 
 AragaUus lamberti is the more dangerous, inasmuch as they are more 
 apt to eat this plant than Astragalus moUissimus. 
 
 6. It was found that there is a great difference in the individual 
 susceptibility of animals to the loco poison, although most of them will 
 succumb to the temptation and perish from its effects sooner or later. 
 In regard to different breeds of animals there is a distinct differ- 
 ence, although the observations were not extensive enough for any 
 broad generalizations. Generally speaking, the better-bred animals 
 are more likely to be poisoned than those that have become accus- 
 tomed to the country. Among sheep, black-faces yield much more 
 quickly than Merinos. Among cattle, Durhams and Aberdeen- Angus 
 were found to yield more quickly than Herefords. 
 
 7. In regard to remedial measures, the work of the experiment gives 
 quite definite suggestions. It is clear that where land is sufficiently 
 valuable to make it profitable to pay for that amount of labor, it is 
 entirely feasible to cut out all of the loco weeds. This is particularly 
 easy in regard to Astragalus inoU'mmntmt, because it grows in compara- 
 tively small patches. Where AragaUus lamberti is abundant the work 
 would be more difficult , and in some cases the land is hardly worth the 
 expense of the labor. It is evident that in the case of fenced pastures 
 it frequently will be profitable to destroy the loco weeds in this way.
 
 116 THE LOCO- WEED DISEASE OF THE PLAINS. 
 
 In the case of open range it is probably impracticable to arrange any 
 means of doing this. 
 
 In many cases much can be accomplished by keeping animals away 
 from ranges covered with loco during the time when feed is short, 
 inasmuch as they are much more likely to contract the habit when 
 other feed is lacking. Sometimes it may be profitable to feed for a 
 short time, in order that the habit may not be formed. 
 
 It is absolutely necessary that animals which have acquired a taste 
 for loco should be removed from temptation. 
 
 Except in very advanced cases, the treatment of locoed animals can 
 be undertaken with every reason to expect good results. The first 
 essential, of course, is to remove to a pasture which is free from loco. 
 Their feed should be so regulated as to produce looseness of the bow- 
 els, or if this can not be done they can be dosed with some laxative, 
 such as magnesium sulphate. Green alfalfa is one of the best feeds. 
 If the animals are being fed on grain, it is well to mix oil meal with the 
 grain. The necessity of producing a loose condition of the bowels can 
 not be too strongly emphasized. 
 
 Some animals will recover under this treatment without recourse 
 to medicine. With most animals, however, recovery is hastened by 
 the administration of strychnin or sodium cacodylate, or both, in 
 the case of cattle, and of Fowler's solution in the case of horses. All 
 these medicines should be given in small doses and continued for a 
 considerable period of time, seldom less than thirty days. The daily 
 doses of strychnin should not exceed three-twentieths or four- 
 twentieths of a grain (or 0.009 to 0.012 gram). Sodium cacodylate 
 should be given in daily doses of 6.2 grains (or 0.4 gram). The 
 strychnin and sodium cacodylate are best given by hypodermic injec- 
 tion. Fowler's solution should be given in doses of 15 to 20 c. c. in 
 the grain or in the drinking water. 
 
 Recovery will in most cases be slow, as should be expected from 
 the slow incipience of the disease ; but care will bring the animal to a 
 practical cure in the majority of cases. Cured animals do not seem 
 as likely to eat the loco again, but it is best not to subject them to 
 temptation.
 
 BIBLIOGRAPHY. 
 
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 AMERICAN VETERINARY REVIEW. 
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 BREWER, W., and WATSON, S. 
 
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 BULLETIN OK PHARMACY. 
 
 1801. Further investigation of loco weed. Vol. 5, No. I, p. 8. 
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 117
 
 118 BIBLIOGRAPHY. 
 
 CHESNUT, V. K. 
 
 1898. Preliminary catalogue of plants poisonous to stock. U. S. Department 
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 CHESNUT, V. K., and WILCOX, E. V. 
 
 1901. The stock poisoning plants of Montana: A preliminary report. U. S. De- 
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 CHRISTY, R. M. 
 
 1887. Notes on the botany of Manitoba. Journal of Botany, vol. 25, pp. 271-276, 
 
 290-301. 
 COLLIER, P. D. 
 
 1879. "Loco," or poison weed. U. S. Commissioner of Agriculture, Annual 
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 CORNHILL MAGAZINE. 
 
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 BIBLIOGRAPHY. 119 
 
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 124 BIBLIOGRAPHY. 
 
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 BIBLIOGRAPHY. 125 
 
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 INDEX. 
 
 Page. 
 
 Abortion produced by loco 21,25,61,94 
 
 Age susceptibility 102 
 
 Antelopes poisoned by loco 24, 104 
 
 Aragallus albiflorus, synonym of Aragallus lamberti 38 
 
 Aragallus lamberti 
 
 Description, distribution 37 
 
 Experimental feeding 47-68 
 
 Less poisonous than Astragalus mollissimus 101 
 
 Aragallus sericeus, synonym of Aragallus lamberti 38 
 
 Aragallus spicatus 30, 38 
 
 Aragallus splendens 30 
 
 Arizona, loco poisoning in 40 
 
 Arsenic, treatment with, in 1906 78 
 
 Astragalus arrectus 32 
 
 Astragalus bisulcatus 25 
 
 Astragalus caryocarpus 17 
 
 Astragalus crotalariac 17, 18 
 
 Astragalus dorycnioides 28 
 
 Astragalus haydeniensis 25 
 
 Astragalus hornii 16, 1 7 
 
 Astragalus lagopus 28 
 
 Astragalus lentiginosus 16. 18 
 
 Astragalus lentiginosus var. fremonti 17 
 
 Astragalus loliflorus 25 
 
 Astragalus menzifsii 16 
 
 Astragalus mollissimus 
 
 Description 38 
 
 Distribution 39 
 
 Experimental feeding 45, 47, 48, 50, 51, (52 
 
 More poisonous than Aragallus lamberti 101 
 
 Astragalus mortoni 17 
 
 Astragalus oocarpa 17 
 
 Astragalus palousensis 28 
 
 Astragalus purshii 32 
 
 Astragalus reventus 32 
 
 Astragalus sftaldingii . 2S. 32 
 
 Astragalus spicatus * 28, 29 
 
 Astragalus splendni* 2X, 29 
 
 Atoxyl, experiment** with S3 
 
 Bibliography 117 
 
 Bifon, distribution of lorn WM-dn by 40 
 
 Black-face sheep more easily affected than merinoe 102 
 
 127
 
 128 INDEX. 
 
 Page. 
 
 Blood, examination of, in locoed animals 95 
 
 Breeds of animals, different, effect of loco on 102 
 
 Cattle- 
 Experimental feeding of 47, 56, 71 
 
 Experiments with remedies in 1907 83 
 
 Summary of treatment of, in 1907 110 
 
 Cause of loco disease 91 
 
 Cleonus quadrilineata 107 
 
 Conclusions derived from literature 34 
 
 Cycles, loco growth in 107 
 
 Cysticercus tenuicollis 31 
 
 Darling pea, poisonous to stock 41 
 
 Distribution of Aragallus lamberti and Astragalus mollissimus 37 
 
 Dry seasons, effect of, on loco 108 
 
 Durham cattle more easily affected than Herefords 102 
 
 Emmenagogue, loco as an 21 
 
 Euxesta notata 106 
 
 Experimental work, scope and details 42 
 
 Experiments at Woodland Park, Colo 71 
 
 Experiments with cattle 
 
 First season 47 
 
 Second and third seasons 56 
 
 At Woodland Park, Colo 71 
 
 Experiments with horses 
 
 First season 49 
 
 Second and third seasons 62 
 
 At Woodland Park, Colo 71 
 
 Experiments with sheep 66 
 
 Extermination of loco weeds 30, 105 
 
 Fertile soil, relation to loco plants 40 
 
 Fowler's solution, experiments with 83 
 
 Goat, locoed 53 
 
 Gompholobium, loco weed in Australia 24 
 
 Hasmonchus metastrongylus 31 
 
 Hemolymph glands in locoed animals 97 
 
 Hereford cattle less affected than other breeds 102 
 
 Historical summary of loco disease 15 
 
 Horses 
 
 Experimental feeding of 49, 62, 71 
 
 Experiments with remedies in 1907 88 
 
 Summary of treatment of, in 1907 J10 
 
 Imperial, Nebr., experiment at 73 
 
 Indigo 
 
 Disease 28 
 
 Plant 41 
 
 Insects destroying loco plants 106 
 
 Lambs peculiarly susceptible to loco poisoning 95 
 
 Lesions, pathological, of loco victims 95 
 
 Leucocrinum montanum 22 
 
 Literature of loco disease 
 
 Conclusions from 34 
 
 Summary and review . 15 
 
 Loco cures, permanency of ...,.., , , . r . . Ill
 
 INDEX. 129 
 
 Page. 
 
 Loco, origin of name 15 
 
 Loco plants, list of 36 
 
 Loco poison 
 
 Amount necessary to poison 100 
 
 Effect on man 104 
 
 Prevention of 112 
 
 Susceptibility of different breeds of animals 1C2 
 
 Time before symptoms appear 1,8 
 
 Virulence 98 
 
 Loco weeds, destruction of 105 
 
 Lasses from loco poisoning 104 
 
 Malvastrum coccintum 24 
 
 Man 
 
 Alleged poisoning by loco 25 
 
 Susceptibility to loco poisoning 104 
 
 Merino sheep less affected than black faces 102 
 
 Mule, experimental feeding of 64 
 
 Mules, susceptibility to loco poisoning 103 
 
 " Nenta disease " of South Africa 29, 41 
 
 Nervous system in locoed animals 97 
 
 New Mexico, loco poisoning in 40 
 
 Northwest Territories, loco in 28, 29, 31 
 
 (Estrus ovis in sheep, symptoms like loco 66, 68, 69, 70 
 
 Ovaries, diseased, in locoed animals 98 
 
 Oxytropix lamberti 16, 1 7, 18, 19, 21, 22, 23, 24, 25. 28. 29 
 
 Pastures used in experimental work, description of 44 
 
 Pathological lesions of locoed animals 95 
 
 Pea-eating disease 29 
 
 Permanency of loco cures Ill 
 
 I'hysostigma renenosum 'J4 
 
 Plants known as loco plants 36 
 
 Prevention of loco poisoning , . . . . 112 
 
 Problem of loco poisoning, statement of 42 
 
 Rattlesnake weed 28 
 
 Remedies 
 
 Discussion 73, 108 
 
 Experiments with catt le in 1907 S3 
 
 General summary 112 
 
 Proposed in literature 32 
 
 Results in 190(5 SI 
 
 Result* and conclusions from experiments. . 91 
 
 Review of literature 15 
 
 Sagebrush, poisoning by 11 
 
 Sarrr>rystix tetirlla : i 1 
 
 Sheep 
 
 Experiment* and discussion (>>, !> 
 
 Experiment* with remedies in 1907 90 
 
 SfKliurn cacixlylate, ex{>eriment* with s;{ 
 
 Boil, relation of loco plants to to 
 
 Snphnra nrrirra Hi 
 
 Spinal column, wmu* exudutc 
 
 Stijm viriduln 
 
 79164- -Hull. 11209 9
 
 130 INDEX. 
 
 Page. 
 
 Stomach, diseased condition of, in locoed animals 23, 97 
 
 Strychnin-- 
 Experiments with cattle in 1907 86 
 
 Treatment with, in 1906 75 
 
 Summary 
 
 General 113 
 
 Of first season's work 54 
 
 Susceptibility of different breeds of animals to loco poison 102 
 
 Swainsona galegifolia 41 
 
 Symptoms 
 
 Of loco poisoning 92 
 
 Mentioned in literature 32 
 
 Temperature of locoed animals . 95 
 
 Time required to produce loco poisoning 98 
 
 Thysanosoma actinioides 31, 66 
 
 Treatment, general results 81, 111 
 
 Ulcers in stomach 23, 97 
 
 Virulence of loco poisoning 98 
 
 Walshia amorphella 106 
 
 Woodland Park, Colo., experiment at 71 
 
 Zygadenus elegans 22
 
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