' cL LIBRARY UNIVERSITY OF CALIFORNIA. Received.... JL/^&W /^? ^ B'OLOCY Shelf A \>. UB * A KY X fc -J ON THE RELATIONS OF MICRO-ORGANISMS TO DISEASE. THE CARTWRIGHT LECTURES, DELIVERED BEFORE THE ALUMNI ASSOCIATION OF THE COLLEGE OF PHYSICIANS AND SURGEONS, NEW YORK, FEBRUARY 19, 21, 24 and 27, 1883. BY WILLIAM T. BELFIELD, M.D., Lecturer on Pathology, and on Genito-Urinary Diseases (Post-Graduate Course), Rush Medical College, Chicago. Reprinted from THE MEDICAL RECORD, February and March, 1883. CHICAGO: W. T. KEENEK, 96 WASHINGTON STREET. 1883. LIBRARY G ON THE RELATIONS OF MICRO-ORGANISMS TO DISEASE. LECTURE I. Mr. President and Gentlemen : In accepting your flat- tering invitation to deliver the Cartwright lectures, I have, in compliance with your request, selected my present subject almost the only one indeed which I would venture to discuss in your presence not simply because of its intrinsic importance and interest, but also because there exists in the medical public of our land a diversity of opinion concerning it, which is not, in my estimation, warranted 'by the facts. For since trust- worthy original investigations in this direction, demand- ing continuous devotion of the observer to the subject and the renunciation of other pursuits ; demanding spe- cial training and experience ; requiring laboratory and other expensive facilities ; since such investigations, possible therefore in general only through State or cor- porate assistance, have been, and under existing cir- cumstances must be made almost exclusively in other lands than ours ; since, further, important results at- tained within recent years and published in foreign tongues have been as yet but partially incorporated in our standard literature ; since the tendency of the prac- tising physician to which category we all, with rare ex- ceptions, of necessity belong is ever toward the culti- vation of the art rather than the science of medicine ; since, finally, there is a prevalent disposition to ignore the entire subject as trivial or fanciful ; for these, and perhaps other reasons, there prevail, as it appears to me, some misconceptions as to the present state of knowl- edge on this subject. It shall be, accordingly, my effort to present in these lectures no original investigations, no theories nor views, but simply the facts already estab- lished, and the deductions incident thereto an effort which I am encouraged to undertake by some familiarity with pertinent literature, and by some little practical knowledge of the methods and manipulations involved. In order to discuss intelligibly the more recent and familiar subjects, such as the r61e of the bacillus tuber- culosis, we must bear in mind certain facts, less sensa- tional and perhaps less widely known, concerning the life-history of microscopic parasites. Although even the early microscopists. beginning with Leeuwenhoeck (1675), observed and studied bacteria; although these minute bodies were observed in animals dead of septic infection by Fuchs, in 1848, and in the blood of sheep dead of anthrax by Brauell and Davaine, in 1849 an d 1850, no effort appears to have been made to establish a genetic relation between the plants and the disease until the publication of Pasteur's work on fer- mentations, in 1 86 1. Then the bacteria which had been the unenvied monopoly of biologists suddenly acquired deep interest for pathologists. The experimental work on septic infection, by Mayerhofer, Coze and Feltz, Rind- fleisch, Waldeyer, and Recklinghausen, in 1865, 1866, and 1867, drew the attention df the medical public to the subject Meanwhile Lister, impressed with the results of Pasteur's work, and desperate (as I was informed by a Glasgow neighbor of his) at the death from pyaemia of several cases in rapid succession, anticipating the te- dious progress of experimental science, submitted the question to empiric arbitration on the operating table. His clinical results revolutionized surgical methods on the one hand and infused new vigor into experimental pathologists on the other ; the number of workers and of works so rapidly increased that to-day simple mention of the literature of this subject would be the work of hours, I deem it, therefore, inexpedient to attempt, in 5 the limited time at my disposal, a historical sketch of the development of the question, and shall endeavor to pre- sent merely the present knowledge of the subject, with a review of the evidence upon which it rests. Fungi plants which, because devoid of chlorophyll and therefore unable to fabricate the necessary hydro- carbons, are usually parasitic upon animal or vegetable tissues, living or dead may be divided into three general classes : i, the mould fungi (aspergillus varieties, for example) ; 2, the budding fungi (e.g. t the yeast plant) ; and, 3, bacteria, or dividing fungi. Bacteria were denned in 1875 by Cohn as "cells de- void of chlorophyll, of spherical, oblong, or cylindrical, sometimes twisted or sinuous form, which reproduce themselves exclusively by transverse division and live either isolated or in families." This definition requires to-day but one modification ; reproduction, namely, is known to occur in several species, at least by the forma- tion and liberation of spores as well as by fission. The bacteria consist of a nitrogenous, highly refractive, usually colorless substance, protoplasm or mycoprotein (Nencki), imbedded in which glistening, oily looking granules can sometimes be observed. The bacterium exhibits a power of resistance toward acids and alkalies which could not be possessed by a nitrogenous substance ; hence it was assumed by Cohn that the external layer is a sheath of cellulose or similar hydrocarbonaceous material, such as the mould-fungi are known to possess. Although there has been as yet no decisive ocular demonstration of the existence of this membrane, the reactions of certain spe- cies toward straining fluids corroborate the assumption. Many of the elongated bacteria have been demon- strated to possess also a thread like projection from the extremity, a flagellum or cilium ; these, as well as- some other varieties not yet proven to possess flagella, are capable of independent, often rapid locomotion in liquids; others are devoid of flagella, and incapable of motion ; hence it is highly probable that the power of locomotion is associated with the possession of cilia. Beyond this 6 bacteria seem to possess no differentiation of structure nor localization of function ; nutrition and assimilation are processes of osmosis. This simplicity of structure and function has given rise to discussion as to whether they should be regarded as animals or vegetables ; the question is, of course, merely a technical one of classification; since the features which distinguish the higher animals from the higher plants disappear as we descend the scale of organic life until few or none remain ; yet because almost all of the simplest organisms hitherto called ani- mals, the flagellata, possess a rudimentary mouth and are capable of absorbing solid food, while the simplest plants are not so characterized, the bacteria have been assigned to the vegetable kingdom. Whether they should be called algae or fungi is a question for botanists to decide ; the power of independent motion exhibited by some varieties suggests affinity with the algae ; but the absence of chlo- rophyll is generally considered to require their classifica- tion among the fungi. / The necessities of their existence are as simple as those ' of the mould fungi ; indeed, so nearly identical as to re- quire no discussion. As to the chemical reactions inci- dent to their vital activity, our present knowledge is very scanty ; one variety is known to induce the transformation of grape and milk sugar into lactic acid ; another the de- composition of glucose or lactic acid with formation of butyric acid ; another the change of urea into carbonate of ammonia ; some produce pigments, blue, red, yellow ; of many we know only that they transform a solid sub- stance gelatine, for example into a liquid ; but one of the most important facts in regard to them is the proof that putrefaction of albuminous substances is a phenom- enon incident to the vital activity of certain varieties the bacterium termo and probably others as must be admitted by every one familiar with the work of Pasteur, Tyndall, and their pupils. Until the chemistry of their vital processes is ascertained, it will be impossible to as- sert how they can be injurious to a living tissue, whether by simple mechanical irritation, by the appropriation of oxygen and other nutritious elements, by the excretion of substances injurious to animal cells, or in several of these ways combined. The formation of substances in- compatible with the life of the animal cells seems to play a prominent role in the production of injurious effects by at least some varieties. The simplicity of organization and vital requirements explains their extensive distribution in nature : every moist substance of organic origin and all water contain- ing even a trace of organic matter is favorable soil for one or more varieties ; the upper layers of the earth, containing these essential ingredients, and remaining comparatively warm, constitute a continual breeding- place for these organisms. The minuteness and light- ness of bacteria explain their presence in the atmos- phere ; they are swept by currents of air from dry or moist surfaces ; they float in clouds of dust ; they are carried by insects ; the persistence of their vitality, the rapidity of their propagation, result in practical ubiquity. Direct microscopic observation of atmospheric dust, and the experiments of Tyndall with the electric beam in a dark chamber, have shown that wherever we find dust, at moderate temperature and altitude, we may expect to find bacteria. Yet the atmospheric bacteria are probably not so numerous as has been pictured. The observations of Miquel and of Koch show that even in a laboratory many litres of air contain no organisms. Whether or not bacteria are swept from surfaces of liquids ; whether after once drying upon a given surface they can be removed by air-currents, are as yet undecided questions which may have practical bearings in the future. At present we know no laws of atmospheric distribution wherein bacteria ex- hibit other behavior than particles of dust in general. The champions of spontaneous generation, compelled to surrender their maggots in decaying meat to the sim- ple demonstration that covering the meat with fine gauze, which prevented the access of flies, prevented also the development of maggots; forced to abandon intestinal worms by the successive demonstrations of numerous observers that each worm proceeded, though often by devious ways, from a similar pre-existing organism ; found a tower of strength in the bacteria, a position fortified by a series of careful, conscientious, and delicate ex- periments by Bastian and Pouchet. The result of that contest is known to all. The errors in manipulation and interpretation upon which the proof of sponta- neous generation rested were detected, and a series of hitherto unassailable experiments by Pasteur, Tyndall, Traube, and Brefeld compelled the admission that bac- teria, like the intestinal worms and the maggots, and all other living things, illustrate the dogma, " oinne vi- vum ex ovo ! " Yet this phantasy of spontaneous gene- ration seems a spook which can never be exorcised from man's imagination. Quite recently Arndt has deduced from experiments, to which I shall presently refer, a con- clusion which may be regarded as modified spontaneous generation ; namely, that certain elements of animal- cells can, under favoring conditions, continue to exist and develop into bacteria after the death of the cells of which they were previously constituent molecules. Yet the evi- dence adduced does not as yet warrant any hesitation in accepting the current doctrine that bacteria, like all other organisms, proceed from pre-existent similar beings. In order to discuss intelligibly the individual bacteria, we must agree upon a classification. The nomenclature has given rise to much discussion and more confusion. At first each investigator christened, after his own fancy, every new variety. The French school, first in the field by virtue of Pasteur's work on fermentation, em- ployed, very loosely, the terms vibrios, monads, toru- lacese, etc. Natural selection has proven Cohn's classi- fication the fittest to survive, which is quite natural, since the greater part of our exact knowledge of this sub- ject is due to this distinguished botanist and his pupils. Cohn's original classification permits and will doubtless need amendments ; in fact, he has already proposed some essential modifications based chiefly upon the form and mode of association of the individual cells. I shall adhere to that nomenclature in general use by the Ger- man mycologists. Bacteria are distinguished in this system according to form simply into (i) micrococci, or spherical bacteria ; (2) oblong bacteria, or simply bacteria ; (3) bacilli, or rod bac- teria ; (4) spirilla, or spiral bacteria. A disadvantage in this nomenclature is the employment of the word bacte- ria to designate two different conceptions the entire tribe including all four classes, a general name, and the second class oblong bacteria (Figs, i, 5), in distinction from the others a double signification which has led to Fig. i. Various bacterial forms. i. Microcoocus septicus ; n- vestigation of bacteria improvements which confer such evident and extreme advantages that they have become absolute necessities for original research in this field ; in- deed so many errors of commission, as well as of omission, have been thereby detected in other methods, that one is 39 disposed to regard as uncertain any researches in which these measures most essential to accuracy of observation are neglected. Having demonstrated the life history of the bacillus anthracis, which the French school, working with Pasteur's clumsy method, had for sixteen years failed to discover, Koch turned his attention to the etiology of surgical infectious diseases. He found that the subcu- taneous injection into a mouse of five drops of putrid blood was followed by immediate prostration, and in four to eight hours by the death of the animal. Th&re oc- curred in these cases no local reaction, the internal or- gans were apparently normal, no bacteria were detected in the blood or tissues, inoculation of other animals with the blood from the heart caused no perceptible effect. Koch considers this disease therefore as septicaemia, etymo- logically as well as clinically the introduction into the blood of a poisonous substance, soluble, not reprodu- cing itself, analogous, in fact, with the effect of certain vegetable alkaloids and of ptomain, the substance iso- lated by Selmi from human corpses, which so closely re- sembles atropine in its physiological effects. This is also the effect obtained from the injection of boiled pu- trid materials by Panum, Bergmann and Schmiedeberg, and others. Koch found, however, that the injection of a smaller quantity, one-half to one drop of the same pu- trid blood, was followed by entirely different effects. In some cases the mouse was apparently unaffected ; in others brief, transient depression was observed ; in per- haps one-third of the cases there ensued, twenty-four hours later, progressive weakness, retardation of respira- tion, drowsiness, and, in forty to sixty hours, death. Sec- tion revealed no other pathological changes than local redema at site of inoculation and decided enlargement of the spleen ; but after inoculation of a second mouse with a minute quantity (one-tenth to one-half drop) of liquid from this oedema, or of blood from the heart, the latter animal presented, in forty to sixty hours, precisely the same clinical and pathological picture as the first ; from the second, a third was successfully inoculated, and 40 so on ad libitum ; indeed, the mere contact with a fresh wound of a scalpel-point previously dipped in the septic blood sufficed. Here, then, was something entirely dif- ferent from the intoxication following injection of a larger quantity (five to ten drops) differing in the existence of a marked stage of incubation, of local reaction, and in certain and uniform infectiousness. The blood of such an animal evidently contained something not present in that of the former mouse a something requiring time for the manifestation of its influence, and finally distributing itself throughout the entire blood-mass, so that each drop thereof possessed the septic possibilities of the original putrid drop. Such mode of action implies reproduction, and reproduction is a characteristic of organized matter. It was to be expected a priori, therefore, that the blood contained organisms ; Koch found, in fact, invariably, that the blood serum, white blood-corpuscles, and various tissues of such animals swarmed with minute rods, which stained readily with aniline colors, and when removed from the body into similar artificial conditions multi- plied by transverse fission. Since the blood of the in- fected and infecting mouse differs evidently from that of the intoxicated and non-infecting mouse only in the presence of these bacteria, Koch ascribes the infectious- ness to these organisms. It is interesting to note that all attempts to inoculate rabbits and field-mice with the septic blood were fruitless. The animals remained unaffected ; no bacilli were found in their blood, al- though the mouse-blood used for inoculation was full of them. Further, that although the putrid fluids in- jected contained organisms of numerous varieties micro- cocci, bacteria, bacilli all of which were subsequently found in the local oedematous liquid, yet only one spe- cies, the minute bacillus, was found distributed through- out the blood and tissues. The living mouse seemed to be a culture-medium for isolating these from the other va- rieties, to whose growth the animal's tissues were less perfectly adapted. In the second or third mouse suc- cessively inoculated only the specific bacilli were found. 41 By methods essentially similar, Koch demonstrated the association of another form of septic infection of mice, with a micrococcus species ; of septicaemia in rabbits with a bacterium ; and of pyaemia (with me- tastatic abscesses) in the latter animal with a micro- coccus variety. Yet, although the fact of association was amply demonstrated, there still remained the pos- sibility of objection that the essential agent in the in- fection was a soluble, unorgani/ed substance contained in the putrid liquids and the infectious tissues used for inoculation, the bacteria being the result and not the cause. The final demonstration to the contrary, the proof that these different effects could be induced by inoculation with the respective bacterial varieties after complete isolation from accompanying animal tissues by cultivation upon solids, was not furnished at the time of this publication by Koch, but has been subsequently com- pletely established by Koch, Gaftky, and Loffler in the laboratory of the German Health Bureau, for the bacilli of mouse- and the bacteria of rabbit-septicaemia. The extreme accuracy and critical supervision of manipula- tions, the logical sequence of methods, and withal the unpartisan candor and earnest desire for truth evident throughout this work of Koch's, inspired at once a confi- dence which has not as yet been diminished nor betrayed. It is worthy of note that the infectious disease of mice de- scribed by Koch as malignant oedema is identical in clin- ical and pathological appearances with that which Pas- teur ascribes to his " vibrio septique ; " while the pyaemia of rabbits corresponds accurately with the purulent infec- tion which, according to Pasteur, follows the injection of his microbe of pus. These results, obtained quite inde- pendently by two observers, using different methods, have been confirmed not only by Gaffky and Loffler, but also by Rosenberger in Wiirzburg, in a series of carefully per- formed experiments. A review of the evidence already considered shows, then, that infectious diseases, identical in clinical and anatomical appearances with the various forms denom- 42 inated septicaemia in man, have been induced in the mouse and rabbit by inoculation with animal tissues in various stages of putrefaction ; that the resulting infection is just as certain if the putrid substances be previously boiled and thereby deprived of living organisms (Pammi, Bergmann, Rosenberger). On the other hand, it is cer- tain that per se innocuous culture fluids infusions of beef, etc. acquire, after inoculation with minute quan- tities of infected blood or tissue, the same septic proper- ties, provided such blood or tissue contain living bac- teria ; it is further certain that this multiplication of the septic substance in such liquid is a concomitant of the vital action of the organisms therein contained (Pasteur, Koch, Rosenberger) ; it is further demonstrated that these organisms can and do, not alone multiply the sep- tic material, but when isolated by successive cultures from all the accompanying animal tissues, induce, inde- pendently, fatal infectious disease (Pasteur, Koch, Luf- fler, Gaffky, Rosenberger). The same principle vital activity of bacteria per- vades all these phenomena ; for the artificial induction of septic diseases has been, in all these experiments, origin- ally accomplished by the incorporation into the animal of putrid tissues, with or without bacteria. Now, since putrefaction must be regarded, in the present state of our knowledge, as impossible without the presence of these organisms, it is evident that sepsis, putrid infection, was in every case due, directly or indirectly, to the action of bacteria ; since even the boiled substances used by Panum and Rosenberger, and the sepsin obtained from rotten yeast by Bergmann and Schmiedeberg, had ac- quired their septic properties through putrefaction, i.e., through the action of bacteria. Hence we are logically driven, by all this work, to the belief that septicaemia im- plies, the introduction into the animal either of living bac- teria, or of a substance which has acquired noxious prop- erties through previous vital activity of these organisms. More recent experiments have demonstrated, however, that the etiology of the group of clinical and anatomical 43 appearances known as septicaemia is by no means re- stricted to putrid infection. In the researches as to the nature of blood coagulation, instituted by Schmidt, of Dorpat, and his pupils, it was noticed incidentally that the introduction or production in the blood of fibrin-fer- ment in considerable quantity produces effects identical with those of putrid infection septicaemia. In this case the result is of course attributable to coagulation of the blood. Similar phenomena were observed by Kohler, Angerer, Naunyn, and Francken, to follow intra-venous injection of fresh blood-serum (containing therefore both fibrinoplastin and ferment) , of haemoglobin solution (which is known to favor the formation of fibrin-ferment in the blood) ; of sulphuric ether (which sets free haemo- globin and hence indirectly fibrin-ferment). Injected in large quantities, these substances caused immediate death by instant coagulation of the blood in the heart and large arteries ; after smaller quantities the animals survived hours or days, and exhibited the usual symptoms of septi- caemia ; their blood contained free fibrin- ferment, while that of healthy animals does not. Finally Edelberg, working under Schmidt's direction, established clearly that the injection of fibrin-ferment alone, isolated from other ingredients of blood, can induce the same phe- nomena. In a series of experiments communicated to the Con- gress of German Surgeons, in 1882, Bergmann observed the clinical and anatomical features of septicaemia fever, swelling of spleen and lymph-glands, gastro-intestinal inflammation, cardiac weakness, ecchymoses in mucous and serous membranes after the injection of the physi- ological ferments, pepsin and trypsin. in small doses ; large quantities induced, like fibrin-ferment, immediate death by coagulation of blood in the larger vessels. Raynaud and Lannelongue inoculated rabbits with saliva from a child dead of rabies, and induced thereby an infectious disease, terminating fatally in forty-eight hours or less. Pasteur found in the blood of these animals a bacterium which he regarded as the cause of the disease. 44 Inoculation of rabbits with saliva from children dead of broncho-pneumonia caused the same result, and pro- duced the same figure-of-8 bacterium. The same or- ganism was found in the saliva of a healthy adult. Stern- berg found that injection of fresh saliva from certain healthy individuals caused a similar fatal infectious dis- ease, which he calls septicaemia, in rabbits, characterized by the presence of a micrococcus apparently identical with Pasteur's ; and asserts that this organism, isolated by flask cultures, induced the disease again upon subcu- taneous inoculation. Neucki and Gautier isolated from saliva a substance capable also of producing fatal infec- tion of certain animals. Saliva, then, not only after death of the subject, but even fresh from the living individual, can also induce septicaemia. Whether the effect shall be ascribed to a contained bacterium or not is immaterial to our present purpose, which is to emphasize the fact that the group of phenomena called in general septi- caemia may follow other causes than putrid infection ; may be induced on the one hand by the vital action of isolated bacteria, and on the other by unorganized sub- stances the boiled septic materials of Panum and Rosen- berg, the sepsin of Bergmann, the fibrin-ferment of Edel- berg, pepsin and trypsin of Bergmann, haemoglobin, etc. The mode of action common to several, at least, ap- pears to be the liberation of fibrin ferment ; for the blood of septicaemic animals is characterized by the presence of free ferment, which is not found, unless perhaps as traces, in normal blood. This ferment seems to arise, according to the researches of Schmidt, in the disinte- gration of white blood-corpuscles ; and these are known to be invaded and apparently disintegrated by bacteria, in the septicaemia of mice and rabbits, at least. It would appear, although not for all cases demonstrated, that the clinical and anatomical features common to the various forms of septicaemia are attributable to the rapid libera- tion of fibrin ferment in the blood ; and that any agent organized or unorganized, putrid or fresh capable of effecting such liberation may induce the disease. This conception, at any rate, enables us to understand much that is otherwise perplexing. Various have been the attempts, for example, to explain the so-called asep- tic wound fever, which occurs in the majority of severer wounds, even under the most perfect Lister dressing. Kiister and Sonnenburg ascribed it to absorption of car- bolic acid ; but extensive experiments upon man, as well as the lower animals, have proven that the acid does not cause fever ; but .induces, on the contrary, after slight, brief, and by no means constant elevation, a decided depression of temperature. Others have referred the phenomenon to absorption of chloroform a hypothesis incompatible with the fact that wound fever follows op- erations performed without anaesthesia (as is so often done in Germany and Austria) as usually as those done under chloroform. The more general opinion, that aseptic wound fever differs from sepsis, i.e., putrid infec- tion in degree rather than in kind, meets a serious ob- fection, as Gussenbauer remarks, in the fact that the jormer occurs within a few hours after the infliction of the wound, before decomposition and consequent sepsis can be reasonably presumed to have occurred. The clinical facts (i) that a large minority of wounds, severe as well as slight, are followed by no fever under the Lister dressing, as was the case in over three hun-' dred of a thousand reported by Volkmann and Genz- mer, and in nine of twenty-four most carefully observed by Edelberg ; (2) that the course of subcutaneous frac- tures without extravasation of blood is usually afebrile, while similar fractures with extensive blood extravasa- tion often induce fever ; (3) that the application of a tight bandage to a wound or fracture, which must cause some extravasation of blood, is often followed by fever in a patient previously afebrile (Edelberg) ; (4) that the blood of patients during simple surgical fever sometimes contains free fibrin ferment in appreciable quantities such facts indicate that aseptic wound fever is caused by absorption from extravasated blood, especially since it has been demonstrated, as already remarked, that .46 blood, fluid or coagulated, haemoglobin, or even isolated fibrin ferment can experimentally induce the same phe- nomena. It is further conceivable, though not demon- strated, that the products of a local inflammation, or the modification of cell-activity through fatigue or emotion, may also be directly responsible, through destruction of leucocytes and liberation of fibrin ferment, for some of those cases of spontaneous septicaemia which we ordi- narily ascribe to unperceived entrance of bacteria or putrid products into the body. Septicaemia is, then, a collective name for processes more or less similar, but etiologically distinct at least, in certain lower animals ; any one of several unorgan- ized substances, any one of several bacteria (at least, three in the case of the mouse) may induce character- istic symptoms. It has been proposed to adopt the term sapr&mia for putrid infection without bacteria, re- taining the usual name to indicate the effect of organized agents; yet the clinical distinction is probably rarely possible. The clinical experience of all ages has unanimously ascribed the second type of septic infection character- ized by chills, a remittent or intermittent fever and the formation of multiple abscesses to absorption from pus ; and it has always been designated by a name pyaemia, purulent infection indicative of this supposed origin. The discussion of the relations of bacteria to pyaemia begins, therefore, naturally with the consideration of their relations to suppuration. That these organisms should exist in pus exposed to the air, as in other albuminous liquids under like conditions, was a priori probable and long ago demonstrated ; that they exist also in the pus of abscesses which have never been opened, has been conclusively demonstrated by Klebs, Nepven, Rind- fleisch, Waldeyer, Cheyne, Ehrlich, and especially by Ogston, who found micrococci in every one of seventy previously unopened acute abscesses, though rarely in chronic, cold abscesses. The mere fact of association does not, of course, ne- 47 cessarily prove a causal relation of the organisms to the suppurative process ; but the observation that a zooglcea mass of micrococci is often the centre of an abscess ; that indeed abscess-formation in all staged, from a simple accumulation of straggling leucocytes to the fully devel- oped destructive infiltration of tissue, has been observed Fig. 6. Incipient abscess formation around an embolus of micrococci ; heart muscle in a case of endocarditis ulcerosa. X 100. (Copied from a photogram by Koch.) around a nucleus consisting of a minute embolus com- posed entirely of micrococci (Fig. 6) ; that the progres- sive purulent infiltration of the surrounding tissue is pre- ceded by an invasion of the same by micrococci can be impartially and satisfactorily explained, in the present state of knowledge, by no other hypothesis than that 48 the micrococci cause the suppuration. Experimentally there is direct evidence to the same effect. Pasteur saw, after cultivation of a micrococcus found in ordinary water, that the injection of a few drops of the previously harmless culture-fluid, now containing myriads of micrococci, was invariably followed, in the rabbit, by suppuration around the point of injection, the pus and tissues containing numbers of the same organ- isms. The intr a- jugular injection of the same fluid caused multiple abscesses in the internal organs. He found the same micrococcus in pus from cases of puerperal fever. Klebs, Zahn, and Tiegel found that while the injection of pus from a py?emic abscess or putrid fluid was followed by local suppuration and multiple abscess formation in the infected animal, the same pus or liquid, after nitra- tion through clay cylinders whereby the bacteria were separated from the liquid caused intense general infec- tion, but no suppuration, even at the point of injection. Koch observed also the constant association of a charac- teristic micrococcus with infectious suppuration in the rabbit after putrid inoculation. It appears, therefore, impossible to evade the conclu- ion that suppuration can be and is induced by micro- cocci. That this effect is induced by one or more specific varieties of these organisms seems probable from these researches of Klebs, Koch, and Pasteur ; that it is not induced by all species is apparent from the fact that colonies of micrococci are frequently present in the human and other animals during various morbid pro- cesses in which suppuration does not occur as in erysipelas. As to the mode in which this influence is ex- erted, there is no definite knowledge ; the assumption that the deleterious effect results from changes in the chemical constitution of the containing medium, as an essential feature of the vital activity of these organisms, is supported by analogy with the processes of fermenta- tion and putrefaction, by the phenomena known to at- tend the life of other bacteria, and by the direct observa- tions of Koch and Pasteur. 49 Yet the induction of suppuration is not a monopoly of micrococci : the growth of the actinomyces bovis in the tissues is accompanied by the formation of abscesses ; upon microscopic section the fungus is found constitut- ing the nucleus of a miliary abscess ; and inoculation with the isolated actinomycetes proves that the fungus itself, and not a hypothetical soluble substance accom- panying it, is responsible for the suppuration. Experi- mental researches upon suppurative keratitis by Leber, of Gottingen, make it highly probable that another bac- Fig. 7. Actinomyces bovis tongue of ox. X 140. terium, the leptothrix of the mouth, and a mould fungus, aspergillus glaucus, can also induce suppuration. On the other hand, several bacterial varieties are known to inhabit at times human and other animals without caus- ing suppuration the bacillus anthracis, for example. The school of pathologists of which Weigert is a prominent exponent, has been inclined to regard micro- organisms not merely as a cause, but as the sole cause of acute suppuration. This view was certainly incom- patible with many clinical observations, and has been 3 50 recently quite dissipated by experimental research. Uskoff, under Ponfick's direction, has shown that the subcutaneous injection into rabbits of turpentine oil, is followed by the formation of pus in which no bacteria can be detected ; an assertion which has since been cor- roborated by others. The most accurate and conclusive Fig. 8. Actinomyces bovis, and pus corpuscles. X 260. experiments in this direction were recently made by Dr. Wm. T. Councilman, of Baltimore, in the laboratory and under the direction of Cohnheim. Councilman made a number of glass capsules, heated them to redness, poured into each, while still hot, a boiling mixture of croton and olive oil, and sealed the open end in the flame. Four- teen of these were inserted, with antiseptic precautions, under the skin, at various places, in different rabbits. In no instance was suppuration or even adhesive. inflamma- tion observed the capsules remained freely movable in the subcutaneous tissue. After intervals varying from two to fourteen days, when the incision wound was firmly healed, the capsules were broken subcutaneously, by force applied to the skin ; in every instance suppuration followed in a few hours. An examination of the pus and abscess walls revealed nothing that could be recognized as bacteria. Chronic or cold abscesses may have a different etiol- ogy their clinical history and appearances, and the fact that they seldom cause pyaemia, would point to that con- clusion. It is significant that of eighteen chronic ab- scesses, Ogston employing the most approved tech- nique could detect bacteria in but four, which were consequent, moreover, upon erysipelas, typhoid fever, pharyngitis, and pulmonary consumption, respectively ; in the remaining fourteen, both microscope and attempts at cultivation gave only negative results. Their absence at the time of examination does not exclude the possi- bility of their presence at an earlier period of the pro- cess ; that they may have lost their vitality, and with it their power to absorb the coloring agents. Suppuration must be regarded, then, as indicating the presence of an element foreign to the living animal cells ; which may be introduced directly, like the croton oil in Councilman's experiment, or indirectly as an incident in the life of various fungi. That a derangement, of cell- nutrition, local gangrene, may by mechanical or chem- ical irritation, without the presence of other organisms, effect the same result, seems probable in view of clinical experience, but is not yet experimentally proven. Prac- tically, we may regard acute suppuration as proof of the access of external irritant matter, organized or unorgan- ized ; and clinically, we must agree with Cohnheim, that suppuration not due to bacteria or other fungi is ex- tremely rare. The comparative rarity of pus-formation under the Lister dressing although this is, at best, an 52 uncertain means of excluding organisms is highly sig- nificant of the relations between the two. That form of septic infection known as pyaemia is dis- tinguished by abscess formation in external organs from which fact alone it is evident that bacteria must play an essential part in the disease. Yet there is abundant direct evidence to the same effect : these metastatic abscesses always contain bacteria ; these organisms exist not simply in the pus and in the inflamed tissue constitu- ting the abscess wall, but also in a zone external to the territory already involved in inflammation ; the invasion by organisms may therefore apparently precede the in- flammatory re-action ; further, incipient inflammation and suppuration are observed around minute emboli consisting of micrococci ; and finally, although throm- bosis and embolism occur in various pathological condi- tions, no suppuration occurs in such fibrinous masses, nor in the adjacent tissues, unless bacteria also be present. These anatomical facts are quite in accord with the inde- pendent evidence of experimental research. Panum found that the injection into the jugular vein of minute balls of wax or mercury caused the formation of emboli in the lungs, but that no suppuration occurred around them ; he then combined embolic formation with putrid infection by the injection of putrid fluids just before or just after the formation of efhiboli, through the incorpora- tion of wax, mercury fibrin or cheese particles ; and varied the experiment by the artificial induction of superficial phlegmonous inflammation, in the course of which the formation of emboli was secured by injections as before. The result was always the production of simple, non-sup purating embolic masses ; the substitution of fresh blood- clots for the wax, mercury, etc., whereby a closer approxi- mation to the natural embolic process was secured, gave the same results. Emboli caused by intra-venous injec- tion of particles of putrid flesh, however, were promptly followed by suppuration. Other experimental researches into the formation of embolic (metastatic) abscesses by Virchow, Billroth, Weber, Waldeyer, Cohnheim 53 confirmed these results of Panum ; putrid emboli always softened and excited suppuration ; others rarely ; it was further established (Waldeyer) that puriform softening of a thrombus can be caused by contact of pus or putrid matters with the external surface of the containing vessel, as well as by admission to its lumen. Since suppuration in the immediate vicinity "of a vein may cause inflamma- tion and thrombus formation in the vessel, it is apparent that phlebitis, puriform softening of thrombi in short, pyaemia may occur without any artificial solution of continuity in the vascular walls. Experiment has always shown that fluids (pus and putrid matter) capable of in- ducing pyaemia, lose by boiling (Panum, Bergmann, Pas- teur) or by filtration (Klebs, Zahn, Tiegel) this power to cause metallic suppuration pyaemia though still able to induce rapid and fatal infection septicaemia. Since by these measures boiling and filtration the contained organisms are destroyed or eliminated, experimenters are unanimous in ascribing the induction of metastatic ab- scesses to bacteria. The clinical evidence is almost as strong ; for, accord- ing to the unanimous assertions of eminent surgeons Nussbaum, Volkmann, Esmarch, Thiersch, Verneuil, Schede, Gussenbauer, for example pyaemia is practic- ally unknown after wounds which have been treated from their inception by the Lister method, the avowed object and essential feature of which is the attempt to exclude organisms. Perhaps the strongest clinical evidence of the septic influence of bacteria is afforded by the cases of so-called spontaneous pyaemia, where no suppuration nor solu- tion of continuity is detected. In many of these a closer search would doubtless reveal a possible source of puru- lent infection. Weichselbaum has recently called attention to fatal cases of this kind in which the focus of infection was found as suppuration in the nose and antrum. Yet there still remain numerous cases in which pyaemia ap- pears to proceed from deeply situated abscesses, which can have had no direct communication with the external world 54 after subcutaneous fractures, for example ; and still another class in which a general infection without local suppuration during the first few days occurs without ex- citing cause, unless perhaps exposure to cold ; and until the appearance of pus in the joints, etc., cannot be dis- tinguished from acute rheumatism or from other infec- tious diseases. To this category belong cases of acute osteomyelitis and ulcerous endocarditis. The blood and metastatic abscesses contain in these cases also the usual micrococci ; the history presents, in fact, nothing unusual except the obscurity of the infection. In some of these as in one of osteomyelitis reported by Gussen- bauer the bacteria were observed in the blood and in the bone-marrow before suppuration had occurred ; the general infection preceded the local affection. Such cases must incline us decidedly to the view that the mi- crococci caused not only the local suppuration, but also the primary general infection. It is noteworthy that such cases of primary pyaemia often follow exposure to cold ; perhaps we should regard the retention of certain material in the blood, this interference in excretion, as a predisposing moment which has favored the develop- ment of organisms; diabetic patients^ certainly are espe- cially prone to local gangrene and septic infection after a wound, and it is equally well known that a minute in- cision, even needle-puncture of the dropsical skin in amyloid degeneration of the kidney, exposes the patient to erysipelas and pyaemia. Yet in some cases the bacteria essential to pyaemia can and do exhibit their vital activ- ity in the human body without the pre-existence of any recognizable deviation from the usual health, and with- out any discoverable solution of continuity in the integu- ments. In this discussion I have assumed the etiological iden- tity of the septicaemia and pyaemia of man with that of processes marked by the same clinical and anatomical features in animals. To such assumption objection may be made, based on the known differences in the effects produced on man and other animals by the same toxic 55 agent ; rabbits, for instance, live and fatten on a diet of belladonna leaves, and carnivorous animals are but slightly susceptible to anthrax. But when we consider that the septic processes of man are objectively identical with those of other animals, that they result in various animals alike from putrid and purulent infection, and furthermore, that they have been induced in animals by direct inoculation from the human subject, we must jus- tify the application to man of the principles ascertained from the study of these septic diseases in other animals. Although our present knowledge of the etiology of septic infection is thus incomplete, our ability to pre- vent such infection is fortunately more satisfactory. For we may practically classify all such cases into two cat- egories those in which a possible source of infection is previously apparent, and those in which no such source is discoverable. The treatment of the former class, the large majority, comprising all wounds, I may be permitted to discuss in so far as the principles of such treatment are based upon a recognition of the agency of bacteria in the morbid processes. Septic infection from a wound means the absorption through that wound of one or more constituents of the putrefactive process. Now, putrefaction is impossible without bacteria ; hence septic infection implies the vital activity of bacteria, past or present. The actual presence of bacteria in the wound is, as has been shown by Panum, Bergmann, and others, unnecessary septicaemia may be induced by putrid liquids deprived of bacteria ; but these liquids are putrid they embody the products of bacterial life. Pre- caution against the introduction into a wound of already formed poisons by disinfection of hands, instruments, sponges, etc., on the side of the surgeon, and by similar cleanliness as to the body of the patient, is evidently the first measure against sepsis a measure quite overlooked occasionally by surgeons who intend to use all so-called antiseptic precautions. I once saw a laparotomy made by a rigid apostle of Listerism ; the carbolic spray was used ; hands, instruments, ligatures, etc., thoroughly car- 56 bolized ; but the patient's skin was not even washed ; several coils of intestine were in course of the operation laid upon the skin, and came in contact with the pubic hair. The operation itself was not formidable, but the woman died of purulent peritonitis. If no infectious matter be thus carelessly introduced from without, the occurrence of sepsis from a wound necessarily implies decomposition in the wound itself. For the accomplishment of such decomposition it is evi- dent that three factors must concur : i, the presence of animal tissues deprived of vitality, and hence capable of putrefaction ; 2, the presence of organisms capable of inducing putrefaction ; 3, the prevalence of conditions which permit the vital activity of these organisms. The absence of any one of these conditions renders putrid infection impossible. We are familiar with analogous phenomena outside of the body. Urine or blood in free contact with ordinary air putrefies ; if access of bacteria be prevented by closing the mouth of the test-tube with cotton, etc., putrefaction does not occur ; the process can be prevented with equal certainty by changing the environment addition of alcohol for example whereby the vital activity of bacteria is arrested. We have abun- dant evidence, as has been already stated, that the same principles prevail within as well as without the living animal. That the bacteria ordinarily present in the air are powerless to destroy living tissues is proven by the fact that un filtered ordinary air has been passed for hours through the peritoneal cavity of rabbits without inducing pathological changes indeed, the entire subcutaneous tissue of animals has been inflated with air with like re- sult ; by the harmlessness of surgical emphysema ; by Miller's injection of such bacteria into his own body, etc. That the presence of putrefiable substances, if excluded from these same bacteria, gives rise to no putrefaction nor sepsis is shown in the cases of intra- and extra-uterine pre- gnancy, where a dead foetus is carried for months or years. The prevention of decomposition and consequent septic infection from a wound can therefore be accom- 57 '&- plished theoretically in any one of three ways : i, the exclusion of putrefiable materials, i.e., cleanliness; 2, the exclusion of bacteria ; 3, the addition of a substance in whose presence putrefactive bacteria are inert. It is evident that the accomplishment of any one of these three ends is antiseptic, or, if you prefer on ety- mological grounds, aseptic surgery. There is a preva- lent inclination to consider Listerism and antiseptic surgery as synonymous terms ; and to regard the success in avoiding sepsis which is secured by other methods the open air and simple water dressing, for example as proof not only that the Listerian details are unneces- sary, but also that the agency of bacteria in the induction of sepsis an agency which the Lister method was de- vised to defeat is a myth, a mere craze, a fashion. It is manifest, however, that antiseptic surgery is far more comprehensive than Listerism. Listerism aims chiefly at but one of the three possible ways for the prevention of sepsis the exclusion of ferments ; the very methods whose success has been considered proof of the fallacy of antiseptic surgery demonstrate practically what is self-evident theoretically, that putrefaction and putrid infection from a wound can be prevented by the removal of putrefiable materials, just as certainly as by the ex- clusion of organisms. The aseptic success of Savory and Lawson Tait rivalling that of Volkmann, Esmarch, and Lister, was secured by the most scrupulous care in avoiding the retention or accumulation of any discharge in the wound. The result is asepsis, the means aseptic. That this method of preventing sepsis affords the same certainty of success and possesses the same range of ap- plicability as the Listerian, I would not maintain ; in- deed, my own limited experience, including some obser- vation of surgery in St. Bartholomew's Hospital, inclines me to the contrary belief. I would merely protest against the not infrequent assertion that Savory's and Tait's success in avoiding putrid infection is an argument against the demonstrated agency of bacteria in the in- duction of sepsis. 3* 53 There still remain a considerable number of cases, notably wounds of mucous membranes, in which ana- tomical relations prevent the execution of either of these aseptic methods : bacteria cannot be excluded, nor per- fect cleanliness of the wound secured. In such cases asepsis can be theoretically obtained very simply by the presence of some substance in the wound which renders vital activity of bacteria impossible. There is a great variety of such agents alcohol, carbolic acid, etc. but for these cases all such are, from their volatility or solubility, practically useless ; and it was reluctantly ad- mitted on all sides that operation wounds involving mu- cous membranes could not, generally speaking, be ren- dered aseptic with certainty. Between 1860 and 1880 Billroth performed the amputation or extirpation of the tongue one hundred and nineteen times on one hundred different individuals ; and notwithstanding the most care- ful attention, including frequent syringing with solutions of potassium permanganate, carbolic acid, or other anti- septic, twenty-six of these patients died, nearly all from septic infection, either directly from the wound or in- directly through the inhalation of septic products " schluckpneumonie." With the introduction of iodo- form into surgery the long-sought substance was found comparatively insoluble and non-volatile in whose presence the ordinary bacteria do not multiply. Under the proper use of iodoform wounds of mucous membranes are as secure from decomposition and septic infection as an amputated stump under a Lister dressing. This is admitted even by the fiercest opponents of iodoform those who, like Kocher of Bern, having ignorantly poi- soned their patients with it, would transfer to the agent *he odium which evidently belongs to themselves. In 1 880-8 1 Billroth made eighteen tongue extirpations, packing the wound with iodoform gauze which was al- lowed to remain undisturbed five to seven days, then sometimes renewed. Not a single septic infection oc- curred ; recovery followed in every instance. An operation which, though not per se formidable, 59 had, even in Billroth's skilful hands, been followed by a greater mortality than that attending ovariotomy, was de- prived of its septic terrors. I would particularly recom- mend this to the consideration of those who ignore all experimental work, who admit as worthy of considera- tion only clinical results, and who regard the success of Savory and Tait as the overthrow of aseptic surgery in particular, and of bacteria in general. Here is aseptic surgery par excellence, though the spray, protective, mackintosh, and attendant paraphernalia are absent ; here is the prevention of septic infection by measures which do not exclude bacteria from the wound, but sim- ply restrain their development. The method of Lister, conceived and devised upon a hypothesis, before the as- sumptions of that hypothesis had been verified, con- tained, as subsequent developments demonstrated, some errors of conception and execution. The spray, for example, that sign-manual of Listerism in the pro- fessional mind, seems less essential since we have learned that bacteria are less numerous in the atmos- phere than was formerly supposed ; and when we con- sider the researches published by the German Health Bureau, it seems somewhat doubtful whether the carbolic acid spray ever killed a single healthy bacterium ; the vitality of certain spores is certainly not thereby affected. Koch found that the spores of anthrax bacilli, for exam- ple, retained their power of development after immersion for seven days in a two per cent., and after twenty-four hours in a five per cent, solution of carbolic acid ; yet the bacilli lost their vitality after two minutes' contact with even a one per cent, solution. The clinical results also support the assertion that irrigation of the wound accomplishes quite as effectually the object for which the spray was designed. Yet it must be admitted that ex- cept in those cases, such as abdominal sections, where the spray causes positive and decided injury, there is a possibility of benefit from its use. For application to the wound, many substitutes have been proposed for the objectionable carbolic acid ; 6o Fischer employs naphthalin ; Schede and others report excellent results from corrosive sublimate ; Langenbeck and Billroth regard iodoform as satisfactory. To secure cleanliness freedom of the wound from all putrefiable materials surgeons now more generally ap- preciate the importance of ligating or twisting every ves- sel, however small, which could bleed when, with the discontinuance of the anaesthetic, the heart's impulse be- comes stronger. The application of a firm, even, elastic bandage over the lips of the wound is often used, also, to accomplish the same object. For absorption of pu- trefiable materials Esmarch has used with great satisfac- tion turf enclosed in gauze bags ; Schede is pleased with sand, previously heated and soaked in corrosive subli- mate solution, which is poured directly into the wound. Perhaps one of the most important of antiseptic measures is the deep closure of the wound ; whenever the lips of the wound are thick as in abdominal sections and thigh amputations the use of silver wire and lead plates for approximation of the deeper surfaces is essential to pre- vent the accumulation of blood in the pockets otherwise present, and the consequent danger of sepsis. Antiseptic surgery, then, is not comprised in the spray and carbolic acid ; it is not simply a question as. to the relative anti-bacterial properties of this, that, and the other so-called antiseptic agents. It is an attempt to prevent the entrance into, as well as the formation within, a wound of all substances, organized and unor- ganized, which can interfere with cell-nutrition. It com- prises, first, the exclusion or removal of all putrefiable materials blood, pus, necrosed tissue (a point to which the Listerian school seems inclined to ascribe a subordi- nate place; witness Cheyne's "Antiseptic Surgery"); second, the exclusion of all ferments, bacterial or other ; and, since neither of these can always be accomplished, since even under the most perfect Lister or other dress- ing, both putrefiable materials and bacteria may be present ; third, the establishment of conditions incompat- ible with bacterial development. The most complete 6i antisepsis is evidently not that which sees in bacteria the sum and substance of all surgical evil, but that which rec- ognizes and endeavors to avoid all possible sources of infection. The most perfect realization of this ideal which it has been my fortune to witness is seen, not in King's College Hospital, but in Billroth's clinic. Sponges are prepared by the abstraction of fat and sand, and by at least fourteen days' immersion in five per cent, carbolic acid solution, in which they remain until used ; for the operation they are put in two per cent, solution ; ligatures (Billroth generally uses silk) are also kept in a similar solution. The skin at and around the location of the proposed incision is shaven, scrubbed with a flesh- brush and soap, and washed with carbolized water ; hands and instruments are most scrupulously cleansed ; operator and assistants wear clean linen dusters ; no spray is used. Every bleeding point, however small, is caught temporarily in a clamp forceps, and at the close of the operation, ligated at the end of the severed vessel, to diminish the amount of necrotic tissue ; the surface is thoroughly irrigated with three per cent, carbolic solu- tion ; a little powdered iodoform is often dusted into the wound not, however, if immediate union be expected. If the soft parts severed be thick, the lips of the wound are approximated deeply by silver wires, and superficially by closely set silk sutures. The Esmarch bandage is re- moved from the limb in amputations as late as possi- ble, since absorption does not occur so long as the ban- dage remains, but begins very actively so soon as the circulation is restored. A strip of iodoform gauze, usu- ally also some powdered iodoform, is applied to the seam ; then several layers of iodoformed or carbolized gauze ; finally a very firm roller, starched organdine, or even elastic bandage is tightly applied over the lips of the wound. The first dressing remains unmolested as long as possible, the time varying, of course, with the case. LECTURE III. IN 1879 Neisser made the assertion, based upon nu- merous examinations, that there is present in the purulent discharge of gonorrhoea, whether from urethra, vagina, or conjunctiva, a micrococcus not found in other pus, distinguished by its size, shape, and mode of repro- duction. Neisser's previous work entitled this assertion to respectful consideration, and it was at once subjected to extensive tests. The reports have been, with one ex- ception, unanimous in corroborating Neisser's assertion in all its details. I may mention especially Ehrlich, a most expert and experienced, yet conservative and trust- worthy observer ; Gaffky, a pupil and present assistant of Koch ; Aufrecht, of Magdeburg ; Loffler, Leistikow, Bockhart, Krause ; and among the ophthalmologists, Leber, Sattler, and Hirschberg. The only dissenter, so far as I know, is Dr. Sternberg, who asserts that this micrococcus form is widely distributed, and is, in fact, the same as that which Pasteur has shown to cause fer- mentation of urea. Several attempts have been made to inoculate human subjects since animals are not susceptible to the con- tagion with the isolated micrococci. Bokai, in Pesth, asserts the induction of urethral gonorrhoea in three out of six students so inoculated ; but as he neglected to keep them in solitary confinement during the trial, the experiment is not so convincing as it might be. Bock- hart, having cultivated the organisms on gelatine, in- oculated with the fourth culture a paralytic hospital pa- tient, and observed a typical gonorrhoea on the sixth day. Sternberg cultivated micrococci from gonorrhceal pus in flasks, and observed only negative results in each of five patients inoculated therewith. Thus far, therefore, it is not decisively established that the bacterium associated with gonorrhoea is the cause of the disease. Dr. Stern- 63 berg's present experiments, like all his previous work, evince great care, skill, and a sincere desire for truth that cannot be too much admired ; yet his deductions would be far more convincing if he would substitute a solid for the liquid culture medium. Sattler has recently found rnicrococci, apparently iden- tical with those of gonorrhoea, in the conjunctival granu- lations, and affirms that inoculation with the organisms, isolated by cultivation, induced the disease in a human subject. Micrococci, then, exist in the human body, locally and generally ; yet excepting gonorrhoea there is no decisive evidence that a specific micrococcus is associated ex- clusively with any one specific morbid process in the human subject. But I would again remind you that many of these organisms are individually so minute that absolute, and hence comparative, measurements cannot be as yet accurately made ; further, that micrococci morphologically identical may be physiologically distinct. Hence it can- not be asserted at present that the same species is present in septicaemia, pyaemia, etc., although the contrary is not yet established beyond doubt. Turning to the other tribes of bacteria, however, we find more definite information ; for in size, shape, mode of propagation, often of locomotion also, they present such differences that a distinction into species is often possible. The disease variously designated anthrax, splenic fever, malignant pustule, woolsorters' disease, charbon, and by the Germans Milzbrand, is proven to be not only associated with, but also caused by, a bacillus. About this all controversy has ceased ; inoculation with the bacilli, isolated by filtration, flask cultures, by cultures upon solids, by scores of observers, have always and in- variably given the same result ; Koch has even induced the disease by inoculation with the one hundred and fif- teenth successive culture upon solids. Further experi- mentation is as unnecessary as further proof that a dog can be poisoned with strychnine. Anthrax is as yet 64 the only disease proven to be due to a bacterium, by demonstrations so clear and unequivocal as to convince skepticism and silence sophistry. It is, therefore, the rock of ages on which the bacteriologists seek refuge from the waves of ridicule ; the cross to which they cling amid the storms of adverse criticism ; the strong castle from which they repel the impotent assaults of their enemies. The knowledge of certain facts as to the occurrence of this disease has extreme value for those of us who, having no prejudices nor views to protect, belonging to no camp nor sect in pathology, are actuated by a desire, not to demolish every one whose views do not accord with ours, but to ascertain and interpret intelligently all facts bear- ing upon the relations of bacteria to disease. Anthrax is endemic in some parts of Europe, particu- larly of Russia, Germany, and France, and exists also in the United States. A conception of its extent may be derived from the fact that in one Russian district alone there perished in 1867-70 fifty-six thousand domestic animals horses, cows, and sheep and five hundred and twenty-eight human beings. In 1770 there occurred an epidemic in the West Indies, in which, within six weeks, fifteen thousand men died from eating beef infected with this parasite (Law). Sheep appear to be the natural host of the bacillus, since they are affected during the entire year, while other animals exhibit the disease only sporadically. Anthrax is both contagious and infectious ; is acquired by cattle in grazing in certain localities, par- ticularly after inundations, and in spots where animals similarly infected have grazed ; may be probably acquired through the agency of flies. By man the disease is con- tracted through contact with infected animals, flesh, hides, wool ; by eating infected meat. These clinical facts were established long before the discovery of the bacillus; and have become intelligible and coherent only since the life-history of the parasite has been studied for it is demonstrated that this plant produces spores, which, when placed under favorable conditions, grow into the mature form ; but which, mean- 6; while, may remain in this embryonic state for an in- definite number of years, unaffected by extremes of temperature, by many chemical agents, even absolute al- cohol. The mysterious and inexplicable sporadic ap- pearance of the disease is at once explained. These spores may be transported in the hide, the wool, and the flesh of the animal, either of which may, therefore, cause Fig. 9. Kidney of rabbit ; anthrax bacilli in the inter-tubular capillaries, x 700. (Copied, by special permission, from a photogram by Dr. Koch.) an outbreak of the disease in a distant part of the world, and after the lapse of years. It is reported that anthrax once appeared among the workmen in an upholsterer's shop, limited to those who were engaged in repairing certain chairs, imported from a distance, which were stuffed with horse-hair. Some time ago a whole family ki Scotland acquired the disease after eating soup made 66 from beef by several hours' boiling. A local epidemic occurred in Paris among the workmen who had handled a cargo of hides from South America. The natural habitat of the anthrax bacillus has not yet been discovered, though the plant is evidently indigenous only in certain limited districts. Koch's researches, as well as clinical observations, make it extremely probable that the bacillus is not properly a parasite of animals ; that it, like many other fungi, grows upon living or dead vegetable matter, and its entrance into the cow or sheep is merely incidental to the consumption of its host as food by the animal an accidental excursion from its usual life history just as the presence of the trichina spiralis in the human subject is incidental to the con- sumption of uncooked pork. When we reflect upon the close clinical resemblance between anthrax and certain other infectious diseases ; their occurrence sporadically and epidemically; their usual limitation to certain conditions of climate and of soil ; their especial prevalence during certain seasons of the year; the predisposing influence of heat and moisture ; the stage of incubation ; the contagiousness ; the self- limitation of the disease, etc., it becomes evident to every one whose cerebral functions are normally performed that there may be, in this matter of bacteria, vastly more than the optical delusions of a microscopist, the im- practical fancies of a pathologist ; more than fat-crystals and fibrin threads. Yet it is understood that there may be no conclusions by analogy. Anthrax and septicaemia may be very similar clinically and anatomically, yet the demonstrated parasitic origin of the one does not prove the same for the other ; arguments of that sort have no place in exact science. The matter must be investigated in the case of each disease independently, precisely as it has been in anthrax a fact which is insisted upon by no one more persistently and emphatically than by Koch to whom, by the way, we are indebted for most of what we now know about the life-history of the bacillus an- thracis. And just here is another of those vital differ* 6; ences which distinguish Koch's work from that of Klebs and of Pasteur. The latter seem to assume the parasitic origin of the infectious diseases, and their deductions are but too often partially based upon such assumption. Koch assumes nothing, furnishes ocular demonstration of his assertions and uses all his influence, by precept and example, to raise this subject of bacterial investiga- tion from the mire of uncertainty, doubt, skepticism, and contempt to the firm basis of exact science. For our patience has been so sorely tried, our confidence so often abused, that we have acquired a certain indifference to bacterial discoveries ; we often fail to discriminate ac- cording to the evidence furnished, and regard all alike as essentially uncertain and obscure. In this failure to discriminate between evidence and evidence, between assertions and assertions ; in this fail- ure to distinguish between a deduction and a demonstra- tion, is to be found, in part at least, the explanation of the remarkable attitude, or rather variety of attitudes, maintained by the medical public of our land, and of our land only, on the question to be next discussed tuber- culosis. All pathologists worthy of the name, and I be- lieve all others also, are agreed that the miliary tuber- culosis of man is anatomically identical with the disease caused by the same name in rabbits, guinea-pigs, dogs, and cats ; and that pulmonary consumption results from the aggregation and degeneration of miliary tubercles. From the earliest times there seems to have been a suspicion among medical men that tuberculosis is a com- municable disease ; now and then an instance was ob- served in which a previously healthy individual, of non- consumptive stock, became tuberculous after assuming an intimate relation as of husband or wife to a con- sumptive individual ; and domestic animals, even those not particularly susceptible to the disease, such as dogs, became in some instances consumptive after close attend- ance upon a human subject previously so afflicted. Yet the evidence of such cases, however suggestive, was not decisive ; so difficult is the proof of inoculation, so insid- 68 ions and gradual the inception and manifestation of the disease, so numerous and diverse the other influences to which the individual is exposed, so impracticable the re- striction of personal liberty necessary for accurate ob- servation, that the exclusion of other possible causes for the disease has not been, and probably cannot be, con- clusively demonstrated in the human subject. Clinical observations have therefore never been decisive, either affirmatively or negatively. With experiments upon ani- mals it is evidently otherwise ; and this question was, early in the history of experimental pathology, submitted to experimental investigation. In 1865 Villemin de- monstrated that the subcutaneous introduction of tuber- culous human tissues was followed by local and general tuberculosis in rabbits and guinea-pigs. His results were in succeeding years corroborated by Klebs, Lebert, Waldenburg, Cohnheim, Frank el, Tappeiner, Orth, Bol- linger in short by all who made the experiment ; yet not every inoculation was successful : the animals most frequently subject to spontaneous tuberculosis es- pecially the rabbit and guinea-pig were found also most susceptible to inoculation ; those which rarely exhibit the disease spontaneously the dog and cat, for example often resisted attempts at artificial induction of the disease ; this was to be expected, and was con- sidered, indeed, as clinical confirmation of the ana- tomical evidence as to the identity of the spontaneous and the induced disease. Tuberculosis can, there- fore, according to the unanimous testimony of ob- servers, be induced by inoculation with tuberculous tissue. But it soon became doubtful whether this un- questioned fact could be interpreted as proof that there is anything specific about the tubercle ; for it is evident that if all the effects produced by inoculation with tubercle can be just as certainly induced by non-tuberculous materials, no assumption of specific nature is necessary. It was demonstrated by Burdon-Sanderson, Wilson Fox, Martin, Waldenburg, Cohnheim, Frank el, that after the introduction of mechanical or chemical irritants a piece 6 9 of wood or paper, a linen thread, a cork, glass, pepper, cantharides in short, after the induction of irritation and inflammation in the subcutaneous tissue or peritoneum, an eruption of miliary tubercles, indistinguishable his- tologically from those following inoculation with tubercu- lous matter, often occurred. It is a little strange, by the way, that Dr. H. F. Formad, in a recent paper, called "The Bacillus Tuberculosis," in which he relates the re- petition of these experiments by himself and by one of his own pupils, makes no allusion, direct or indirect, to this work to which I have just referred. This is doubtless an unintentional oversight ; yet in consequence of this over- sight, the casual reader derives the impression that a fact demonstrated by a score of observers in the last fifteen years was discovered two years ago in Philadelphia. And then arose the school, represented among patholo- gists by Buhl and Cohnheim, and among clinicians by Niemeyer, who were inclined to deny altogether the spe- cific nature of tuberculosis, who saw in the etiology of this disease only the caseous degeneration of an inflammatory product, a conception tersely expressed in the phrase no cheesy product, no tuberculosis. Dr. Formad, after re- peating these experiments, has recently arrived at the same conclusion ; but, by a repetition of the singular over- sight already mentioned, he conveys the impression, by his failure to mention Niemeyer, Buhl, and the rest (though citing one of his own pupils) that this doctrine is new. Experimental investigation, however, revealed certain facts that demolished the Cohnheim-Niemeyer theory entirely, as admitted by Cohnheim himself. It had long been observed that wild animals, which in their native state are not known to suffer from tubercu- losis, are prone to the disease when kept in confinement ; and that some tame animals, when closely confined, as is usually the case in physiological laboratories, exhibit an excessive mortality from this disease. Klebs suggested that the successful induction of tuberculosis after the insertion of glass, wood, etc., might after all be simply infection from contact with animals already tuberculous, or from tuber- culous materials left in laboratories by previous subjects of the disease. Cohnheim repeated his experiments on rabbits and guinea-pigs, isolated both from other animals and from the stalls in which animals had been previously confined. The subcutaneous or intraperitoneal intro- duction of mechanical and chemical irritants was under these circumstances followed by tuberculosis in not a single instance. Frankel, who had performed with Cohnheim the original successful experiments in the Berlin Pathological Institute, repeated them in his pri- vate dwelling, with absolutely negative results. Cohn- heim, with the moral courage born of true scientific spirit, published this fact, and acknowledged the justice of Klebs' suggestion. Chauveau, Aufrecht, Bollinger, and others proved that tuberculosis can be induced in rabbits and other animals by simply mixing with their food tuberculous material, and that this tuberculosis begins not in the lungs, nor in some caseous inflammatory product, but directly in the intestinal wall. Giboux placed healthy rabbits in cages in each of two rooms ; into one room was passed, for several hours a day, the breath expired by phthisical patients ; into the other room the same, after filtering through carbolized tow ; in a few months the rabbits in the first room were dead of tuberculosis ; in the second apartment there was no sign of death nor of tuberculosis. Tappeiner, and after him Bertheau, de- monstrated that the inhalation of sputum from phthisical patients in minute quantity is followed by pulmonary, and then general tuberculosis, not only in rabbits, which are so susceptible to the disease, but even in dogs ; and that the inhalation of other sputum did not produce this effect. On the other hand, Schottelius observed among the inflammatory products following the inhalation of irritant particles, such as malodorous cheese, certain nodules histologically identical with spontaneous tuber- cle ; and that similar nodules sometimes followed the prolonged inhalation of non-phthisical sputum in large quantity. (Schottelius, by the way, has since acquiesced in the infectiousness of tuberculosis.) Weichselbaum found a few similar nodules in the lungs of one of three dogs treated in this way, but no tuberculosis. He found further, that the inhalation even when brief, of phthisi- cal sputum induced general tuberculosis ; but after boil- ing, or after treatment with corrosive sublimate, the same sputum produced no tuberculosis, and rarely if ever nodules. These inhalation experiments of Tappeiner, Bertheau, Schottelius, and Weichselbaum illustrate admirably from the experimental side what had been for years acknowl- edged from the histological standpoint : that there is nothing characteristic in the individual nodule. The same histological structure, including the giant-cell, may be found in the nodules of syphilis or lupus, as well as of tuberculosis ; the same local anatomical change may follow the inhalation of large particles of Limburger cheese, as the inspiration of atomized phthisical sputum. For decades the pathologists from Virchow down, their eyes full of caseous matter and giant-cells, wrestled with one another over the question, what is true tubercle? Their hair-splitting disputes remind us of the bitter con- troversies of the mediaeval philosophers as to how many spirits could stand on the po.int of a needle. Finally it dawned upon them they were confounding anatomy with etiology ; they were regarding as characteristic of one morbid process a histological structure common to sev- eral ; they were ascribing to a single cause the common effect of many ; they were confounding tubercle with tu- berculosis. As Cohnheim said years ago : " Struggle against this as we may, there is no help for it the ana- tomical definition suffices no longer for the tubercle and tuberculosis." Even Schottelius, the last of the German pathologists to deny the infectiousness of tuberculosis, has finally recorded his conviction that tuberculosis is certainly infectious, though not all individual tubercles belong to tuberculosis. And what shall be considered a tuberculous tubercle ? 72 Wherein may we distinguish a " true " tubercle from a nodule exhibiting an identical structure ? The question is answered instantly when we consider what constitutes pyaemic pus. Pus is a definite anatomical entity, vary- ing, like tubercle, within certain limits. The pus from a pyaemic joint, may be indistinguishable by the micro- scope from the pus of a simple abscess ; yet there is none the less a vital, or rather a fatal difference. Fresh pus from a simple non-specific abscess does not cause pyaemia, as Virchow long ago proved ; a minute quan- tity of pyaemic pus is fatal through pyaemia, as the death of many a physician has testified. The tubercle from Limburger cheese does not cause tuberculosis, as Schot- telius himself admitted ; the tubercle from tuberculosis never fails to do so, as all observers testify. Pyaemic pus, however similar histologically to that from croton- oil or turpentine, is unerringly distinguished by its infec- tiousness ; tubercles from tuberculosis, though anatomic- ally identical with those from mechanical irritation or from syphilis, contain a something sure to propagate tu- berculosis in the proper soil. The non-specific pus of a simple wound or abscess may acquire pyaemic properties, without the intentional or even conscious introduction of pyaemic matter ; the non-specific cheesy products of a simple inflammation may acquire infectiousness without the intentional introduction of a specific agent. This acquisition of pyaemic infectiousness never occurs, as has long been known, without bacteria ; and the day has come when we can say that the infectious tubercle of tuberculosis is also characterized by a bacterium. Perhaps the clearest proof because a demonstration of the infectiousness of tuberculosis is furnished by com- parative observations upon the eye made by Baum- garten, Cohnheim, Salomonsen, Deutschmann, and others. When the piece used for infection is fresh, Cohnheim says " the irritation at the commencement usually soon subsides, the particle becomes gradually smaller, and can indeed entirely disappear, and for some time the eye then appears entirely clear and intact, until 73 there suddenly appears in the iris a greater or less num- ber of very minute gray tubercles which, precisely like the human tubercles, grow to a certain size, then become caseous, etc. In rabbits Salomonsen and I observed the eruption of the tubercles usually about the twenty- first day after the inoculation, in guinea-pigs a week earlier as a rule." "Yet these observations have first acquired their full significance from the fact that the tuberculosis is generated by the inoculation of tubercu- lous matter only and of nothing else? These are the words of a man who, some years ago, was inclined to the belief, from the fact that the disease may follow sub- cutaneous or intraperitoneal mechanical irritation, that tuberculosis was not an etiologically specific disease. In his " Allgemeine Pathologic," in discussing the same subject, Cohnheim says, " After a few days the cornea is quite clear, the iris thoroughly clean and in perfectly normal condition ; in the aqueous humor there is also no exudate to be seen, so that one can see the piece intro- duced sharply and clearly defined against the lens cap- sule ; and thus it remains unchanged for weeks, except perhaps that the particle becomes somewhat smaller. All at once, in our cases between the twentieth and thir- tieth day, the scene changes ; there arises in the iris tissue a considerable number of small transparent gray- ish tubercles." " Yet the most interesting feature is that in numerous instances, though not always, a more or less extensive tuberculosis of lungs, lymph-glands, spleen, and other organs, occurs. From these experiments it cannot be doubted, first, that the tuberculosis by inocu- lation can develop without the medium of a coagulated exudate, and, second, that it has a stage of incubation." He says further, " Where experiments so positive and so easy of repetition are adduced, it would seem impossible to discuss any longer the question of infectiousness." Until, therefore, we can otherwise explain the fact that general tuberculosis can be induced by mixing small quantities of tuberculous matter (but not by mixing any other tissue) with food ; by simple inhalation of phthisical 4 74 sputum, but by no other sputum, nor even by this after boiling or treatment with corrosive sublimate or nitration through carbolized tow ; that general tuberculosis with- out caseous exudate follows the introduction of a minute tuberculous particle, but of nothing else, into the eye ; until it shall be possible to offer another explanation, we must admit that there is a something peculiar to tubercu- losis and not common to all tubercles. To assert with Niemeyer that the disease originates de novo in a cheesy mass, is to assume that because there is no intentional or conscious introduction of an infectious agent therefore none occurs. Surely no surgeon ever intentionally or consciously introduced pyaemic matter into a wound ; yet infectious pyaemia was formerly the scourge of hos- pitals. Septicaemia, erysipelas, diphtheria, and pyaemia are none the less infectious because there is especially in the so-called spontaneous cases of each no discover- able possibility of contact with previous subjects of the same disease. Infection, in other word-s, does not neces- sarily imply contagion. No man becomes syphilitic un- less there be incorporated into his body material from an individual previously syphilitic ; no man acquires scabies without contact with a sufferer from itch ; but pyaemia, erysipelas, diphtheria, anthrax, and tuberculosis are ac- quired not only by transfer from subjects of the respec- tive diseases, but also without such transfer. The puru- lent secretions of a wound are doubtless favorable soil for the retention and propagation of pyaemic or erysipe- latous virus ; the catarrhal products in the throat for the origin of diphtheritic infection ; the cheesy products of a bronchitis or of mechanical irritation for the location and propagation of the tuberculous infective agent ; but none of these are necessary. Pyaemia, erysipelas, diphtheria, anthrax, tuberculosis occur not only by demonstrable con- tagion, not only after a simple wound without demon- strable contagion, but also without either demonstrable contagion or even a simple wound i.e., spontaneously. Yet in the face of this perfect analogy with other in- fectious diseases, in the face of the experimental proof 75 as above related, there are doubtless many practising physicians who cannot believe that tuberculosis is com- municable. Why ? First, because clinical proof to that effect is unsatisfactory ; a surgeon pricks his finger in dressing a pyaemic patient, and in twenty-four hours has a chill and local symptoms pointing unmistakably to the source of infection ; a physician inspires the breath of a struggling diphtheritic patient, and in three or four days gives evidence that the disease was communicated. Had tuberculosis ever been observed to occur in animals so soon or so violently, were the introduction of tuber- culous as well as of pyaemic and erysipelatous virus ac- companied by chill, fever, and severe acute local inflam- mation (it does seem to be so accompanied in gen- eral acute miliary tuberculosis), there might be reason in the objection that no absolute clinical proof has been furnished. But even when the freshest of tuberculous material is introduced into the most favorable soil, the eye of a susceptible rabbit, two to four weeks elapse be- fore the first local manifestation of infection, and further weeks or months before the evidences of general tuber- culosis are apparent ; there is, indeed, nothing in the animal's history to indicate infection, the proof of which consists merely in the conscious act of inoculation. An observer who was not aware of this act, might honestly believe that the infection which manifests itself weeks or months later is spontaneous even autochthonous ; and some physicians, because they see no transfer of tuber- culous material (though opportunities enough for such transfer are certainly given), because they see no strik- ing symptoms to mark the hour or the day of infection^ insist that no infection has occurred. A man may be shot in the presence of witnesses ; but if we find a body with a bullet in thq heart, we are none the less certain that this body, alive or dead, has been shot, though no revolver nor human agent may be dis- coverable. A man may be killed by the lightning which dazzles all eyes ; but he is none the less killed if the electricity be the invisible current of a powerful battery. . 76 If a man exhibits secondary syphilis, nothing can shake our conviction that he has, whether consciously or not, come into contact, mediate or immediate, with a syphil- itic person, although the sufferer himself may be honestly unable to point out the moment or the mode of possible infection. In many cases of pyaemia and diphtheria the course of the infection is as plain as the track of the lightning ; the effect as pronounced and almost as sud- den as that of the murderer's bullet. In other cases, however, of pyaemia, diphtheria, as well as of anthrax, syphilis, and tuberculosis, there are absolutely no phe- nomena observable in the individual which attract atten- tion to a given moment as the time at which an infec- tion, subsequently manifested, may have occurred. A piece of tuberculous matter introduced into a rabbit's eye may entirely disappear ; and for weeks the animal presents absolutely no signs, local or general, of tuber- culous infection. The opportunities for the usual mode of infection by syphilis are only occasional ; and the attendant circum- stances are such as to impress such occasions upon the mind and conscience ; when, therefore, the first evidence of infection appears, perhaps weeks subsequently, upon that part of the anatomy peculiarly exposed upon such an occasion, it is but natural that the mind should asso- ciate the two phenomena as cause and effect. Were syphilis communicated not in the way at present in vogue, but by inhalation; were the initial evidence of infection not upon the integuments and therefore visible, but in the lungs and hence inaccessible to the eye, there might be the same clinical grounds for doubting the in- fectiousness of syphilis as of tuberculosis. The occurrence of infection in tuberculosis is usually as unobserved clin- ically as in the exceptional cases of syphilis, in which a primary lesion was neither suspected nor discoverable. Another argument often heard against the infectious- ness of tuberculosis, recently uttered and printed by a Philadelphia surgeon, is the fact that we do not all die of this disease. Yet the same argument is valid 77 against the infectiousness of cholera, yellow fever, diph- theria, scarlatina, etc. Indeed, since the death-roll of tuberculosis is greater, year after year, than that of any one or perhaps all of these diseases combined, the argu- ment, if it had any sense at all, would tend to prove the excessive infectiousness of tuberculosis. Such an argu- ment ignores the unquestioned and familiar fact that we are not all equally susceptible to any one of the infec- tious diseases ; even the most malignant cholera or yel- low fever attacks only a portion usually a decided minority of the community. Explain it as we may, there is a something which we may call predisposition, by virtue of which only certain individuals yield to in- fection by cholera or by tuberculosis ; and the fact is, that the number susceptible to tuberculosis seems smaller than to any one of several other infections. Compara- tively few of us attain maturity without having had measles, scarlet fever, and whooping-cough at least ; yet six-sevenths of us complete our pilgrimage without ex- hibiting evidences of tuberculosis. That this is not mere accident is shown by experiment : guinea-pigs and rab- bits rarely, dogs and cats usually fail to respond with general tuberculosis to inoculation with tuberculous ma- terial. Even the deadly anthrax usually fails to destroy carnivorous animals, although the most virulent material be introduced ; and it was long ago pointed out by Chauveau, and often confirmed, that although sheep are very susceptible to this disease, yet some sheep resist all experimental attempts at inoculation, even when large quantities of fresh anthrax material are injected into the animal. Dogs enjoy in general immunity against infec- tion by anthrax ; yet young dogs are often successfully inoculated. Infection implies, therefore, not simply a virus capable of propagation in an animal, but also an animal capable of permitting such propagation. All vari- ations of this relative adaptability may be exhibited be- tween animals of the same species and a given virus. To affirm, then, that a disease anthrax or tuberculosis, for example is infectious is to assert that it can be com- municated by the diseased to a healthy animal, not to all healthy animals, even of the same species. Herein lies evidently our security against tuberculosis, as well as against many other infectious diseases. The general principle the survival of the fittest seems to have been for generations at work in eradicating this disease from the human family, by removing those members of it sus- ceptible to tuberculosis ; the great majority of us now living are as safe from tuberculosis as most dogs are from anthrax. Another, perhaps the most profound, argument against the infectiousness of tuberculosis should be considered here, namely, that the fact must cause us to relapse into barbarism. " Some of the most noble and tender traits of humanity threaten to be undermined. The consumptive who has been heretofore lavishly loved and cared for," etc., " is to be isolated and shunned as a leper, if such doctrines prevail " {Philadelphia Medical News, January 2yth, p. 94). Therefore tuberculosis is not infectious. Incredible as it may appear, the author of these lines is not a clergyman nor a poet, but a distinguished surgeon who does not shun infectious pyaemia, septicaemia, and erysipelas ; and who, we may assume, does not love his child less lavishly, nor care for his patient less faithfully because that child or patient may suffer from infectious diphtheria or scarlatina. Were the susceptibility to tuberculosis as general as to diphtheria, scarlatina, and measles, there might be grounds, not for shunning the consumptive "as a leper," but for the observance of proper precautions for the protection of the healthy many, even at the inconvenience of the diseased few. But since the experience of generations has shown that only about one-seventh of us acquire tuberculosis even with unrestrained intercourse with con- sumptives, it may be questionable whether any other protection than a knowledge of its infectiousness for some individuals be necessary ; we do not invoke the law to brand syphilitic individuals, though to this infection not one-seventh but, probably, all of us are susceptible. But, 79 however that may be settled, let us not confound a fact with a possible deduction which may be unpleasant. These more or less prevalent arguments against the in- fectiousness of tuberculosis have been considered not because they have any bearing upon the question, but because there are those who will not or do not take into consideration the demonstrations attained by accurate ex- perimental methods, and whose opinions rest upon dis- torted deductions from necessarily inaccurate clinical observations. Yet while those who are pleased to regard pathology as something extrinsic to practical medicine are still discussing the clinical proofs of the infectiousness of tuberculosis, it is quite otherwise with pathologists and clinicians whose opinions are founded upon knowledge without prejudice. One after another the German and French pathologists (who are not infrequently clinical teachers as well), honest in their previous conviction that the communicability of tuberculosis was not proven, honestly recorded their convictions as succeeding proofs were furnished, that the case was reversed ; so that three years ago Cohnheim said, "To-day there scarcely exists a pathologist who would deny that tuberculosis is a com- municable disease." 1 Cohnheim himself, extending and repeating more care- fully his observations, saw and acknowledged the error of his former deduction. True, a would-be pathologist has occasionally reminded us that he was not yet con- vinced ; yet even Schottelius, the last of them, has finally yielded the point. There have been in all ages, and on all questions, similar psychological curiosities ; twenty- five years ago it was maintained on the floor of the French Academy of Sciences that intestinal worms origi- nate de novo in a peculiar influence pervading the system the vermicular diathesis. There is a gentleman in this State who recently reminded us that bacteria, so-called, 1 In the Medical News, January 27, 1883, p. 94, Dr. Wm. Hunt leads us to infer that "most recent pathologists " agree in regarding tuberculosis as the result of a simple inflammation. Will he kindly name one pathologist who now holds this opinion, and mention the pertinent publication? 8o are in his opinion fibrin threads and the like ; and there is said to be a man in Virginia who still insists that the earth is flat. You may have noticed that in this discussion the name of Koch has not been mentioned a fact to which I call attention, because a popular impression, not entirely con- fined to the laity, saddles upon Koch the paternity not only of the bacillus, but also of the infectiousness of tuber- culosis. Dr. Formad, for example, says (p. 3) : " An analysis of Koch's experiments shows that he has not proved the parasitic nature of tuberculosis, so that the in- fectiotisness of tubercular disease is still sub judice. " 1 1 i s apparent from the facts which I have endeavored to sum- marize that the communicability of tuberculosis was estab- lished years before the well-known publication of Koch's discovery. Dr. Formad says (p. 10) : " The supreme question before the medical world is now, whether the disease under consideration is really infectious." This statement may represent faithfully that portion of the world bounded by the city limits of Philadelphia ; the supreme question before that portion of the medical world including Virchow, Cohnheim, Billroth, Bamberger, Weigert, Villemin, and the other German, French, and Austrian pathologists and clinical teachers is, not whether tuberculosis is infectious, but whether the bacil- lus of Koch is the infective agent. For them the two questions are quite independent the former established, the latter awaiting confirmation. The numerous examinations of tuberculous tissues re- vealed occasionally bacteria, which the discoverers were but too willing to consider the cause of the disease ; Klebs, Schiiller, and Aufrecht severally announced but failed to demonstrate that the infective agent had been found and that it was a bacterium. The lack of evidence in support of their statements, as well as the reserve with which such assertions in general were received, combined to reduce to a minimum the attention bestowed upon them. Such was the state of affairs when Koch read before the Physiological Society of Berlin a paper 8i whose contents were in forty-eight hours telegraphed over the world. Koch's statements are so familiar to all, that detailed repetition would be superfluous ; they may be summarized in the assertion that the active agent in the induction and propagation of tuberculosis is a distinct species of bacterium, a bacillus ; that tuberculosis does not occur without the presence of this organism ; that conversely all those anatomical changes and only those should be called tuberculosis whose point of departure from the normal condition is the presence and vital ac- tivity of this bacillus ; hence, general and local miliary tuberculosis, cheesy pneumonia and bronchitis certainly, fungus-joint granulations, scrofulous inflammation of lymph-glands probably, and the pearl disease of cattle, are etiologically identical. The point of chief interest is of course the assertion that tuberculosis and cheesy pneumo- nia, pulmonary consumption, are caused by the bacillus. The evidence in its favor is first the experimental work of Koch himself, and then the unanimous confirmation of those of his statements which have been already tested. His experience with and knowledge of bacteria found in the animal body is by general consent admitted to be excelled by that of no other observer ; his caution and conservatism and the accuracy of his methods are such that, although he has for eight years been constantly working and frequently writing on this subject, he has never as yet been detected in a single error of observa- tion ; his facilities and opportunities in the Imperial Ger- man Health Bureau are unexcelled. The confidence and good will of government and people alike for Koch's is an official position, you know would be de- stroyed by any ill-executed observations, or by any in- judicious and untenable assertions in this, the most im- portant and widely circulated of all his works. That Koch appreciated the situation is shown by his course in the matter : having discovered the bacilli in tuberculous tissue, he did not send an announcement to the Academy of Sciences nor blazon it through the medical press ; he 4* 82 kept it to himself, satisfied himself that this was a con- stant, not an occasional or accidental association ; that the same bacteria were present in the spontaneous tuber- culosis of animals the hog, chicken, ape, guinea-pig, and rabbit ; then he devised, by experimentation, a proper medium, solid of course, for cultivating the organisms outside of the animal body under constant microscopic supervision, comparing them with fresh bacilli from tu- berculous tissues ; satisfied himself again by personal experiment of the inpculability of tuberculosis ; found that while vaccination of the rabbit or guinea-pig with fresh tuberculous matter induced the disease, inocula- tion with such material after lying in alcohol for a month or dry for two months, was impotent to cause the disease, and contained no living bacilli ; found that the bacteria were often, not always, present in the sputum of tuberculous patients, but never, so far as examined, in that of others. Having thus made a preliminary investi- gation, Koch proceeded to the experimentum crucis with bacilli which had grown from the tuberculous tissue under his eyes ; which were therefore proved to be the progeny of the original ones, not by the theory of probabilities, not simply by their identical size, shape, and chemical reaction, but by the fact that he had seen them proceed from the first as continuities of structure ; which were seen under the microscope to be quite free from any foreign solid matter, bacterial or other; which were proven to be equally free from any foreign matter in solution because growing in successive cultures upon solid soil ; which had been carried from the first to the eighth generation ; which had been thus isolated from the original animal tissues three, four, five, even six months. With these isolated descendants of the bacilli found in tuberculous tissues, Koch inoculated numerous animals using over two hundred altogether not only the susceptible rabbits and guinea-pigs, but also cats, a dog, white rats which had resisted inoculation by injec- tion and by feeding with tuberculous materials, and field mice. Inoculation was made in the skin, the abdomen, 83 the eye. In every case tuberculosis and tubercle bacilli were found in the infected animal. Having spent two years in the completion of this work, amid all the facilities of the imperial laboratory ; having meanwhile permitted himself no public intimation of the same, Koch quietly announced his results at a regular meeting of a medical society, with as little ostentation as if he had merely appropriated a chapter from Ziemssen. One whose knowledge of bacteria and of disease is not such as to permit a technical appreciation of Koch's work, cannot help seeing in the unobtrusive, systematic, and undeviating work of two years, and in the modest announcement of the result, that Koch's work is not to be classed with that of Klebs. or Letzerich, or even Pas- teur. I would call your attention to the fact that Koch's assertion embodies not a theory, but simply an ocular demonstration. If a man is seen to plunge a knife into the heart of another the killing is a fact, not a theory ; if Koch saw tuberculosis invariably follow the introduc- tion of isolated bacilli, the relation of cause and effect is a fact, not a theory. There is only one possible escape (I use this word intentionally out of regard for the prejudices of many friends) from the conclusion that the bacillus causes tuberculosis ; and this forlorn hope is the possi- bility that Koch did not see what he says he saw that he made some vital error of observation. This is of course possible, though if true it will be the first error that the most searching scrutiny could ever detect in his observations ; that it is improbable is evident. If we accept Koch's observations as accurate, there is only one conclusion that these bacilli cause tubercu- losis. For here the conclusion and the observation are identical ; this is not a deduction, but a demonstration. And how shall it be decided that this work is or is not free from errors of observation ? Certainly not by say- ing that it cannot be so ; not by exhuming Niemeyer's buried argument that tuberculosis is not infectious ; but simply and solely through the repetition, by competent observers, of the same work. Until such repetition shall 8 4 detect serious errors of observation, Koch's work stands unchallenged more accurate and complete investigation can scarcely be conceived. On the other hand, until such repetition shall confirm Koch's observations, we may justly decline to accept them unreservedly, on the ground that he may have made his first error in this his greatest effort. While, however, Koch's main assertion, that the bacilli cause tuberculosis, can be competently criticised only by the few men who like himself have the time, facilities, and skill necessary to conduct such tedious and delicate experimental observations, yet some of the preliminary assertions fall within the range of a larger circle of critics, and have been already subjected to extensive investiga- tion. The results are as yet unanimous in confirming the original assertions of Koch that the bacilli are to be found in the sputum from most though not all cases of pulmonary tuberculosis, and, what is quite as significant, have never been found in any other sputum. Ehrlich, Balmer and Frantzel, Guttrnann, d'Espine, Lichtheim, Frankel, Ziehl, Heron, Gibbes, Green, West, Yeo, Whipham, Councilman, have already recorded their unanimous experience that while the bacilli are found in the sputum in at least a large majority of cases of pulmo- nary consumption and tuberculosis, they are not found in any other disease. Balmer and Frantzel found them always in their one hundred and twenty cases, but never in 'bronchitis. Ziehl recognized them in nearly all of seventy-three cases, but never in thirty-four other cases, including acute and chronic bronchitis, acute fibrous pneumonia, gangrene of the lungs indeed all pulmonary diseases that he had opportunity to examine. It should be remembered that Koch failed to find them in the -spu- tum from a certain number of cases. In the tubercles of tuberculosis and in the cheesy matter of consumptive lungs the bacilli are usually present not always, as Koch himself discovered. Whether their absence from certain tubercles is to be explained, as Koch suggests, by the death of the organisms and their consequent fail- 85 ure to absorb aniline colors, or whether some of these tubercles arise from other causes than the presence of these, may be perhaps an open question. Gibbes' ex- perience that the bacilli are present in only one reticu- lar nodule out of ten, but in nearly all non-reticular tubercles might, perhaps, support another explanation. Certainly the absence of the organisms from tuberculous tissue is the exception. On the other hand, the bacillus is never found in the body except in tuberculosis ; the only suggestion to the contrary is the recent assertion of Koranyi that he found similar organisms in a case which he believed to be pulmonary syphilis, and not consump- tion. Such, then, is the state of the case to-day : Koch's assertion of the association of the bacillus with tubercu- losis its presence in every case of the disease, its ab- sence in all other morbid conditions confirmed by all who have investigated ; his assertion of the causal relation of the parasite to the process based upon a demonstra- tion unexcelled in the history of experimental science for accuracy, clearness, and completeness as yet unchal- lenged. The subject might be properly left here ; but I deem it advisable to consider briefly two recent publications, not because they demand consideration by one familiar with the facts, but because they may have influenced some who derive their information chiefly from American liter- ature. A few months ago there was heard a scream of exul- tation from a Western journal, soon echoed on many sides. The attention of press and -public alike was at- tracted to the jubilant cry that Koch, bacillus, and bac- teria were to be annihilated ; that the " bacillary craze " of German pathologists ; the absurd fancy that a small organism could harm a large one ; the comical idea that an experienced mycologist should know more about bac- teria than a practising physician ; the barbarous doctrine that our loved ones could be subject to infectious dis- eases ; all these and similar absurdities which pseudo- 86 scientists had vainly attempted to foist upon our superior intelligence would be forever buried. The American eagle, that implacable devourer of microscopic poultry, would consent to leave for a brief time its favorite swamp at the "delta of the Mississippi," and by a single act of deglutition would teach our terrified friends, " the micro- pathologists," to " take their eyes from their mounted specimens," and engage in less disreputable pursuits. So ran the widely advertised programme. After weeks of joyous anticipation the appointed day arrived; a distin- guished microscopist, whose skill in mycology had been amply indicated by his failure to detect the bacilli always present in leprous tissue, appeared in the arena armed with the startling discovery that if caustic potash solution be added to fattily degenerated tissue, crystals of fatty acid appear ! The announcement was greeted by the audience of assembled experts with rounds of applause " Sic transit bacteria," etc. Again has free America re- pelled the assaults of effete Europe. I had intended to offer some remarks upon this matter, suggested by the evident fact that Koch's bacillus and Schmidt's crystal were different objects; but criticism is no longer necessary. Dr. Whittaker has stated the case very clearly ; Dr. Hunt has shown that the crystal polar- izes light, while the bacillus does not ; and I have re- ceived from Dr. Schmidt a letter which disarms criticism. After reading his article, I sent him a slide of sputum containing the bacilli ; in his reply he says, "From what I understand now the minute crystalline rods which I dis- covered are not identical with Koch's bacilli ; " and later, "the failure with which I met in my attempts of staining the bacillus tuberculosis, appears to have been due to the worthless aniline oil which I have used." I interpret these sentences as a candid admission that the crystal and the bacillus are not identical, and shall there- fore refrain from further remark. Such admission, by proving sincerity of purpose, transfers to his friends of the antibacterial "camp" the obloquy and chagrin con- sequent upon the blare of trumpets with which this pub- 87 lication was heralded ; the mouse may be per se a highly respectable and by no means ridiculous animal, though its advent as the result of herculean efforts at parturition is said to be very absurd. This entire matter can hardly fail to teach far more effectually than lectures, that trust- worthy investigations on this subject demand not only skill and experience in pathology, which Dr. Schmidt undoubtedly possesses, but also acquaintance with the special methods involved. A paper called " The Bacillus Tuberculosis," by Dr. H. F. Formad, of Philadelphia (Philadelphia Medical Times, November 18, 1882, reprint), opens with the an- nouncement that the author " will bring forward some points from researches of my own, which will check the acceptance of the doctrine of the parasitic origin of tuber- culosis ;" " my anatomical researches will also surely throw grave doubts upon the correctness of Koch's views on the etiology of tuberculosis " (p. 2). The author fails to discriminate between the bacillus and the infectious- ness of tuberculosis, which is in this article, however, a matter of little consequence, except as an index to the general accuracy of the publication. The original researches which are to destroy the "parasitic theory" consist, curiously enough, in the time- honored demonstration that tuberculosis often occurs in certain animals (notably the rabbit and guinea-pig) after simple wounds, the irritation caused by glass, etc. ; especially if the animals be carefully confined in a patho- logical laboratory where many others have died of this disease. As Dr. Formad has seen " more than one hun- dred rabbits, out of five or six hundred operated upon," die of tuberculosis, we may infer that in his laboratory there was no lack of tuberculous material for infection. There is, however, one original feature in this work as reported by Dr. Formad. Actuated doubtless by a com- mendable high- tariff spirit of protection for American industry, while quoting copiously his own students, he resolutely ignores the work of Burdon-Sanderson, Cohn- heim, and a dozen others who have, during the last 88 fifteen years, performed the original experiments of which his own are repetitions ; and neglects to state that Cohnheim and Frankel found that while these experi- ments succeeded admirably in the Berlin laboratory where many animals had long been confined, no tuberculosis occurred in a subsequent repetition in a private dwell- ing. On the same principle, perhaps, he neglects to state that for such reasons as these, such experiments as his own were years ago abandoned to amateurs, while the battle for infectiousness was fought and won in the eye, the lung, and the intestine, as above stated. Perhaps Dr. Formad will kindly explain how he came to deny the in- fectiousness of tuberculosis merely on the strength of these long since abandoned experiments, without a sol- itary experiment, or even reference to an experiment, on the eye, etc. Because in his experiments no tubercular matter was "intentionally or knowingly" introduced, he maintains that nothing could have entered ; that the disease is there- fore not specific nor infectious. Surgeons, then, intention- ally and consciously inoculate their patients with pyaemic, diphtheritic, and erysipelatous material. It will not help Dr. Formad to deny, as a New York microscopist in the same dilemma has curiously done (MEDICAL RECORD, March 3, p. 247), that pyaemia is infectious. For in the National Board of Health Bulletin, Sup. No. 17, Formad asserts and attempts to prove the infectiousness of diph- theria, and says (p. 18) : "A case may begin as one of sthenic pseudo-membranous croup, and end as one of adynamic diphtheria with blood-poisoning ; and in cases of this character, not infrequently, no exposure to conta- gion is discoverable" 1 Perhaps he will explain why the absence of intentional or conscious inoculation, even of discoverable exposure to contagion, is perfectly com- patible with the infectiousness of diphtheria, and yet proves the non-infectiousness of tuberculosis. Formad says (p. 2) : "I can positively prove that true tubercu- 1 Italics mine. 8 9 losis may be produced without the bacillus in question." The only proof adduced for this important statement is the experiment with glass, etc., in which the disease oc- curs without any " conscious or intentional " introduction of the bacillus, and the assumption that the organisms were therefore absent ; if, however, the parasites be never- theless present in such cases, this assertion is evidently unwarranted. We are not informed on this point in the paper, although we may infer their presence from the fol- lowing statement (p. n): "Koch has discovered that tubercle-tissue is always infested by bacilli, and this is correct." To secure definite information, I addressed to Dr. Formad some months ago, three several letters enclosing stamps, requesting him to state for incorporation in these lectures, whether he had examined these cases of tuberculosis following wounds, mechanical irritation, etc., to ascertain the presence or absence of the bacilli, and if so, with what result. To these letters I have received no reply. As to the association of the bacilli with tuberculosis, Formad's limited observations seem to agree with Koch's statements. 2 The one novelty which I am charitably disposed to think explains the existence as well as the peculiar char- acter of this paper is a theory that the susceptibility to tuberculosis is inversely proportional to the width of lymph- spaces ; whence (by a process of reasoning peculiar to the author) he makes the deduction that no etiological influence other than inflammation and narrow lymph- spaces is necessary to induce tuberculosis. It is useless to remind Dr. Formad of the induction of tuberculosis in the eye, lung, and intestine, since he ignores pathological work which does not emanate from himself or his pupils. But since by a singular coincidence the rabbit and guinea- pig the animals exhibiting typical narrow lymph-spaces 1 Koch, by the way, does not make this statement, which is, moreover, not cor- rect, since Koch, Gibbes, Ziehl, Guttmann and others failed to detect the bacilli in a certain number of tubercles. a Paradox: "Tubercle tissue is always infested by bacilli," yet "true tuber- culosis may be produced without" them. 90 i are peculiarly susceptible, the dog and eat insusceptible to anthrax as well as to tuberculosis, I would suggest the possibility that the etiology of anthrax also may be found, not in a bacillus as the Europeans suppose, but in nar- row lymph-spaces. 1 Dr. P'ormad promulgates the dogma (p. 3) " Scrofulous beings " (i.e., those with narrow lymph-spaces) " can have no other than a tuberculous inflammation, although it may remain local and harmless." Are scrofulous beings, then, assured against syphilitic, erysipelatous, diphtheritic inflammations, or are these merely varieties of the tuber- culous ? As yet the presence of the bacillus in sputum has pos- sessed a confirmative rather than a diagnostic value, for in the cases in which it has been detected the diagnosis has been usually already assured by the physical signs. Whether or not the bacillus may be present in cases called chronic bronchitis, etc., where the symptoms and the family history beget a suspicion not yet supported by physical exploration, must be decided in the future. In this connection it may be proper to mention an in- stance which has fallen under my own observation. 2 A young gentleman of my acquaintance, in whose family history there is no record of consumption, but who had for months suffered from a persistent and annoying cough, requested me one day to examine a microscopic slide which he had prepared. The diagnosis was easy, tubercle bacilli in sputum. He then informed me that the sputum was his own. Physical exploration by one of our most experienced physicians revealed subse- quently a circumscribed area of consolidation in the right lung. Frankel has always found the bacilli in laryngeal ulcers of tuberculous patients, but never in those of syphilitic 1 Dr. Formad will enlighten us, in subsequent " Pathological Studies," as to what he will permit us to call " true" tubercle, and announces that a student of his is incubating a cognate topic- Possibly we may yet learn what constitutes " true" pus ; and how many spirits can stand on a needle-point, a I have recently learned from my friend Professor W. H. Welch, of NewYork, that two essentially similar cases are known to him. or other individuals. Barrow found them in the urine from tuberculous kidneys in one case. Not only the clinical, but also the anatomical investi- gation already reported, confirm Koch's statement that tuberculous tissue, whether occurring in miliary nodules or as cheesy masses, whether in lung, or liver, or spleen, peritoneum, or meninges, contain tubercle bacilli, and that no other tissue harbors them. Some, it is true, find a larger proportion than did Koch, of individual rniliary tubercles in which no bacilli can be detected ; this is particularly true of Ziehl's examinations. Gibbes found the bacilli in reticular tubercle in only one nodule out of ten, in the non-reticular they were usually present. Koch was inclined to the belief that his failure to detect them was due to the fact that the organisms had lost their vi- tality, and hence their power of absorbing aniline dyes ; and demonstrated instances in which a very imperfect staining of individual bacilli was visible. This explana- tion is certainly plausible, yet it is possible that tubercu- losis, like individual tubercles, may be produced by any one of several causes. The clinical picture exhibits many variations ; the histological structure is not peculiar to tubercle. We have learned to distinguish trichinosis from typhoid fever ; charbon symptomatique from char- bon ; actinomycosis from pyaemia and pulmonary con- sumption ; indeed, Pflug observed in the lungs of a cow a miliary tuberculosis, and upon microscopic examination was surprised to find that the individual tubercles con- tained, not Koch's bacillus but the actinomyces bovis ; this as yet solitary observation strengthens the suspicion that among the numerous agents whose presence excites the inflammation which results in tubercle formation, there may be other parasites than the bacillus of Koch ; that there may be several diseases etiologically distinct, but anatomically so similar as to be included under the common name tuberculosis ; the one characterized by the famous bacillus, others, possibly, by organisms yet to be discovered. In one instance, certainly, an analogy to this supposition has become a demonstrated fact. For 9 2 thirty years it has been known that the disease called anthrax or charbon is characterized by the presence of a large bacillus ; yet in some cases the site of inoculation was indicated not by a malignant pustule or carbuncle, but by a local necrosis with subcutaneous formation of gas. These cases were designated charbon symptoma- tique. Five years ago Bollinger discovered that the ba- cillus found in the so-called charbon symptomatique is another variety than the bacillus anthracis which charac- terizes the malignant pustule distinguished by both morphological and physiological features. And now the two diseases are recognized as etiologically distinct, though anatomically and clinically almost identical. To-day we can say with Schottelius, that one infectious disease, one infectious tuberculosis, is characterized by the presence of Koch's bacillus, though there may be others, clinically and anatomically entitled to the same name, which future research may distinguish etiologi- cally from this tuberculosis, just as charbon sympto- matique has been distinguished from charbon. Indeed, some observers have already expressed the suspicion, based on their own investigations, that there is more than one bacillus tuberculosis. The association of Koch's bacillus with tuberculous tissues, and its absence from other structures, is there- fore demonstrated and acknowledged ; and this fact, taken in connection with Koch's own demonstrations, constitutes an array of evidence which has induced nu- merous German, Austrian, and English pathologists to accept as a fact the vital activity of the bacillus as the starting-point of the disease. Among these is Billroth, whose acquiescence is notable not merely because of his eminence as pathologist and surgeon, but because his own elaborate researches upon bacteria, published in 1874 an d still widely quoted, led him to the conclusion that these organisms appeared in human tissues as the result, and not as the cause of morbid processes. Billroth, like the German pathologists generally, is open to conviction. Yet while we may have, probably have, found in this 93 bacillus the object whose presence is followed by tuber- culosis, we may not forget that the appearance of the disease implies not only the presence of this organism, but also the existence of animal tissues which permit the bacillus to exercise its vital functions. Many ani- mals, even some rabbits, resist inoculation with the freshest tuberculous material. There 'is, in other words, a predisposition of the animal an adaptation of his tis- sues favorable to the growth of this organism. The palm- tree cannot grow in Greenland ; the oak does not flour- ish in the desert ; the bacillus anthracis and the bacillus tuberculosis rarely grow in the body of a dog. And it may not be forgotten in the excitement over Koch's discovery, that there remains much to be done in deter- mining the nature of this predisposition of the animal soil to the growth of the tuberculous plant. Thus far we are utterly in the dark. Dr. Formad thinks he discovers a ray of light issuing from certain narrow lymph-spaces. If he will prove what he asserts, he will have made a valuable anatomical contribution ; yet when we remem- ber that rabbits and guinea-pigs are peculiarly susceptible not only to tuberculosis but also to anthrax, and that cats and dogs are as markedly insusceptible to the one disease as to the other, it becomes evident that there must be some factor in the common predisposition to both diseases alike, which is not visible in the field of the microscope. Indeed, with all due honor to Koch, and admiration for the most brilliant of experimental researches, we must ad- mit that the discovery of the bacillus has chiefly an ana- tomical value : it localizes in this organism the infectious principle which had long been known to exist; it enables us to distinguish ante- and post-mortem infectious tuber- culosis from inflammation, tubercular or other, due to other causes ; but it does not as yet explain the hereditary predisposition, nor why this infection occurs in one man and not in another exposed to the same influences. A dozen questions should be considered in this con- nection the etiological identity of scrofula, tuberculosis, and fungus joint granulations ; the possible infection of 94 the infant by the mother's breath and breast, by the ap- plication of a handkerchief to the child's nostrils, etc. Yet time permits a reference, and that but brief, to one of the most important the possibility of infection from tuberculous meat and milk. For the so-called pearl disease of cattle, while presenting certain histological differences an excess of calcareous salts, ascribable to their vegetable food from tuberculosis in man and other animals, would seem to have an identical etiology ; since inoculation with minute pieces into the anterior chamber of the rabbit's eye gives precisely the same result local and general tuberculosis as is induced by the same quantity of human tuberculous tissue and by nothing else. The effects of introducing the two into the circulation are also identical. Indeed there now remain but few who are not satisfied of the etiological identity of the two pro- cesses, especially since Koch's bacillus is found to in- habit both tissues. Yet etiological identity does not prove the possibility of infecting the human subject with tuberculous meat and milk. For it is a principle that must be borne in mind a principle which Pas- teur, in his ideas of preventive vaccination seems to have forgotten, by the way that a material which can infect a given animal when placed in the eye, may fail when introduced into the alimentary canal or even under the skin. Koch found, five years ago, that al- though a mouse is so susceptible to anthrax as to be a reliable reagent in testing the strength of anthrax material when introduced subcutaneously, yet all attempts to in- duce the disease in mice, as well as in rabbits, by feeding them with anthrax tissues or spores, were quite unsuc- cessful. Since anthrax bacilli grow best in a somewhat al- kaline liquid, and not at all in one markedly acid, the explanation may lie in the general acidity of the gastric and intestinal secretions in certain animals. But what- ever the explanation the fact remains. Many experiments have been made to determine the possibility of infecting animals by feeding them with tis- sues and milk from tuberculous cattle. Gerlach, Orth, 95 Bellinger, Klebs, and Chauveau were almost invariably successful with herbivorous animals ; but Colin, Giin- ther, and Miiller saw only negative results. Virchow, experimenting with pigs, achieved somewhat indecisive effects ; and while not inclined to deny the identity of the two diseases, he thinks it not yet experimentally proven that tuberculosis can be induced in animals by feeding them with such meat and milk. While we may quite agree in this, yet when we consider ike probability on anatomical and experimental evidence j when we re- member the peculiar frequency of intestinal tuberculosis in infants, especially in those artificially nourished ; when we think that thirty per cent, of certain herds of cattle are, according to Professor Law, demonstrably tubercu- lous ; we may be inclined to dispense with further direct experimental evidence, and avoid such meat and milk. LECTURE IV. IN this discussion I have referred to various bacteria as distinguished into species by essential differences of form and function. In these latter days it has become fash- ionable to speak of these minute organisms as transient modifications, due to incidents of their environment, of one and the same organism. Nageli, indeed, would in- clude not only bacteria, but also some of the higher fungi in this hypothesis. As this seems as yet a specu- lation, based not so much upon direct demonstration, as upon deductions, it will not require discussion here. An essential element of this theory, however, the so- called accommodative cultivation of bacteria, seems to be supported by certain experimental evidence. This assumes that the physiological characteristics may be modified by contact with unusual influences by a change of environment, in other words as to render the de- scendants of a given bacterium which is capable of successful contest with the living animal tissues impo- tent to maintain such combat ; and conversely to confer upon a previously harmless bacterial species the power to invade and destroy a living animal. This hypothesis is so fascinating, the solution of many difficult problems is rendered thereby so simple, the reconciliation of con- flicting observations and opinions becomes so easy, that every man becomes at once his own bacteriologist. Diphtheria, on this hypothesis, is not due to a specific bacterium, but to some of those usually guileless organ- isms which ordinarily inhabit the healthy throat, incapa- ble of harm ; but which, excited into unusual and per- verse activity by unknown influences of atmosphere, etc., invade the body with disastrous results. The application of this assumed principle is evidently limited only by the fancy and ingenuity of the individual ; we have been al- ready amply entertained by theories ascribing typhoid 9? fever to the hypothetical tonic influence of sewer-gas upon the bacteria inhabiting the alimentary canal, etc. The evidence in support of this hypothesis consists of deductions by analogy and of experimental observations. Since the life of an organism is the resultant of many forces, it is a priori evident that a modification of one or more of these forces may be followed by a change of the resultant life. In the higher plants and animals we have abundant evidence to this effect ; the domestic pigeon and the dahlia are examples rendered familiar to us by Darwin. Such modifications, it is true, require time ; but in biology time is measured by generations, not by years ; and since from one bacterium a second may be produced in thirty to sixty minutes, it is evident that a day may induce in these organisms the effects of a thou- sand years in man. The evidence by analogy with higher organisms supports then the theory in question. This same principle modification of function by changes of environment which Grawitz and Buchner had vainly attempted to demonstrate, seems to have been demonstrated by Pasteur in his studies upon pro- tective vaccination. He asserts that the microbes which he regards as the morbid agents in chicken-cholera can be deprived of their virulence by successive cultures in contact with air ; so that a given quantity of such culture fluid causes effects far less severe than the same quantity before such modification. Pasteur subsequently applied the same principle to the mitigation of anthrax virus ; indeed the list has been still further extended by himself and others. Since in all these cases the same general principle is illustrated, it will suffice for our present pur- pose to consider the mitigation of anthrax virus for the preventive vaccination of sheep. Pasteur's theory is this : the anthrax rods, as found in the blood of an animal dead of the disease, when placed in a suitable liquid maintained at a temperature of 42-43 C. grow as usual into threads, but do not produce spores. After a certain time their vitality is lost ; when transferred to another flask, kept tinder the same conditions, they do 5 98 not grow nor reproduce. But at any time previous to this final extinction of vitality, the bacilli still exhibit life, though their ability to invade a living animal, i.e., their malignancy, is diminished. There occurs, indeed, a grad- ual diminuendo of malignancy, their morbid effect upon an animal decreasing with the prolongation of their ex- posure to these conditions, high temperature and exclu- sion of oxygen, until finally both life and malignancy are extinguished. Pasteur found that after eight days the bacilli had lost their fatal power to destroy rabbits, guinea- pigs, and sheep, though these animals are peculiarly sus- ceptible to this virus. He claims that he has thus miti- gated the virulence of these bacteria, has induced a modification of function. As to the accuracy of Pasteur's observation in this case there can be no doubt ; the vaccination of thousands of animals has already proven that the mortality induced by such anthrax cultures is much less than that following the usual inoculations with fresh virus. But his explanation, that the decrease of malignancy is due to modification of physiological function, is a by no means necessary con- clusion, since precisely the same results can be and have been secured, under circumstances which preclude the possibility of a transmissible physiological modification. First among these methods is simple dilution. It has been long since and often demonstrated that the effect induced by the incorporation of these virulent organisms into an animal depends, catcris paribus, upon the number introduced. Chauveau found that sheep which had sur- vived injections of fifty to six hundred anthrax bacilli died after subsequent injections of one thousand bacilli each. Oemler had previously made analogous observa- tions upon horses ; Loffler upon rats ; it is indeed an ac- cepted principle that the effect of inoculation increases with the number of injected bacilli. The somewhat general impression that quantity exerts no influence upon the result, except as to time, maybe true when the effect is manifested upon an inert, unorganized mass, but not in the case of a living animal. 99 Diminution of malignancy can be secured in other ways also, which seem to accomplish practically the same result, dilution of the virus. Nocard and Mollereau found that anthrax virus is attenuated by simply mixing it with twice its volume of oxygenated water under pressure. Four hours' contact produces Pasteur's premier vaccin (for the guinea-pig), ninety minutes' exposure the second. Chauveau makes the premier vaccin by exposing anthrax blood to a temperature of 50 C. for fifteen minutes ; and the second vaccin by the same exposure for nine to ten minutes. Since oxygen under pressure, as well as a high temperature, destroys the anthrax bacilli, it would seem that these methods accomplished merely a dilution of the virus by killing a certain number of the contained organ- isms ; for in the brief time required in these experiments a physiological modification seems scarcely possible. According to a communication presented by Bouley to the French Academy of Medicine, Peuch discovered that the effects of tag-sore virus (variola in sheep) de- creased by simple dilution with distilled water. Is. In the case of chicken cholera also, the characteristic organisms of which have been " modified " by Pasteur through a long and interesting process, there is reason to suppose that this modification may be simply a dilution. For vaccination against the disease has been successfully practised by simply introducing into the animal a piece of blotting-paper on which the blood of an infected ani- mal has dried. The bacteria in dried anthrax blood die in a few weeks, but those still living at a given moment exhibit their original functions if transferred to a proper soil, and it seems probable that the diminished virulence of dried chicken cholera blood is due to the death of some of the contained organisms rather than to a physio- logical modification. This belief is strengthened by a letter recently received from Dr. D. E. Salmon, of Ash- ville, N. C., in which he says : "I have vaccinated fowls experimentally, both by Pasteur's method and by a method of my own. My method is simply inoculation with a very diluted virus ; when sufficiently diluted it IOO produces only a very circumscribed, local irritation that does not affect the general health in the least. One or a dozen germs of this fatal disease may be introduced in the tissues and are unable to produce any effect what- ever. Twenty, fifty, or a hundred, according to the sus- ceptibility of the fowl, will produce a slight local irrita- tion. Pasteur's method requires five to nine months to attenuate the virus ; by mine it is accomplished in as many minutes." The effect can be secured, therefore, by simple dilution of anthrax or chicken cholera virus, as well as by Pas- teur's cultures, and there are other reasons for suspect- ing that his mysterious method for the mitigation of bac- terial virulence is practically a dilution of the culture, or rather, of the contained bacteria. If Pasteur would demonstrate that his tamed bacilli transmit their tame- ness to subsequent generations, the question would be finally settled ; he asserts, indeed, that he has observed such transmission "in a few cultures." but gives no par- ticulars, while the extensive vaccinations already per- formed on sheep prove that even his first (weak) vaccin sometimes kills an animal. It is but just to state that Koch has recently expressed his conviction that a gen- uine physiological modification does occur in Pasteur's cultures ; whether this conviction is based upon personal observation or not does not appear. 1 Although proper functional activity may doubtless de- crease susceptibility to infectious diseases, whether of bacterial or of still unelucidated origin, it is evident in our daily observation that such activity does not neces- sarily confer immunity. At present but two avenues to such acquisition are known, a natural attack, and the artificial induction of the disease in mitigated form. The immunity secured by one attack of variola, scarlatina, measles, whooping-cough, etc., and by artificial inocula- tion with variola, as was formerly extensively practised, 1 1 have not succeeded in procuring Koch's monograph ; the above statement is taken from reviews of it in French and German journals, the Deutsche Med. Wochenschrift, and the Revue Scietitifique, especially. IOI prompted experimentation in regard to other diseases. In- oculation of cattle with material from animals dead of in- fectious pleuro-pneumonia lung plague was begun in Holland in 1852, and soon extended to Germany and Rus- sia. In Saxony the mortality, previously twenty-five to thirty per cent, of the herds, became ten, six, two, even one per cent. At the Cape of Good Hope, where seventy to eighty per cent, of the cattle died of this infection, the disease almost vanished after inoculation was extensively practised. The tag- sore of sheep was always robbed of many victims by artificial inoculation. But of the diseases of whose parasitic origin we have conclusive or strong pre- sumptive evidence, every one may occur more than once in the same subject. It is evident therefore, first, that im- munity against an infectious disease, in the ordinary sense of the term, implies not necessarily the absence, but merely a relatively slight degree of susceptibility ; second, that the question must be studied as to each dis- ease independently of all others. Although the question of protective vaccination has been experimentally studied as to anthrax, charbon symp- tomatique, chicken cholera, septicaemia, by Chauveau, Toussaint, Semmer, Colin, and Rosenberger, yet the re- sults are so closely associated with Pasteur's name and with anthrax that I shall omit extended reference to the pioneer workers and works, and consider as the most favorable example, the well-known experimentation in protecting sheep against anthrax by inoculation with the cultivated bacilli. This method of Pasteur, I might say, is the first one which has afforded results at all satis- factory ; and the principle differs from that employed in lung-plague, tag-sore, etc., in that the artificially cultivated organisms isolated from the accompanying animal tis- sues are employed a new departure therefore. In considering this subject, with which Koch's name is almost as closely associated as Pasteur's, it is advisable again to remember that this is a question of facts and not of individuals ; that to us Gaul and Teuton are alike friends, as we fortunately keep no watch on the Rhine ; IO2 that neither Pasteur's brilliant work on fermentation, nor Koch's services on anthrax and tuberculosis ; neither the unreasoning enthusiasm of the French for Pasteur, nor the intelligent confidence of the Germans in Koch ; neither the grandiose egotism and artful dodging of the former, nor the apparent personal rancor of the latter ; none of these may obscure our vision in estimating the value of present evidence. Pasteur's theory may be briefly stated as follows : Since anthrax does not recur in the same individual, im- munity against it as against other infectious diseases may be secured by one attack ; the same effect may be ob- tained as in the variola of the human subject, by a harm- less inoculation with the specific virus after exposure to unusual influences whereby its effect upon the animal is diminished. To this theory Koch remarks that although some of the infectious diseases occur in the same animal but once, as a rule, yet no immunity is secured from others by the first attack ; and adduces erysipelas, the septic dis-. eases, gonorrhoea, intermittent fever, and recurrent fever, as examples familiar to all ; the last-named is especially interesting, because it is invariably associated with a specific bacterial form the spirochaete of Obermeier though final proof of the causal relation of the parasite has not yet been furnished. But more than that : Koch points out, by the records of Prussian veterinary surgeons, that anthrax itself not infrequently occurs twice in the same individual ; instances Oemler, who experimented on about one hundred animals years before Pasteur be- gan to work upon the subject ; and who saw horses, for instance, exhibit all the symptoms of anthrax once, twice, even eight times at intervals of weeks or months, after inoculation with anthrax material'; quotes Jarnowsky, who saw the disease occur among fifty human patients, twice in one at an interval of two years ; three times in another at intervals of two and three years. Loffler found that, of 52 rats which were inoculated at intervals of some days or weeks, with the fresh virus, 30 survived the 103 first, 23 the second, 13 the third, 3 the fourth, and i the fifth and sixth inoculation. Koch reminds Pasteur, there- fore, that even though an animal survive a virulent in- oculation he is not thereby secure against subsequent infection with anthrax. Further, Koch calls attention to the fact proven by himself and others that immunity against subcutaneous inoculation is not necessarily syn- onymous with immunity against infection through mucous membranes, especially of the alimentary canal ; although Koch admits that as the fact had been proven only for horses, dogs, mice, rats, and rabbits, it might be other- wise with regard to sheep, with which he had not at that time experimented. Such were the considerations advanced on either side. Pasteur's theory was soon extensively tested in Prus- sia and Hungary the experiment was superintended by an official commission of medical officers of the govern- ment. The .proceeding has been usually the same. Pas- teur vaccinates first with a weak virus, two weeks later with a stronger one, and after two further weeks, the animal is considered protected ; and those thus protected, as well as others not vaccinated, are inoculated with ma- terial fresh from an animal dead of anthrax. At the end of the experiment in Hungary, fourteen per cent, of the protected animals were dead mostly in consequence of the second protective vaccination ; ninety-four per cent, of the non-vaccinated died. In Prussia the result was more favorable : 3 out of 25 sheep (twelve per cent.) died after the second protective vaccination. After the final in- oculation with fresh blood, all of the non-vaccinated, but not one of the vaccinated, died. Pasteur thus demon- strated that sheep at least may acquire increased power of resistance to subcutaneous inoculation with anthrax ; but he demonstrated at the same time that his protective vaccination destroyed almost as large a per cent, of animals as usually die from spontaneous infection in the pasture. Since that time Pasteur seems to have em- ployed less virulent material, for according to accounts in French journals the mortality from the protective vac- IO4 cination has been often only three, two, one, or even less per cent. But as Koch very properly observes, the ability of an animal to withstand a mild inoculation is not the question at issue, for that has been long known ; the subsequent power to resist virulent material is the mooted point. The effect of Pasteur's own virus seems by no means uniform, since Duclaux, his assistant, who probably had virus of the proper attenuation, lost 20 out of 80 sheep in one flock during the two weeks after pro- tective vaccination, and 1 1 out of 60 in another ; yet in a third flock of the same race he lost only i out of 50. In the session of the Paris Veterinary Society, June 8, 1882, it was announced by Weber that 23 out of 993 sheep (2.3 per cent.) had succumbed to the preventive inoculation ; at a later session Mathieu reported 29 deaths among 896 vaccinations (3.2 per cent.). At Salz- dahlum 2 of 82 sheep died of anthrax after the second vaccination ; in Kapuwar 5 of 50, and in Packisch (as already stated) 3 out of 25. Oemler lost 26 among 703 (3.7 per cent.). Dr. Klein recently called the attention of the British Government to the fact that Pasteur's vac- cine virus was on sale in England ; that he (Klein) had found that even the first and weaker virus could kill animals, having himself lost two sheep by such vaccina- tion. Pasteur replies that Klein must have allowed other bacteria to invade the anthrax liquid. From these accounts it would appear that Pasteur's preventive inoculation is a somewhat perilous perform- ance, since even when performed by his own assistants it has killed 10, 12, even 25 per cent, of the vaccinated animals. Yet Pasteur recently stated that of nearly eighty thousand sheep vaccinated in France during the past year or two, none had died of the preventive inocula- tion. And now for the second question : Does Pasteur's vaccination protect the sheep which survive it against anthrax ? Against subcutaneous inoculation it certainly does for some weeks, as demonstrated in Prussia and Hungary ; how long this protection endures and more 105 important still economically whether it protects against infection through the mouth and alimentary canal, the usual mode of infection in the spontaneous anthrax of the pastures these questions are not yet decisively answered. Yet we have already some data, collected largely by Pasteur on the one side, and by Koch on the other. Boutet reports that in the department Eure-et- Loire (where anthrax is especially prevalent, according to Pasteur) the general mortality last year was three per cent. ; while of 79,392 vaccinated animals only . 7 per cent, died ; one herd of 2,308 vaccinated sheep lost only 8, less than .4 per cent.; another of 1,659 unvaccinated animals ex- posed to the same conditions lost 60 (3.6 percent.). Nocard vaccinated in August, 1881, 380 sheep, reserving 140 for comparison ; during the following five months 4 of the former and 15 of the latter died of spontaneous anthrax. According to these reports, therefore, the mor- tality of the vaccinated is only about one- tenth that of the unvaccinated animals, though it must be remembered that this does not include the mortality from the vaccina- tion itself. Other results are decidedly less favorable. Of 266 sheep vaccinated in Packisch last spring by Pasteur's assist- ant, Thuillier, there died between May and November, of spontaneous anthrax, 4 ; of 243 unvaccinated kept for comparison, 8. Cagny reported to the Paris Veterinary Society the following observation : In 1881, 20 sheep were vaccinated a la Pasteur ; in February, 1882, 10 more. They belonged to a herd of 250, 2 of which died of spontaneous anthrax in May and June, 1882 ; it was therefore deemed advisable to revaccinate, which was done in July with Pasteur's stronger virus. Of the 20 animals vaccinated in 1881, none died of this inoculation ; but of the 10 vaccinated only five months previously, nine died ; of 4 non-vaccinated animals inoculated for comparison at the same time, 3 died. Koch vaccinated 8 sheep after Pasteur's method, and then inoculated them with virulent material ; one died. The remaining 7 had therefore been inoculated with anthrax three times, 5* io6 Twelve days later material containing anthrax spores was mixed with their food ; 2 of the 7 died of anthrax. A review of the evidence already adduced indicates that although Pasteur's theory has been demolished be- yond repair, yet he has established the fact that the sus- ceptibility of sheep to anthrax can be diminished by vaccination with the cultivated bacilli. From the eco- nomic standpoint the value of this measure is still de- batable, though the aspect of the question has certainly improved since 1881, when the Hungarian medical com- mission, after inspecting Pasteur's experiment, advised their government not only to withhold its official sanction, but also to forbid all private experimentation. Nocard and Mollereau claim to have secured immunity of guinea- pigs by their method with oxygenated water ; Chauveau with heated anthrax blood. If these claims be substan- tiated we may hope that simple dilution may furnish a virus which shall protect against other diseases as well as against anthrax. At any rate, Pasteur has established a principle, and it is to be hoped will be merely stimulated by the present unsatisfactory results to future and more successful efforts for its application. Having thus sketched the present state of knowledge as to the agency of micro-organisms in the induction of disease, I may be permitted to consider briefly certain deductions therefrom, collectively known as the germ theory. I would emphasize the remark that the facts already summarized are not to be confounded with the speculations in which it may please one or another of us to indulge. Ocular demonstration removes a chain of events from the realm of speculation to the domain of fact ; hence the germ theory has no longer jurisdiction over anthrax at least. A possible future demonstration that small-pox, syphilis, etc., are not caused by micro- organisms would be disastrous to the germ theory, but could not change the facts already established as to the morbid agency of the bacillus anthracis. The germ theory supposes, if I understand it aright, that all infectious diseases are caused by the vital activity of parasitic organisms. In support of this theory there is certainly strong presumptive evidence : the stage of incubation ; the unlimited reproductive power of the virus ; the cyclical course and self-limitation of the dis- ease. The stage of incubation can be explained by the assumption of no unorganized virus ; all mere chemical compounds with which we are acquainted, even the fer- ments ptyalin and pepsin, begin to manifest the charac- teristic effects as soon as absorption has occurred. Panum found that even boiled putrid materials, i.e., the products of bacterial activity, though inducing the other features of septicaemia, failed to exhibit this charac- teristic incubation. By assuming an organism as the in- fecting agent this phenomenon becomes intelligible : the stage of incubation is then the period during which the inducted organisms are multiplying. In this way, too, the various durations of the incubative stage character- istic of the different diseases become intelligible. We cannot conceive that one chemical poison should require two to four days for the manifestation of its constitu- tional effects, as in scarlet fever, another forty days, as in syphilis ; but we know that different micro-organisms multiply with different degrees of rapidity. A micro- coccus may produce a second in thirty minutes ; the ba- cillus anthracis may accomplish its entire vital cycle in twenty-four hours ; the bacillus tuberculosis seems to require days. The unlimited reproductive power of the virus, characteristic of many infectious diseases, cannot be attributed to an unorganized poison or even organic ferment. A drop of blood from an animal poisoned with opium or strychnine exhibits only the power of the di- luted poison. A drop of vaccine lymph, of variolous or gonorrhoeal pus induces, in successive generations, un- limited quantities of identical materials. This effect cannot be justly ascribed even to any physiological unor- ganized ferment a favorite refuge of those who are determined to deny to bacteria any influence whatever. Ptyalin can, it is true, convert into grape-sugar many times its bulk of starch, and the ptyalin is not thereby io8 diminished in quantity ; but it is not increased. No more perfect illustration of this principle can be furnished than an experiment of Rosenberger, which has especial value because this observer would assign to bacteria a subordi- nate role in morbid processes. He found that the boiled blood and tissues of septic animals proven to contain no living bacteria induced septicaemia as certainly as the same blood unboiled. He then placed in one of two flasks containing identical culture-liquids a few drops of the boiled blood, and in the other the same quantity of unboiled blood. Two days later every drop out of the latter flask conveyed septic infection, while large quanti- ties from the former induced no reaction ; every drop of the septic fluid was swarming with bacteria ; in the other flask there were no organisms. The virus of an infectious disease must then be some- thing capable of reproduction, and this power is the pe- culiar characteristic of an organism. No unorganized poison, acid, salt, alkaloid, ferment is at present known which is capable of manifesting the phenomena shown by the virus of syphilis, variola, scarlatina, etc. Turning to diseases whose parasitic origin is already demonstrated, we find all the characteristics of the in- fectious diseases exquisitely exemplified. Anthrax is marked by a stage of incubation twelve to seventy hours during which the bacilli multiply and effect ac- cess to the blood ; the onset of constitutional disturbance is marked by the presence of numerous bacteria ; with the death and disappearance of these, convalescence be- gins ; the disease is eminently communicable by contact and yet may occur also sporadically and epidemically. And this leads me to mention a fact often urged as an objection to the parasite theory : that many infectious diseases are intimately associated with climate, soil, and topographical features, indeed indigenous to certain dis- tricts. This is, in fact, strongly favorable to the germ theory. Many plants and animals of larger growth have decidedly limited habitats ; botanists and zoologists have long since informed us that this same principle applies log to microscopic organisms, including fungi ; shall bacteria then, a family of fungi, be exceptions to the general rule ? As to anthrax, the case is answered ; the disease is endemic in certain districts, that is, the bacilli grow out- side of the animal body only in these districts. Koch has recently endeavored to elucidate the reasons for this. He ascertained that the growth of the anthrax bacilli re- quires moisture and a temperature of 15 C. It is evi- dent, therefore, why anthrax is not endemic in districts whose surface temperature fails to reach this point. Koch further ascertained, from the official reports of Prussian veterinary surgeons, that after the overflow of rivers and lakes an outbreak of anthrax had been frequently observed in cattle pasturing at certain points along the banks. He found by experiment that the bacilli flourish in infusions of various grasses, grains, and vegetables. Hay infusion is usually a poor soil, be- cause of acid reaction ; when rendered neutral or slightly alkaline, the bacilli grow in it luxuriantly ; but it had been long before stated by German and French observ- ers that the anthrax districts usually had a calcareous soil. Hence he conjectures that in such districts the alkalinity due to the lime may render even hay a soil favorable to the anthrax parasite ; that it may usually grow on decaying plants in such districts. That anthrax is especially prevalent in autumn seems to result in part at least from the fact that these bacilli, like many other fungi, grow only on dead plants. It might be interesting to review for comparison with anthrax the facts which establish the association of various infectious diseases cholera, yellow fever, the malarial fevers, for example with local influences of soil and temperature ; the ori- gin of typhoid fever in particular wells and springs, as has been conclusively established by observations upon the German and Austrian soldiery. Yet such discussion would transcend my time and my province, since I have attempted to portray what has been, not what remains to be accomplished. Certain popular arguments against the morbid agency 110 of bacteria are worthy of consideration perhaps, though not because of their intrinsic weight. To some it is in- credible that bacteria should harm us, since we live in health though surrounded by them eating, drinking, and breathing them. If it be remembered, however, that the name bacteria is merely a convenience for designating organisms of widely different functions, this argument seems less formidable. On the same principle it might be asserted that all mammalia are harmless because we come into daily contact with sheep, cattle, horses without injury. The diversity in function, food, etc., among the microscopic beings is not less marked than among the larger organisms : there are bacteria, and bacteria. It is surprising that Mr. Cheyne, in his admirable work on antiseptic sur- gery, falls into a similar error. He admits that bac- teria are not infrequently found under Mr. Lister's own dressings ; that sometimes the course of the wound appears thereby unaffected, .while at other times he thinks he has observed that the wounds heal less kindly. He consoles himself, however, with the reflection that these are " only micrococci." He seems to forget that several species of micrococci are distinguishable in form, size, color, and function from one another and from all others. The fact that certain micrococci found during different diseases are morphologically indistinguishable from others found under Mr. Lister's dressings, does not justify the assumption that all are functionally identical. If Mr. Cheyne were requested to swallow some pills, he would probably inquire as to their contents before com- plying, and would not be satisfied with the assurance that they were " only pills." Yet we have every reason for asserting that the minute globules known collectively as micrococci present differences as great as the larger globules designated, for convenience, pills. When we reflect that the active agents in the induction of pyaemia are micrococci ; that the organisms found in malignant diphtheria are micrococci, we must protest against Mr. Cheyne' s promiscuous ascription of benign qualities to Ill any tribe of bacteria, even if " only micrococci." There are micrococci and micrococci. Again, it is said, how is it possible for recovery to oc- cur from a disease caused by bacteria ? What stops their growth ? So far as I am aware, this question has not been decisively answered. Several facts suggest that the products of their own vital activity arrest further de- velopment. Analogous facts have been demonstrated : the mucoj racemosus ceases to grow in a liquid when the alcohol produced by its own vital action exceeds a certain percentage, though there may still remain fer- mentable sugar in abundance. During putrefaction there are produced numerous compounds, of which one at least, carbolic acid, arrests, even in small quantities, further development of putrefactive bacteria. Brieger has recently shown that the infectious diseases proven clinically and experimentally to be caused by putrid in- fection pyaemia, diphtheria, erysipelas are distin- guished by the excretion in the urine of excessive quan- tities of carbolic acid ; while in other diseases exhibiting equally intense fever and constitutional disturbance acute rheumatism and variola, for example the amount of this acid in the urine is normal or subnormal. Hence the conjecture that the bacteria are both bane and anti- dote. Yet a failure to explain the phenomena satisfac- torily does not, of course, impair the stability of the fact. The bacilli of anthrax are observed to become, in the living animal, pale, of uneven outline, incapable of ab- sorbing staining fluids ; in short, they are dead. With their death the convalescence of the host begins, as a rule. It should be remembered that other parasites than bac- teria may cause disease, some of them, perhaps, over- looked in the universal hunt .after bacteria. Koch calls attention to Woronin's discovery that a disease of cab- bages is caused by an amoeboid parasite, which enters the root of the plant and becomes almost indistinguishable from the proper vegetable cells ; and suggests the possi- bility that some of the amoeboid bodies known as white 112 blood-corpuscles in animals may be intruding organisms, especially since Ehrlich has shown that different leuco- cytes exhibit various reactions to staining agents. Five years ago it was discovered that a mould-fungus, the ac- tinomyces, induces fatal disease of man and other ani- mals ; Wittich found organisms, which he calls spirilla, in the blood of apparently healthy gophers ; Koch found numerous organisms (monads) in the blood of five gophers that had died without other discoverable cause. A new filaria has been recently discovered in the human subject by Bastian, and similar discoveries are reported in the camel and the hog. There is probably no one among us who doubts that the trichina spiralis can and does induce in the human subject a serious, even fatal disease ; yet the evidence as yet adduced is merely the association of the worm with the morbid condition, for no one, so far as I am aware, has ever induced the disease by introduction of the iso- lated worms. Yet the same men who assert the patho- genetic influence of the trichina, contemptuously reject the idea that leprosy, tuberculosis, recurrent fever, and pyaemia are caused by bacteria, although the evidence constant association of the parasite with the morbid con- dition, applies to all cases. Indeed, the weight of evi- dence is decidedly in favor of the bacteria ; for the tri- china is found not only in the subjects of trichinosis, but also in many individuals who have never been sus- pected of harboring the worm. It is not extremely sel- dom that trichinae are found in the bodies of patients who have died of acute disease, wounds, accidents, etc.; in- deed, an examination of several thousand consecutive cadavers in German hospitals, some years ago, revealed trichinae in over two per cent., without regard to the cause of death. It might, therefore be argued that the presence of the worm is a mere accident an epiphenom- enon, observed in healthy as well as in diseased con- ditions. The bacilli of leprosy, on the other hand, are found only in patients suffering from this disease. I would not express any doubt, by this comparison, of the morbid agency of the trichina, but would merely call atten- tion to the fact that for this belief we have really no more conclusive evidence than we have for accepting the path- ogenetic influence of bacteria in leprosy and in several other diseases. Yet it will doubtless be years before some of us realize the fact that in this unreasoning and prejudiced opposition to demonstrated facts, we are play- ing the unenviable role of the cow to the locomotive of advancing science. George Stephenson's prophecy that the result of such collision would be "bad for the con" has been often fulfilled; neither horned cattle nor pseudo-bacilli have materially retarded the progress of science. The improvement of means and methods for minute investigation has ever been and must still be followed by further advance into the realm of the minute, whose boundaries doubtless stretch far beyond the pres- ent means of optical exploration. After centuries of controversy the intestinal worms banished the " ver- micular diathesis ;" the acarus scabiei conquered the " itch cachexia ;" the step from the acarus to the bacil- lus tuberculosis is not quantitatively greater than from the tape-worm to the acarus ; each is merely the measure of successive improvements in means for minute obser- vation. Yet the same spirit which nursed the vermicu- lar and itch diatheses, will doubtless for years see in bacteria only fibrin threads and fat crystals ; and will cling with heroic devotion to the tubercular diathesis, to "micro-necrosis," and to narrow lymph-spaces. When we glance over the progress of the last few years ; when we consider the life-saving revolution in surgical methods ; when we regard the enhancement, in- deed the very salvation of enormous economic interests by the eradication of the bacterial disease of silkworms, without mentioning preventive vaccination against anthrax and chicken-cholera, we may search in vain the records of other departments of science during the same period for discoveries which have secured direct personal and pecuniary advantages comparable to those derived from our present incomplete knowledge of the relations of mi- H4 cro-organisms to disease. And when we consider the problems already half solved, the questions to whose so- lution the way appears open through the same methods already successfully applied to anthrax and tuberculosis, we may hope for results to which present knowledge shall seem a mere introduction. But these results can be secured only by earnest, skilful, continuous experi- mental investigation, which is practically impossible with- out pecuniary support. In France and Germany such support is liberally supplied by the government ; in the United States, where human life is certainly as valuable as there ; where live-stock interests are already greater than in these countries combined, and must multiply many fold in the immediate future ; where a single infec- tious disease of cattle has caused the loss of $20,000,000 in one year, and a single disease of hogs the destruction of $30,000,000 in the same time: where infectious dis- eases are so prevalent among live stock that the fear of infection has closed European markets against American meat and cattle the government of this great common- wealth, which advances enormous sums for local river and harbor improvements ; which sends expensive com- missions over the world to observe the transit of Venus or of the moon ; to find an open Polar sea ; and engages in other undertakings of purely scientific interest, has not yet made on.e judicious, systematic, liberally supported inquiry into the possibility of acquiring protection against pleuro-pneumonia, hog-cholera, and other de- vourers of the national wealth. A glance at the Im- perial German Health Bureau and its work during the last four years, and a mental comparison of the pecu- niary resources of Germany with those of the United States, inspire the hope that we shall not always lag so far behind in matters which appeal to the tenderest spot of the American anatomy the pocket. In concluding these lectures, Mr. President and gen- tlemen, I shall offer no apology for their fragmentary character, since I would not call attention to defects al- ready amply apparent. Yet I venture to hope that one 115 merit may be accorded them that they constitute an impartial and un partisan attempt to portray the present status of this vexed question. And this I hope, not on personal grounds, but because a suspicion of insincerity in the portrayal would retard acquiescence in what I must and do regard as truth. If these lectures shall serve as a vehicle for conveying to the busy practitioner facts which he has not time to seek amid the mass of current literature ; shall contri- bute, however little, to the more general discrimination between theories and facts, between observations and deductions, between assertions and demonstrations ; shall tend to confirm the belief that much may be hoped for, though perhaps but little is already completed in this direction their object will be accomplished, and your lecturer will hope that he was not inexcusably presump- tuous in consenting to appear upon a platform which has been honored by a Bartholow and by a Dalton. APPENDIX A. The following cuts are copied from some of the twenty- eight photomicrographs exhibited at the lectures. It has been deemed advisable to print them here with the brief- est possible summary of the remarks which accompanied their exhibition. In erysipelas the lymph-spaces just at and in front of the advancing edge of the inflamed area contain micro- cocci. These organisms have been isolated by cultiva- tion on solid media (Koch's method) by Fehleisen. He reports the successful induction of erysipelas by inocu- lation with the micrococci thus isolated, in eight rabbits and in one human patient. Recurrent or relapsing fever is characterized by the presence of Obermeier's spirillum in the blood. As yet no successful inoculation with the isolated spi- rilla has been reported. A short, thick bacillus is found post-mortem in the liver, kidney, spleen, and lymph-glands in the majority of cases of typhoid fever (Eberth, Koch, Friedlander) ; and larger bacilli in the vicinity of the intestinal ulcers (Klebs). Maragliano asserts the presence of both vari- eties in blood drawn by a hypodermic syringe from the spleen in fifteen cases (intra vitam). It would seem, however, that he protests too much ; for even post-mor- tem only Eberth' s, never Klebs' bacilli, are found in the spleen. In croupous pneumonia small bacteria have been found at the edge of the advancing inflammation (like the micrococci in erysipelas ) ; also in some internal or- gans. The same bacteria have been found in the lung immediately post-mortem, and even intra vitam. Endocarditis ulcerosa seems to be one of the forms of pyaemia, sometimes of spontaneous (i.e., undiscovered) origin. The internal organs as well as the cutaneous tubercles of patients afflicted with leprosy contain a distinct bac- terium the bacillus leprae. Attempts to induce the disease in the lower animals by inoculation with the iso- lated bacilli as well as with leprous tissue, have not as yet been successful. Frisch, of Vienna, has found a characteristic short, -, Fig. 9. Skin excised, intra vitam, from a case ot erysipelas; micrococci in lymph-vessel, x 700. (Koch.) thick bacillus in every case of rhinoscleroma (twelve in number) which he has had opportunity to examine. Pieces were excised from the nose or mouth intra vitam ; the bacilli occur, like those of leprosy, in the large cells characteristic of the tissue. Frisch cultivated these or- ganisms on solid media, after Koch ; but was unsuc- cessful in attempts to induce the disease in rabbits. It must be remembered that man is the only animal known to suffer from rhinoscleroma and from leprosy. Klebs and Crudeli assert the induction of malarial fe- ver in rabbits through the agency of a bacterium the bacillus malaria. Dr. Sternberg, U. S. A., has made a critical and experimental review of this work, from which f \ Fig. io. Spirochaete of Obermeier and human blood-corpuscles, x 700. (Koch.) he concludes : " The evidence upon which Klebs and Crudeli have based the claim of the discovery of a ba- cillus malarias cannot be accepted as sufficient," and " their conclusions are shown not to be well-founded." Such is the general opinion, so far as I have been able to ascertain, among those familiar with this department of investigation. Bacteria said to be identical with these 119 have been found in the blood of patients suffering from malarial fever, and by Ziehl in one individual who had no symptoms nor history of intermittent fever, but was suffering from diabetes. In three of Ziehl' s four cases, the bacilli disappeared from the blood after the adminis- tration of quinine for several days. Bacteria of various kinds have been seen in syphilitic Fig. ii. Kidney, typhoid fever ; masses of bacilli in intertubular capillaries, x loo. (Koch.) tissues, post-mortem, by different observers. Quite re- cently Birch-Hirschfeld announced the discovery of micrococci in twelve gummata, post-mortem ; in three condylomata, one 'chancre, and one cutaneous papule excised during life. Morison, using aniline staining and Abbe illuminator, found bacilli in chancres and other syphilitic tissues the same variety being present in all. 120 The contents of variolous pustules, like other pus often contains micrococci. No trustworthy observation of the presence of bacteria in the blood during this disease has been recorded. Ehrlich has sought them in vain even in hernorrhagic small-pox. Post-mortem they are some- times found in the tissues. Fig. 12. Edge of bacterial colony in the liver from typhoid fever ; the indi- vidual bacilli are seen, x 700. (Koch.) In diphtheria micrococci are often found not only in the local necrotic tissue, but also in internal organs and in the blood. In scarlatina no reliable affirmative ob- servations have been made, so far as I am aware. But since diphtheria, scarlatina, and erysipelas must be classed according to clinical, experimental, and chemical (Brieger) evidence with the putrid diseases, the evidence in favor 121 of the bacterial origin of septicaemia and pyaemia suggests analogous etiological influences for these diseases also. Schiitz and Lofner have recently reported the induc- tion of glanders in rabbits and in two horses by inocula- tion with bacilli isolated by cultivation from animals suf- fering from this disease. Fig. 13. Intertubular capillary of kidney containing bacteria ; from a case of croupous pneumonia, x 700. (Koch.) Cuts of the trichina spiralis and of the filaria san- guinis are added as an illustration of the fact that morphological similarity does not prove physiological identity. These two nematode worms are, of course, easily distinguishable by the difference in size ; yet structurally they are, in the larval state as here repre- sented, quite similar. Yet the one is found coiled in the 6 122 voluntary muscles, its migration from the intestine often causing symptoms simulating typhoid fever ; the filaria, on the other hand, circulates with the blood (by night only, as a rule), and is associated with one of several morbid states chyluria, lymph-scrotum, sometimes end- ing in pyaemia (as in the case which I was fortunate enough to observe in the London Hospital). ' In some Fig. 14. Incipient abscess formation around a vessel occluded by a micrococ- cus colony. Heart-muscle, endocarditis ulcerosa, x 100. (Koch.) cases its presence seems to cause no abnormal symp- toms. One of the most interesting of recent observations is that of Brieger and Ehrlich (Berliner Klin. Wochens- chrift, 44, 1882), in which they report two cases of Koch's " malignant cedema" in human subjects suffering 123 Fig. 15. Micrococci in renal capillary, small-pox, x 700. (Koch.) Fig. 1 6. Trichina spiralis, x 50. (Oliver.) 124 Fig. 17. | ilana sangumis hominis in human blood, X28o. (In this case from twenty-five to one hundred worms were found in every drop of blood between six P.M. and five A.M.) Fig. 18. Filaria, dried and stained to show the sheath (compare Fig. 16). 125 from typhoid fever. The bacillus characteristic of this affection is widely distributed, being often found in or- dinary garden earth, and frequently appearing in animal bodies a few hours after death ; in these two cases the organisms seem to have been introduced by subcutaneous injections of musk. Koch and Pasteur have induced the disease in mice and rabbits by inoculation with earth and with the isolated bacilli ; and the morbid condition which often appears spontaneously in cattle, termed charbon symptomatique, or Rauschbrand, seems to be the same disease : but this is, I believe, the first instance in which the bacterium has been demonstrated in the human subject ot the disease. 126 APPENDIX B. A sketch of methods especially adapted to the detec- tion and recognition of bacteria is added. The basic aniline pigments Bismarck brown, genti- ana violet, methyl blue and violet, and fuchsin are especially valuable for this purpose, because readily ab- sorbed and retained by bacteria (Weigert). These may be kept as simple filtered solutions (one to two per cent.) in distilled water, though the addition of a little alcohol (ten per cent.) is desirable to secure permanence and to prevent the growth of bacteria in the liquid a possible source of error which must be always borne in mind. Sections may be prepared from fresh or from hardened tissues, but must be thin, in order to permit satisfactory inspection of these minute objects ; a microtome is therefore an extremely desirable, indeed almost essential, means for the preparation of such sections. For harden- ing tissues absolute alcohol should be used ; small pieces cubes not more than one-half or three-fourths of an inch in each dimension, for example are sufficiently hard after immersion for one or two days in several (four or five) ounces each of alcohol. After immersion for three to ten minutes in the two per cent, aqueous solution of the aniline color, a section exhibits an intense, diffused staining; it is then trans- ferred for a few minutes to alcohol, which abstracts the color from all morphological elements (with certain oc- casional exceptions) except the nuclei of cells, and bac- teria ; it is usually desirable to transfer the sections to a second and even a third dish of alcohol, in order to wash off the coloring matter dissolved out of the section by the alcohol in the first dish. For permanent preserva- tion the sections should be passed through oil of cloves and mounted in Canada balsam after the usual method ; 127 for temporsny inspection they may be laid in glycerine after washing with distilled water ; but all except the brown colors gradually fade in glycerine. Bismarck brown is .for this reason, as well as for the cleanness of its staining i.e., absence of granular precipitate per- haps the most satisfactory for general use ; though in special cases (tubercle bacilli and gonorrhoeal micrococci for example) the blue and the red pigments are pre- ferable. The violet (methyl and gentiana) dyes are especially useful in the detection of amyloid degeneration ; for while the normal elements are colored blue, those which have undergone the amyloid change exhibit an intense red color. This red tint rapidly disappears if the sec- tions are placed in alcohol ; hence they cannot be mounted in balsam, but may be kept (a certain time) in glycerine. Bacteria which may be present in sections stained in this way can be usually recognized at once (especially when occurring in groups) by their intense color ; yet their detection can be facilitated by taking advantage ot the fact that these organisms not only absorb the aniline colors readily, but retain these colors in the presence of reagents which decolorize the other morphological ele- ments that may be present : after exposure to such agents, therefore, the bacteria are distinguishable at once as the only intensely stained objects in the field. Occa- sionally other objects than bacteria are encountered which exhibit the same reaction the plasma-cells of Ehrlich, nuclear detritus, globules of leucine. Ehrlich's cells, moreover, simulate groups of micrococci some- what closely, but can be usually distinguished by the following characteristics : i, the granules of these cells are rarely of uniform size, while the micrococci of a zoogloea mass are ; 2, the granules composing the cell usually surround a clear, oval space probably the location of the nucleus ; no such appearance is pre- sented by a group of micrococci ; 3, numerous plasma- cells presenting a uniform appearance usually occur in 128 the same section, even in the same field; they are seen not infrequently in tissues in a state of chronic in- flammation. Any one of several agents may be employed for this purpose of differentiating bacteria from surrounding ob- jects by decolorizing the latter; simple immersion in alcohol or ether for some minutes sometimes accom- plishes this result. The preferable agents are, however, 1, a solution of acetic acid (two to five per cent.), and, 2, a solution of the carbonate of potassium (one to three per cent.) in water. Immersion of the stained sections in one of these fluids for five to ten minutes usually suf- fices to decolorize the morphological elements other than bacteria, while the latter still retain a brilliant color. It must be remembered, however, that none of these rules is of universal application : different varieties of bacteria exhibit various reactions toward these agents, and some of the aniline dyes are less readily extracted from the nuclei than others ; the blue and the violet are, in my experience, more tractable in this regard than the brown colors. When it is intended to differentiate in this manner the sections should be at first intensely stained, which may be accomplished by the use of stronger aniline solutions, or (preferably) by permitting them to lie for a longer time in the ordinary (two per cent.) solution. The prominence of these colored bodies is further enhanced by illumination with the Abbe condenser, whereby refraction outlines are practically obliterated, the colored objects appearing alone simply by virtue of their color against a white background. While the cutting of sections requires time and skill not usually possessed by the general practitioner, the preparation of liquids blood, pus, sputum- for the de- tection of bacteria is extremely simple, and can be accomplished without special knowledge, skill, or appar- atus. This is particularly fortunate, since a valuable means for clinical diagnosis is thereby brought within the reach of every one who possesses a microscope, even an 129 inexpensive one. The points to be secured are : first, a very thin layer of the liquid under examination, and, second, the coagulation of the albuminous constituents of that liquid. A drop, a very small drop of pus, sputum, or blood is placed in the middle of a clean cover-glass ; a second cover-glass is then laid upon this and the two are pressed gently together until the enclosed drop has become a very thin layer ; the two cover-glasses are then separated by sliding one over the other, not by pulling them apart. The two glasses, each of which has now a thin layer upon its surface, are allowed to dry,; the co- agulation of the albumen of the fluid (a most important measure, which prevents precipitation of granules from the staining fluid) is now accomplished by holding the cover-glass over a gas or alcohol flame until it acquires such a temperature as to be unpleasantly warm when applied to the skin ; or the glass may be " passed three times through the Bunsen flame," as directed by Ehrlich. The pus or sputum is now stained either by floating the cover-glass on the staining liquid, or (more conveniently) by pouring a few drops of the aniline solution from a pipette onto the cover-glass ; after five to fifteen minutes the staining fluid is poured off, the excess of color removed by washing in a stream of water ; the cover- glass is now allowed to dry and is then ready for mount- ing in either glycerine or balsam. The methylene blue is perhaps the most satisfactory of the aniline colors for general use in staining these dry cover-glass prep- arations. While most species of bacteria known to occur in human tissues are readily stained by these methods, certain varieties require special modifications thereof. Piominent among these is the bacillus found in tubercu- lous tissues, whose presence in sputum already possesses diagnostic (and prognostic ?) value. Of the various methods already published for staining the bacillus tu- berculosis, Ehrlich's has the general preference, and has always given satisfactory results in the writer's hands. This method requires (a) a saturated solution of aniline 130 oil in water, 1 made by adding the oil, drop by drop, to distilled water in a test-tube, which is meanwhile con- stantly shaken ; upon saturation, indicated by turbidity, the mixture is filtered. To the clear filtrate are added a few drops of (b) a saturated alcoholic solution of an ani- line pigment, preferably fuchsin. Upon the appearance of turbidity (or opalescence) the staining fluid is ready for use (though it is by some observers thought desirable to filter before using). In this liquid sections of tissue or layers of sputum on cover-glasses (prepared as already directed)lie twenty -four hours at ordinary temperatures, or thirty to sixty minutes if the temperature be main- tained at 50 C. At the end of this time all the ele- ments, bacilli included, are stained ; in order to differen- tiate the bacteria the section (or cover-glass) is immersed for a few seconds in a mixture of nitric acid (one part) and water (three parts). The color disappears at once, and after washing the section in water and mounting in the usual way, it will be found that the bacilli only ex- hibit a deep color, the other objects in the field having little or no color. The staining is now complete the red bacilli appearing against a white background ; yet a pleasing contrast may be obtained by coloring this back- ground blue ', this is easily accomplished by immersing the decolorized section or cover-glass in the ordinary two per cent, watery solution of methylene blue. The already stained tubercle bacilli (red) are unaffected by the second dye and retain the first color ; while nuclei, etc., absorb the second (blue) color only. The aniline oil should be fresh, for in time it becomes oxidized, a condition indicated by a dark instead of the original light brown hue ; in this condition the result of staining is uncertain. The bacilli are in some cases simulated in size and shape by minute crystals, but are, however, easily distinguished from the latter by the bril- liant red color which the true bacilli exhibit (when stained 1 Those who cannot conveniently procure the oil will find an excellent substitute in ordinary (pure) carbolic acid. The directions for use remain as above with the substitution of the words " carbolic acid " for " aniline oil." with fuchsin). To secure thorough staining of all ba- cilli present it is advisable to expose the section to the staining-fluid for twenty-four hours. Stained by this method the bacilli can be detected in sputum with an ordinarily good one-fifth inch objective (giving 250 to 300 diameters) and simple central illu- mination without condenser ; though for critical exami- nation, especially in tissues, higher powers (400 to 600 diameters) and special illumination are desirable. It is already demonstrated that the presence of these bacilli has decided diagnostic value, not only in sputum but also in pus from laryngeal ulcers, from cold abscesses, from joint cavities, and in urine. The bacilli of leprosy may be stained in fresh sections with the ordinary two per cent, aqueous solutions of the aniline colors, without special preparation ; if the tissue has been long exposed to alcohol it is desirable to place the sections for a few minutes in a five per cent, watery solution of acetic acid, and then transfer them to a ten per cent, solution of caustic potash. After washing in water they may be then stained with the ordinary fuchsin solution. The micrococci of gonorrhoeal pus require no special treatment ; the cover-glass on which the pus is dried and heated (as already directed) is treated for five to ten min- utes with the two per cent, solution of methylene blue. For cutting extremely thin sections of lung and other delicate tissues, the following method of imbedding is well adapted : 1 The tissue lies for twenty-four hours in the ordinary clearing solution (one part of carbolic acid and four of turpentine); it is then transferred for twenty- four hours to a saturated solution of paraffin in turpentine, after which it may be imbedded either in pure paraffin or in one of the many mixtures of this substance with tallow oil. 1 For a knowledge of this method, and of other valuable points in histological technique, I am indebted to the rare technical skill and extensive experience of my friend Dr. W. T. 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