•4 
 
 
 
 
hxcmangp: 
 
 JUN 
 
 1919 
 
 WAR DEAFNESS AND ITS 
 
 PREVENTION -REPORT OF THE 
 
 LABYRINTHS OF THE ANIMALS 
 
 USED IN TESTING OF 
 
 PREVENTIVE MEASURES. 
 
 (MIDDLE EARS PREVIOUSLY 
 
 REPORTED) 
 
 BY 
 
 STACY R. GUILD 
 
 From the Department of Anatomy, University of Michigan 
 Medical School, Ann Arbor, Michigan 
 
 A Dissertation Submitted in Partial Fulfillment of 
 
 the Requirements for the Degree of Doctor of 
 
 Philosophy in the University of Michigan 
 
 Reprint from 
 
 THE JOURNAL OF 
 
 LABORATORY AND CLINICAL MEDICINE 
 
 St. Louis 
 
 Vol. IV, No. 4, January, 1919 
 
 
■/ 
 
WAR DEAFNESS AND ITS PREVENTION— REPORT OF THE LABY- 
 RINTHS OF THE ANIMALS USED IN TESTING OF PREVENTIVE 
 MEASURES* (MIDDLE EARS PREVIOUSLY REPORTED)! 
 
 By Stacy R. Guild, Ann Arbor, Mich. 
 
 METHODS 
 
 A FULL description of the procedure by which each animal was handled at 
 the time of exposure to the detonations was given in the report of the 
 middle ear conditions; reference may be made to it for that part of the technic. 
 In that report the protective measures tested were also listed and described. 
 As stated there the animals were killed about 48 hours after exposure to the 
 detonations. The treatment of the tissues at the time of killing the animals 
 was directed primarily to the securing of the best possible cochlear fixation. 
 The method used was the one with which I had had the best results in a series 
 of experiments on cochlear histologic technic, conducted as a preliminary to 
 objective work on the physiology of hearing w^hich the war has postponed in- 
 definitely, but which I hope at some future time to carry out. The fixation 
 fluid used was Zenker- formol in the proportions suggested by Maximow (1909), 
 as a modification of Kelly's fluid, for other work. A stock solution is made in 
 the following proportions : 
 
 Mercuric bichloride, 50 gm. 
 
 Potassium dichromate, 25 gm. 
 
 Sodium sulphate, 10 gm. 
 
 Distilled water, 1000 c.c. 
 
 This was filtered carefully to exclude any particles which might block 
 small vessels. Just before using there was added to this stock solution 10 per 
 cent by volume of 10 per cent formalin; the glacial acetic acid of the regular 
 Zenker's fluid was not added. Both solutions were kept in an oven at 39 ■ C. 
 until the time of mixing for use. The fixative was injected through the vascular 
 system, following a thorough washing out with a 0.75 per cent solution of 
 sodium chloride, also kept at 39° C. until placed in tlie flask for injection. This 
 preliminary washing out is essential for the securing of good penetration of the 
 fixative. 
 
 *Submitted to the National Research Council. 
 
 From the Department of Anatomy, l^niversity of Michigan Medical School, Ann Arbor, Michigan. 
 
 tThree previous reports have been made; the first was published in this Journal. September, 
 1917; the second, January, 1918; and the third, ^Iarch, 1918. The second report is the one containing the 
 account of the middle ears the labyrinths of which are here reported. 
 
 392638 
 
The routing prucJL-Uyic ^wii j4>. jyiace the animal under chloroform anes- 
 thesia ; then to open the thorax and j^ericardial sac and insert the cannula of 
 the injecting apparatus in the systemic aorta through the wall of the left ven- 
 tricle, the ligature heing placed hy passing the thread through the transverse 
 sinus of the pericardium, thus including the pulmonary aorta. This can be done 
 very rapidly after a few trials and I was able regularly to have the saline solu- 
 tion running soon enough to avoid any clotting of blood in the cochlear vessels. 
 The vessels to the caudal half of the body were routinely clamped off by a hemo- 
 stat placed so as to include both aorta and inferior vena cava just above the 
 diaphragm. This reduced the amounl of fluid necessary for satisfactory injec- 
 tion of the cochlear region. The injection was made with air jiressurc averag- 
 ing 145 mm. of mercury. About 150 c.c. of warm saline srjiution were used 
 in washing out the blood and this was followed immediately by 200 c.c. of the 
 warm fixative described above. Only a small portion of this reaches the coch- 
 leae, of course, since all the blood vessels of the upper half of the body are in- 
 jected. The cochleae and some of the surrounding bone, including most of the 
 vestibular parts, were then removed and the two pieces placed in 50 c.c. of 
 <\arm fixing fluid and left at room temperature. These remained in the fix- 
 ing fluid from a week to ten days, the fluid being changed two or three times, 
 because a precipitate forms slowly after mixing the formalin with the Zenker 
 stock solution. They were then washed for 24 hours in running tap water and 
 placed in 10 per cent alcohol ; and were transferred from this to 80 per cent 
 alcohol by 10 per cent changes at 24 hour intervals. They were then placed in 
 80 per cent alcohol to which had been added a sufficient amount of a saturated 
 solution of iodine in absolute alcohol to make the mixture a clierrv red color. 
 In this they remained until they ceased to decolorize the solution, more iodine 
 being added as needed, 'i'his time averaged about ten days. They were then 
 passed at 24 hour intervals through 90 per cent and 95 per cent alcohol into 
 absolute alcohol which was changed three times. Instead of passing them di- 
 rectly into the mixture of equal parts of absolute alcohol and ether, they were 
 passed through four intermediate mixtures, each increasing the ether ratio 
 10 per cent until the 50 per cent was reached. This was an extra precaution to 
 avoid as far as possible shrinkages due to a more sudden change. Ordinarv 
 celloidin embedding followed, slow evaporation being used, taking a month or 
 more to reach a firm consistency. The blocks were then hardened in 80 per cent 
 alcohol and transferred through 50 per cent and 30 per cent alcohols into 4 per 
 cent nitric acid for decalcification. They remained in this 12 days, except two 
 groups, one of which remained 6 days and the other 9 days. The fluid was 
 changed daily. They were then transferred to a 5 i)er cent solution of sodium 
 sulphate, remaining in this 48 hours with one change of fluid; and were then 
 washed in running tap water for 24 hours. The blocks were then "double em- 
 bedded" in paraffin. They were passed from the tap water through 30. 50, 80, 
 and 95 per cent alcohols, and the dehydration completed with carbol-xylol (crys- 
 tal carbolic acid one part, xylol three parts). Aksolute alcohol can not be used 
 
because of the celloidin present. An intermediate step of equal parts oi 95 per 
 cent alcoliol and carbol-xylol was used to make the change more graduah After 
 dehydration with carbol-xylol they were changed to xykjl and while thus cleared 
 the blocks were trimmed in such a way that the position of the modiolar axis 
 could be determined later for orientation of the sectioning. They were in- 
 filtrated and embedded in 52° C. paraffin in the usual way, the celloidin block 
 containing the cochlea being handled as a piece of tissue. 
 
 This method gave in most cases a very fair preservation of the delicate 
 epithelial structures in the cochlea ; in a few instances it has failed, these are 
 probably cases where the vascular injection did not penetrate well. The pres- 
 ervation of the tectorial membrane is poor by this method, it is usually found 
 curled back in part of the turns, and it is not so thick as some methods show 
 it to be. 
 
 From blocks prepared by this method it is possible to cut thinner serial 
 sections than have usually been employed in studies on the cochlea. From such 
 a block I have an unbroken series of 5 micra sections of a whole guinea pig 
 cochlea, and I have cut some at 3 micra, but not a series. The material used 
 in this study is cut in 7 micra sections; because of the shortage of glassware, 
 especially of large cover-glasses, only every fifth section was saved. It would 
 have been impossible to mount all the series otherwise. From the wide extent 
 of the injured areas reported in the experiments of Wittmaack, Yoshii, and 
 others, it was thought that every fifth section would be sufficient to fully indi- 
 cate the extent of the injuries. For an exact study of the distribution of injury 
 that I have found unbroken series are needed ; every fifth section gives the 
 general distribution of injured areas, but the study of unbroken series might 
 yield additional facts of interest. The sectioning was done with a sliding micro- 
 tome, using the "water-on-the-knife" method. The blocks were oriented so as 
 to parallel the modiolus as nearly as possible in sectioning; in most cases this 
 was closely approximated, in a few there was some deviation. In^ mo5tt<sbIocks 
 the sectioning was continued until the stapes was reached ; in s^pif j^J^ was Mirced 
 to stop sooner either because of imperfect decalcification of t^iS. BlI)(^'\Di/ be- 
 cause of hard particles in the niche of the round windgvy^ (^r el-Sewhere^^ this 
 region ; these particles are probably grains of sand from fhe-tap-wsfrer, which 
 was unusually laden with dirt at the time part of the washing was done. The 
 sections were fixed to slides by the usual water-albumen paraffin section method, 
 and were stained with Heidenhain's iron lac hematoxylin ; counterstained with 
 benzopurpurin, and mounted in damar. The technic differed from the usual 
 treatment of paraffin sections on slides only in the use of carbol-xylol, instead 
 of absolute alcohol, in passing from xylol to 95 per cent alcohol and back again. 
 This was necessary because of the celloidin present. To completely remove 
 mercuric crystals the sections were passed through an iodine solution in 80 per 
 cent alcohol before the transference to iron alum. The benzopurpurin was used 
 in solution in 95 per cent alcohol ; the sections permitted to overstain, and the 
 excess stain removed by fresh 95 per cent alcohol ; the slides being transferred to 
 carbol-xylol to stop the decolorization at the desired stage. 
 
RESULTS 
 
 The condition oi tlic lain rintliinc parts, here reported, should he compared 
 with the middle ear conchtions, previously reported ; this can readily be done 
 for the individual cars, as the animal designation has been made in all tabulations. 
 
 The injuries to the inner car have been, for the most part at least, limited 
 to the cochlea. In no case were all of the special sensory areas in the vestibular 
 part of the labyrinth sectioned, owing to the close trimming of the blocks 
 neces.sary to save glassware. Of those sectioned, many of the macul.c 
 acusiicae and some of the crista; acustica? have some shrunken hair cells, but 
 I have no reason to believe that these are more than artefacts. The stapes 
 was reached in the sectioning in 76 of the 92 cochleae cut ; of the 76, all but 
 10 are in the normal position. In each of these ten cases the annular ligament 
 is broken and the base plate of the stapes tilted more or less into the vesti- 
 bule. While this condition may be due to the detonations, I am inclined to 
 believe that it was caused by accidents in handling at some time before the 
 celloidin embedding, most probably during the removal from the animal. 
 Therefore these displacements will not be considered further. In both ears 
 of one animal no joint cavity is present about the base plate of the stapes, but 
 this is not a condition which can be attributed to the detonation. The position 
 of the membrana tympani secundaria, closing the fenestra rotunda, is normal, or 
 nearly so, in all cases; it is slightly wavy in some, but no more so than the 
 changing fluids might account for. In part of the membranes there is some 
 edema evident, especially of the middle ear surface. Free blood cells and clots 
 are present on the middle ear surface, but these are the result of the damage to 
 the middle ear parts, already considered. None of the labyrinths have what 
 may be called "gross" lesions, such as the rupture of the walls of the ductus 
 cochlearis or the .scala vestibuli or the scala tympani. The occasional bending 
 of parts of the basilar membrane occurs as often in controls as in exposed ani- 
 mals, and is probably due to the eml)edding. Definite lesions of the organ of 
 Corti and of the spiral ganglion arc present in many of the cochleie. Xo evi- 
 dence of extensive internal hemorrhage was found in any of the labyrinths ; 
 in .some a few isolated blood cells were observed adhering to the scala tympani 
 surface of the basilar membrane. (See Figs. 10 and 13.) 
 
 To present the appearance of the lesions ob.served drawings will be used ; 
 they are selected to show the more usual types of injuries. 
 
 In speaking of the turns of the cochlea the method of designating by half- 
 turns, beginning at the basal end, has been selected as best adapted to the pur- 
 poses of this report. Fig. 1 shows in outline a modiolar section with the turns 
 numbered according to the method used. The part in the midmodiolar section 
 is considered as the middle of each half-turn; the junctions of the half-turns 
 have the organ of Corti cut tangentially. Such junctions may be .seen in Fig. 
 2. In speaking of sections of the organ of Corti the term "radial" refers to 
 those in the region of the modiolar sections; the term "tangential" refers to 
 sections in the region of the junction of two half-turns; the term "oblique" 
 
refers to sections in the intermediate region. Fig. 3 is of a normal organ of 
 Corti in radial section, Fig. 4 is of a nornixil organ in oblique section, and Fig. 12 
 is of a normal organ in tangential section. The ohlif|ue and tangential sections 
 are favorable for the observing of certain of the lesions because several of 
 each element of the organ of Corti are included in each section. The first 
 part of the first half-turn which deviates from the axis of the cochlear s])iral 
 and is almost parallel to the modiolus for a distance in the vestibule, has been 
 listed separately in the records made; it is termed the "vestibular part"; Fig. 
 2 shows the relation of this part of the ductus cochlearis to the rest of the 
 labyrinth. The fenestra rotunda is "beneath" the last portion of the vestib- 
 ular part. 
 
 Figs. 3 to 14, inclusive, are at the same magnification- — 295 diameters; they 
 are therefore directly comparable, and are at a magnification sufficient to permit 
 ready recognition of parts. The normal sections are inserted for comparison 
 with the injured ones. 
 
 The loss of single or of a few adjacent outer hair cells is the definite injury 
 of most frequent occurrence and is evidently the least severe of the definite 
 lesions. Figs. 6, 7, 8, and 13 show sections having such lesions in radial, 
 oblique, and tangential sections. Special features in the various sections are 
 mentioned in the legends (q.v.). Such loss of hair cells is usually associated 
 with a displacement of the corresponding Deiters' cells, frequently showing as 
 a nuclear displacement, as in Fig. 7. Derangements of Deiters' cells without 
 loss of hair cells have not been called injuries in the records made for the reason 
 that they may possibly be artefacts. For some time I w'as not certain that the 
 absence of isolated hair cells indicated an injury, but after finding such gaps 
 in many of the best preserved cochlese I have arrived at the conclusion that 
 these are not artefacts. This belief is further strengthened by the increasing 
 frequency of such absences as an area of more severe injury is approached 
 in following the organ of Corti in serial sections. As may be seen in the illustra- 
 tions given it is possible to have several degrees of severity of such injuries, 
 depending on the proportion of outer hair cells which are missing. It ranges 
 from the loss of a single cell in one section with all the other sections of the 
 region normal, up to the loss of the majority of the cells in all sections for a 
 considerable distance. All these various lesions I have grouped under the term 
 of first degree injury, which may be defined as the loss of part of the outer 
 hair cells with or without derangement of the Deiters' cells. 
 
 The absence of all the outer hair cells is the condition found next in order 
 of frequency to the preceding. Fig. 8 illustrates this lesion. This condition may 
 be present in all the sections of a half-turn or more; it ranges from this large 
 extent to a single section. Since only every fifth section has been saved, the 
 presence of this condition in a single section of a series means that it may have 
 extended over any or all of the four sections to either side which were not saved. 
 It will be noted in the illustration that the organ of Corti retains its general 
 outline; this is one of the differentiating points between this injury and the 
 more severe types. This condition, absence of all outer hair cells with retention 
 
of the general shape of the organ of Corti, lias been termed second degree injury, 
 for purposes of reference. 
 
 Of less frequent occurrence than the preceding condition is that illustrated 
 in Fig. 9. Not only are the outer hair cells missing but also the organ of Corti 
 is crushed out of shape; the illustration shows the usual condition of the tilling 
 of the tunnncl, Xuel's space, and the outer tunnel space with cellular debris. 
 In some cases there is more or less vacuolization of the mass. It will be observed 
 that the inner hair cell is present, as it is in the other lesions so far described. 
 This condition does not, in my material, occur in isolated sections, but areas so 
 injured are always adjacent at one end, and usually at both, to areas of lesser 
 or of greater injury. This condition, absence of outer hair cells associated 
 with a general crushing of the organ of Corti with massed or vacuolizcd debris 
 in the large spaces of the organ, has been termed third degree injury. 
 
 A more severe lesion of the organ of Corti is that illustrated in Figs. 10 
 and 14. In this lesion the outer hair cells are all absent, the organ of Corti 
 is badly broken up, the cellular debris is usually vacuolized but may be massed 
 as in the typical third degree injur}-, and the inner hair cell is absent. The 
 cells of the internal spiral sulcus are frequently vacuolized. This condition 
 has been termed fourth degree injury, and is characterized by the severe dis- 
 integration of the organ of Corti with absence of the inner hair cell, which 
 is, of the special sensory epithelial cells, the least often missing. In only one 
 instance was the inner hair cell observed in an abnormal condition when the 
 rest of the organ of Corti in that section was normal. Two adjacent sections 
 of a series (every fifth section saved) show a chromatolysis of the inner hair 
 cell. In one of these two sections there is no other injury evident; the other 
 section has part of the outer hair cells missing. Elsewhere definite lesions of 
 the inner hair cells have been obsen^ed only in association with severe injuries 
 to the rest of the organ of Corti. This fourth degree injur)-, like the third de- 
 gree, is not found in isolated sections in otherwise normal areas, but areas of 
 it are bounded by areas of lesser degree of injury. 
 
 Fit,'. 1 1 sh(nvs the most complete destruction of the organ of Corti which 
 is present in my material; it occurred in a zone of fourth degree iniury, 
 and since it occurred but once I have not given it a special designation of degree. 
 
 The distribution of the lesions of the organ of Corti in the various cochlene 
 studied is shown in the charts of Plate IV. In making these charts the relative 
 lengths of the various, half-turns have lieen approximated, instead of show- 
 ing each half-turn as of the same value. To indicate the various degrees of 
 injur}- three shades of grey, parallel lines, and dots have been used. The 
 darkest shade of grey represents the condition that has been termed fourth 
 degree injur}-; the intermediate grey, third degree injury; and the light grev. 
 second degree injury. The narrowest of these light grey zones represent single 
 sections, though they are proportionately t<M) wide for the actual ratio which 
 a single section ^^hnuld cover in tlic chart. The parallel lines indicate areas 
 where all sections are in the condition termed first degree injury; and the 
 dots indicate first degree injury in isolated sections. Where two or three 
 
adjacent sections are in this condition it has been shown by drawing a Hne 
 underneath the dots, unless it is between zones of more severe injury, in which 
 case parallel lines have been used. The number of dots is not, in most cases, 
 the exact number of sections with lesions but the number of dots indicates the 
 relative frequency of sections showing injury to the organ of Corti. Since 
 only every fifth section has been saved, the absolute distribution can not be de- 
 termined from these series. The position of the ends of the injured areas 
 can be determined only by means of graphic reconstruction which allows for 
 the difference in length of the part of the organ of Corti contained in radial, 
 oblique, and tangential sections. I have devised a suitable method for making 
 such graphic reconstructions, but have not used it here since most of its value 
 over the method of approximation would be lost due to having only every fifth 
 section. In studying the cochlese the organ of Corti and other structures were 
 followed section by section from the vestibular end of the cochlear duct to 
 the apical end, being traced back and forth through each series for the dif- 
 ferent turns. The notes, from which the charts presented were made, were 
 jotted down at the time of observing injured areas during these examinations 
 of series. 
 
 For convenience of reference, the conditions recorded have been grouped 
 in four charts. 
 
 In Chart I are placed all cases wdiere the outer ear was entirely open and 
 the detonation used was one shot from a 45 caliber Colt automatic pistol with 
 the muzzle at 15 cm. from the ear. Most of these are the open ears of animals 
 in which the other ear was "protected;" in all cases the 15 cm. was measured 
 from the opposite ear, and the barrel pointed downwards about 20 degrees 
 along the left side from above and in front. 
 
 In Chart II are presented the controls with the open rubber ear and glass 
 tubes of various sizes. From a study of the great variations in individual 
 cases in the cochleae recorded in Chart I, where all were exposed to as similar 
 traumatic conditions as possible, it is evident that the number of controls with 
 each tube is too small, there being only one with each, except with the 2 mm. 
 tube, and in this case the extra two animals were used because wax entered the 
 end of the tube during the experiment (cf. middle ear observations). 
 
 In Chart III are presented the conditions of the cochleae of the "protected" 
 ears. To facilitate comparison, these have been arranged in the same order as 
 the middle ear observations on the protected ears (q.v.). 
 
 In Chart IV are presented the conditions of the cochleae of animals sub- 
 mitted to detonations other than the usual one shot at 15 cm. 
 
 Besides these, two animals were taken as controls of the possible injury 
 to the ears while in the basket during the experiment with others. One of 
 these, animal 62, was also placed in ihe holding apparatus as a control of pos- 
 sible injuries by this procedure. The other, animal 63, simply remained in 
 the basket during six experiments, being exposed thus to the sound of six shots 
 from the pistol at a distance of about 25 feet, the gun pointing away from the 
 
basket. Both cochleie of animal 62 are entirely normal. The left cochlea 
 of animal 63 has a few sections with missing or distorted outer hair cells in 
 the sixth half-turn; the right cochlea has ab<nit 30 isolated sections with some 
 outer hair cells missing, scattered throughout its length except in the vestibular 
 part and the eighth half-turn; the injured sections are most numerous in the 
 third to the sixth half-turns. 
 
 Shrinkage and chromatolysis of i)art of the cells in parts of the si)iral 
 ganglion are present in many of the cochleae; this condition is present most 
 often in the vestibular part and lir.^t half-turn; less frequently it is present 
 in the second, third and fourth half-turns, and occurs very seldom alx)ve this 
 level. In general the distribution corresponds with the injuries to the organ 
 of Corti. but there are many exceptions to this general arrangement. In the 
 vestibular part and first half -turn shrujiken ganglion cells are much more fre- 
 quently j)rescnt in the cochleae of unprotected ears than the protected ones in 
 which definite lesions of the organ of Corti occurred; and in these unpro- 
 tected ears the number of shrunken ganglion cells frequently appears to be a 
 much greater proportion of all the cells than the proportion of hair cells miss- 
 ing in the corresi)onding region. On the other hand, in many cases the ganglion 
 cells show no injury in regions corresponding to parts of the organ of Corti 
 that were severely injured. The possibility must always be kept in mind that 
 these ganglion cell alterations may be artefacts; but after observing many cases 
 where the occurrence of a zone of injury corresponds to a zone of ganglion 
 cell shrinkage and protoplasmic change I am of the oj)inion that these in- 
 dicate a true lesion. Animals allowed to live a longer period of time after 
 being submitted to detonations are needed to definitely settle this point. In 
 two cases all the ganglion cells were in bad condition, but in both of these 
 the general fixation w-as so poor that the alteration is in all probability an arte- 
 fact. In a few cases some of the nerve fibers leading from the ganglitw to the 
 organ of Corti are definitely degenerating; in most cases they appear nearly, 
 if not entirely, normal. The fibers in the organ of Corti itself can not be 
 seen in the sections of the more severe lesions. 
 
 A peculiar condition is present in the cochleae of animal 44. The ductus 
 cochlearis, sacculus, and utriculus are distended to an unusual size. Reissner's 
 membrane is bulged into the scala vestibuli and is longer than normal. It is 
 not thickened. The walls of the utriculus and sacculus are similarly dis- 
 tended. The distention is somewhat less in the right cochlea. The right 
 cochlea of animal 37 has a similar, but much less distended, condition from 
 the basal end to the fifth half-turn, and the second and third half-turns of 
 animal 27 show it in slight degree. In the one wiiii the greatest distention, 
 the left cochlea of animal 44, the stria vascularis of most of the third half- 
 turn and of part of the first half -turn has a peculiar enlargement of the blood 
 vessels. The enlargement of the blood vessels of the stria vascularis and the 
 distention of the endolymphatic channels of the left cochlea of animal 44 may 
 
 8 
 
be associated as cause and effect but it seems doubtful in view of the facts 
 that enlarged vessels are not present in the other cases of distention and that 
 several cases of enlarged vessels, though of much less extent, are present in 
 cochlcc-e where no distention has occurred. I wish to specifically state that I 
 am undecided whether either the enlargement of the vessels of the stria vas- 
 cularis or the distention of the endolymphatic channels has been caused by the 
 detonations. 
 
 DISCUSSION OF RESULTS 
 
 In discussing the above observations upon the labyrinths their bearing 
 upon the relative efficiency of the various protective measures will be con- 
 sidered first and the evidence from the three sets of observations which I 
 have made correlated. Then a comparison will be made of the lesions in my 
 material with those recorded by other observers upon detonation injuries of 
 the labyrinth, and the bearing of the results upon the general problem of the 
 physiology of hearing indicated. 
 
 I. Relative Efficiency of Protective Measures. — The condition of the mid- 
 dle ear parts and the tambour results, reported previously, both indicated a di- 
 vision of the protective m.easures into two distinct groups on the basis of 
 their relative efficiency in preventing the passage of the force of the detonation 
 waves used; these two sets of results agree in the devices which would be placed 
 in each group. Drv^ cotton, the Elliott protector, and the Wilson-Michelson 
 instruments are in the less efficient group. Examination of Chart III shows 
 that the division into groups on the basis of the cochlear results is not so 
 well marked; each of the protective measures failed to prevent definite coch- 
 lear lesions in one or more of the ears with which it was used. Even here, 
 however, a ranking of the devices is evident; and two of the three protective 
 measures Avhich are in the less efficient group on the basis of the other tests 
 again rank lowest. 
 
 It may be that one of the groups of observations is of more value than the 
 others ; if so, this should receive the most consideration in drawing conclusions. 
 I would call attention to the fact that the animal experiments are the ones 
 Avhich indicate the devices that permit an injurious amount of detonation waves 
 to pass; the physical experiments are of value in helping to place the preven- 
 tives in their relative order of efficiency. The tambour method, on the other 
 band, has the advantage which all experiments in physics have over biologic 
 work; i. e., the materials used are not subject to the individual variations which 
 the reactions of living organisms are. It is evident from the great variations 
 in the cochlear injury in the cases where the ear was open and the conditions 
 were as similar as possible that there is either a great individual difference in 
 guinea pigs in the degree of susceptibility to injury of this type or an entirely 
 unrecognized factor acting to modify the detonations (see Chart I). In the 
 conduction of the animal experiments with protective measures there are oppor- 
 tunities for errors in technic ; they were recognized and guarded against, but 
 the possibilitv must be kept in mind that in some cases the wax packing used 
 may not have completely prevented the entry of injurious force through the 
 
crevices around the tube which it was supposed to close, or that the device 
 may not have been properly jilaccd in the rubber ear. The foniier error 
 is the more probable ; the latter is one that is more likely to occur in the 
 use of devices by troops than under laboratory conditions. If it were not for 
 the great individual diflferences in the long series of controls (Chart I), I 
 would be inclined to think that the possible errors mentioned alx)ve had oc- 
 curred often, and that therefore the cochlear results were almost worthless 
 as a basis for comparison of the relative efficiency of the devices. But, if 
 such were the case, the (|uestion immediately arises as to why the middle ears 
 were not also damaged in a like ratio. As a possible exi)lanation of the 
 discrepancy here might be advanced the general belief for many years among 
 otologists that in cases of air wave trauma of the ear the injury to the laby- 
 rinth is less when the tympanic membrane ruptures than when it remains 
 intact; the explanation advanced is that the force is expended in ru])turing 
 the tympanic membrane. The statements are based upon clinical experience. 
 Yoshii (1909) reported one animal which has a bearing upon the subject. In 
 this case a guinea pig was exposed to the detonation from the firing of a re- 
 volver at 20 cm. (size of gun and j^sition witli reference to the animal not 
 given). At autopsy it was found that the right middle ear was l)adly damaged 
 while the left middle ear was entirely normal. Study of the cochlere showed 
 the right one to be entirely normal, while the left one showed "very light de- 
 gree alteration." From his description the alteration is less than anything T 
 have called a definite lesion. This case agrees with the clinical view. In my 
 material, animals 17 and 18 were the only ones in which, under similar con- 
 ditions for the two ears, one tympanic membrane remained intact and the 
 other ruptured. In animal 17 the cochlea of tl>e side with the normal middle 
 ear was severely injured, while the other cochlea was only slightly injured. 
 In animal 18 difficulties in technic prevent any definite statement as to the 
 cochleae. Since the tympanic membrane was rui^ured in all cases of oj)en ears 
 exposed to the usual detonation, no comparison is jxissible in this series. How- 
 ever, there are many cases here, and in the controls with the open rubber ear 
 and glass tube, in which the cochlea was severely injured. Of the ears with 
 which dr>- cotton, the Elliott protector, and the Wilson-Michelson instrument 
 were used, all had damaged middle ear parts ; one of each group of three had 
 the tympanic membrane ruptured, though less severely than in most of the cases 
 of open ears. With dry cotton, the cochlea of the ear with a radial slit in the 
 tympanic membrane is definitely injured; the injury to this cochlea is greater 
 than to one of the other two, and less than the injury to the third one. \\ ith 
 the Elliott protector the cochlear injury is nnich less in the case with a rup- 
 tured tympanic membrane thati in the two where it remained intact. W ith 
 the \\ ilson-Michelson device the c(»chlear injur)' in the case of the ruptured 
 tympanic membrane is about the same as in one of the other two and less 
 than the injury- in the third ca^e. With the rest of my material such com- 
 parisons can not be properly made, because the force of the detonation waves 
 reaching the ears varied greatly, due either to different protectors or to dif- 
 
 10 
 
ferent distances used. While some of my cases are in accordance with the 
 idea that rupturing of the tympanic tends to protect the labyrinth, it seems to 
 me, on the whole, that the exceptions to the rule are too numerous to accept 
 it as an explanation of the inconsistency between the middle car and the coch- 
 lear conditions. In this my material agrees with the clinical experience of 
 Meyer with troops submitted to modern battlefield conditions. It seems im- 
 probable that a true "bone conduction" can have played much, if any, part 
 here, since the vibrations would have had to pass through a person's body to 
 reach the ground on which the anim.al rested. 
 
 The condition of the cochleae of animal 63, used as a control for pos- 
 sible injury while in the stock basket during the testing with other animals 
 (see page 7), was a surprise to me, as I fully expected this control to be 
 normal ; animal 62 had both cochlea entirely nonnal. There is a possibility 
 that the lesions present, outer hair cells missing in isolated sections, are not 
 due to detonations, in w^hich case all the lesions of this nature would have to 
 be ruled out of consideration. On the other hand, if they are due to the de- 
 tonations of the pistol at the distance at which the basket was placed, (25 
 feet with the gun pointing in the opposite direction), all the cases of such 
 "isolated section" lesions must be considered as possibly due to such an origm 
 and their bearing on the protection afforded by devices thrown out. At the 
 time of the experimentation I considered the distance sufficient to avoid any 
 such complication; at present I must leave the question of interpretation open. 
 Here, as in the other groups, variation has occurred; one animal normal and 
 one injured ( ?). 
 
 As the most suitable way of determining the ranking given by the com- 
 bined tests to the protective measures, the method of adding the rankings given 
 by the different tests has been chosen. All three sets of observations are given 
 the same value by this method. The devices tested only by the tambour method 
 are omitted in this tabulation. To determine the order of efficiency as given by 
 the tambour method the results with the three guns used are ranked. AMien 
 two devices are tied for a place, the sum of this and the next lower ranking 
 is halved and each of the devices given this number. (See Tables I and II.) 
 
 The ranking arrived at by this method is open to criticism, and is, at best, 
 only an approximation. The division into two groups is very definite, however; 
 and the other requirements for military use should be the deciding factor in 
 choosing from the more efficient group, rather than the slight differences in 
 the laboratory results with these protective measures. These other factors 
 have already been considered in the previous reports and need not be taken up 
 here. It suffices to state that the "Tommy" is the best of the mechanical 
 devices from the standpoint of general military requirements for field use by 
 troops, and since it has a slight advantage over the others in the laboratory 
 tests it is the protective measure which seems to be indicated for a large field 
 trial. On the other hand, the results of the laboratory tests seem to eliminate 
 the need of field trials by troops of dry cotton, the Elliott protector, and the 
 Wilson-Michelson device. 
 
 11 
 
II. Comparison with Previous Work on Detonation Injuries. — The extent 
 and distribution of the injuries to the organ of Corti in the animals I have used 
 are quite different from those reported by \\ ittmaack, Yoshii, and Prenant 
 and Castex, but are similar to some of Hoessli's and of Hoshino's cases. \\ ith 
 the exception of some of Hoessli's experiments all the animals used 1)v other 
 workers have been exposed to detonations with the ears entirely open. W'itt- 
 maack's statements are very indefinite regarding his detonation cases ; some 
 animals were negtitive, and no statement is made of the extent of the injured 
 area in the ones which were injured. The one figure which he presented of 
 a detonation injury is from the next to the highest turn (fifth and sixth half- 
 
 Taule I 
 Ranki.ng ok the Devices by tiik Ta.mbour Method 
 
 
 RANKING ACCORDING TO 
 
 SUMOE 
 RANKINGS 
 
 RESULTING 
 RANKING 
 
 PROTECTIVE MEASl'RE 
 
 22 
 CALIBER 
 
 38 
 
 CALIBER 
 
 44 
 
 CALIBER 
 
 Vaselined cotton 
 "Tommy" 
 Glycerined cotton 
 Mallock-.\rmstrong 
 Wax cone 
 Wilson-Michelson 
 Elliott Protector 
 Dry cotton 
 
 1/2 
 3 
 
 VA 
 
 4 
 5 
 8 
 6 
 
 7 
 
 1 
 
 4 
 
 2/2 
 5 
 6 
 
 7 
 8 
 
 2 
 1 
 3 
 
 5 
 4 
 6 
 7 
 8 
 
 4/2 
 6/2 
 8/. 
 
 ll'/2 
 
 14 
 20 
 20 
 23 
 
 1 
 2 
 3 
 
 4 
 5 
 6/2 
 
 8 
 
 Table II 
 Ranking of Devices by the Average oe the Three Sets of Results 
 
 
 RANKING ACCORDING TO 
 
 
 
 
 
 
 
 SUM OF 
 R.\NKINGS 
 
 RESULTING 
 RANKING 
 
 PROTECTIVE MEASURE 
 
 TAMBOUR 
 
 MIDDLE EAR 
 
 LABYRINTH 
 
 
 METHOD 
 
 CONDITIONS 
 
 CONDITIONS 
 
 
 
 "Tommy" 
 
 2 
 
 1 
 
 4 
 
 7 
 
 1 
 
 Mallock- .Armstrong 
 
 4 
 
 2 
 
 3 
 
 9 
 
 2/2 
 
 Glycerined cotton 
 
 3 
 
 5 
 
 1 
 
 9 
 
 2/2 
 
 Wax cone 
 
 5 
 
 3 
 
 2 
 
 10 
 
 4 
 
 Vaselined cotton 
 
 1 
 
 4 
 
 6 
 
 11 
 
 5 
 
 Elliott Protector 
 
 6^ 
 
 7 
 
 7 
 
 20'^ 
 
 6/2 
 
 Wilson-Michelson 
 
 6J4 
 
 6 
 
 8 
 
 20^ 
 
 tY2 
 
 Dry cotton 
 
 8 
 
 8 
 
 5 
 
 21 
 
 8 
 
 turns of my terminology) ; it resembles somewhat the lesion I have tcnned 
 third degree injury. A study of this and other figures given by Wittmaack 
 leads me to agree with the group of workers in Siebenmann's laboratory at 
 Basel ; 1. e., there are many artefacts due to faulty histologic tcchnic in the 
 work of Wittmaack, so that even his indefinite statements must bo discounted. 
 As in all of his work on cochlear injury by sound waves W ittmaack considered 
 the injury to the ganglion cells the primary lesion and the epithelial degenera- 
 tion secondary. The lesions found by Yoshii in the middle ears were very 
 similar to those of my unprotected animals. The two figures given by him 
 of the organ of Corti after exposure to single detonations show a condition 
 which agrees with that which I have termed fourth degree injury. (An ex- 
 
 12 
 
tensive quotation from Yoshii's description of the lesions observed by him was 
 given in the report on the Hterature, page 851 of the September, 1917, Journal 
 of Laboratory and Clinical Medicine, to which the reader is referred.) He 
 reported this severe lesion as present the whole length of the cochlea, which 
 is a lesion more extensive than is present in any of the animals I have used. 
 He also reported changes in the ganglion cells, and he, like the rest of the 
 Siebenmann group of workers, considered these to be secondary degenera- 
 tions and the epithelial primary. He also mentioned hemorrhage into the spaces 
 of the labyrinth in some cases. The size of the gun used by Yoshii was not 
 definitely stated; he merely said, "Diese Versuche wurden teils mit einer Kin- 
 derpistole und blossen Ziindhiitchen, teils mit Revolver und Patronen unmit- 
 telbar vor der Ohnnuschel und zwar jeweilen an beiden Ohren rasch nachein- 
 ander ausgeflihrt." He placed the muzzle of the gun much closer to the ear 
 than I did, and in reality exposed each ear to two detonations ; for my experi- 
 ments show that both ears are damaged at much greater distances than that 
 between the two ears of the guinea pig. This closer range may account for 
 the more extensive injury his animals received. He used eight animals in this 
 series; two were killed immediately, and one each after 2, 3, 8, 25, 45, and 
 60 days respectively. In view of my results it seems probable that more an- 
 imals might have given him more variation. In any case, his statements as 
 to some regeneration having occurred in the animals killed after the longer 
 intervals certainly needs confirmation with a greater number of animals for 
 each stage. 
 
 Hoessli, in his first series with detonations, was testing primarily air and 
 bone conduction, to determine which transmits the injurious force. He used 
 three guinea pigs with the incus removed on the left side of each, and two 
 animals with moistened cotton in both ears. All were placed in a cage and 
 a Swiss army revolver was fired five times at about 30 cm. above them. They 
 were killed 24 hours later. Each animal was reported by a separate proto- 
 col. In none of the cases was there any damage to the middle ear parts, 
 other than the operative injury in the animals with the incus removed. All 
 three of the cochleae in the cases with the incus removed were normal, as 
 were also three of the four ears which had moistened cotton in the external 
 meatus. In two of the three open ears with normal middle ear parts and 
 one of the cotton protected ears the cochleae had lesions in the organ of 
 Corti in the lower half of the second turn (third half-turn of my termi- 
 nolog}')- The injury as described agrees with what I have termed third degree 
 injury ; Hoessli noted that the inner hair cells were present, and stated that 
 there was no evidence of injury to the ganglion cells or nerve fibers, except 
 the fibers in the organ of Corti itself. Except for this half-turn he reported 
 the cochleae normal. Of the third case of open ear with normal conducting 
 apparatus, he said: ''Die Scala cochlcce ist im ganzen normal und zeigt keine 
 Veranderungen. Einzig an derjenigen Stelle, wo wir in Fall 22 die ausge- 
 dehnten Veranderung vorfinden, sehen wir hier einen teilweisen Mangel der 
 ausseren Haarzellen bei sonst normalen Cort. Organ. Die iibrigen Skalateile 
 
 13 
 
sind chcnfalls normal." Apparently this was a slij^lil injury; l^lfjcs^li was 
 properly very cautious as to the interpretation of possible artefacts. In those 
 of Hoessli's cases which are comparable to mine, cochlear injuries occurred 
 in the same region where mine show the most frequent injury; i.e., the third 
 half-tuni. The cf)ndition of the unprotected middle ear parts in his cases 
 shows that he was working with a less powerful wave than I have used, for 
 no injury to the middle ear parts occurred. Hoessli believed that the one case 
 where the wet cotton failed to protect was due to the scratching lof)se of the 
 cotton by the animal. He followed this series by one in which he used four 
 cats, the left ears stopjied with wet cotton, the right ears left open. To prevent 
 scratching out of the cotton the animals were lightly narcfrtized and five shots 
 were fire<l at 2^ cm. above the four of them. As before, the animals were killed 
 24 hours later. The left ears in all cases were normal. In three of the four 
 right ears there was an area in the upjier part of the basal turn (upper part 
 of second half-turn) extending through about 15 sections (thickness of sections 
 not stated) where a slight variation from normal was found; the variation 
 consisting of a depression of the organ of Corti in the region of the outer 
 hair cells. The fourth case was entirely normal. In view of the variations 
 in individual cases in the longer series I have used the two exceptions in Hoes- 
 sli's short series are interesting. 
 
 While Hoessli was interested primarily in the question whether air or 
 bone conduction transmits the injurious waves, he called attention to the bear- 
 ing of the results with wet cotton to the protection of soldiers. All that he 
 says of this phase of it is here quoted verbatim : "Hier denkt man unwill- 
 kurlich an die vielen Falle von Schusstrauma bei Soldaten, welche Watte in 
 den Ohren getragen haben .sollcn. \\ ir sehen eben hier, dass wenn der Wat- 
 tepfropf nicht ganz fest sitzt, und am Ende gar niclit angefeuchtet ist, der Schutz 
 des Ohres ganz illusorisch ist." 
 
 The region in which the majority of the lesions have occurred in my ma- 
 terial is in general the same as was injured by the various guns used by Hoshino 
 (1917).* He exposed guinea pigs to the detonations of a medium-sized re- 
 volver, a hunting gun, an army rifle, and a cannon. With the small arms l)lank 
 cartridges were used and in most cases the shooting was directly toward the 
 ear, at distances varying from "close up" to 100 cm.; two series were run 
 with each gun. in the first group of series one shot was fired toward each ear 
 of each animal, in the second group several shots each, the number varied from 
 5 to 350. The cannon was one used as a "time piece" and was loaded with 
 only about four pounds of powder; the animals were placed two meters in 
 front of the muzzle ; they were blown as much as twenty meters by the ex- 
 plosion. Two animals were exposed to one shot each and two to five shots 
 each. The animals of the various series were killed at intervals varying from 
 "immediately" to fifty days after exjxisure. The greater number of animals 
 were handled by an injection fixation, using Held's formal-bichromate-acetic 
 
 •It is to be rejfrcttcH th.it the observations of this Japanese otologist are recorded in a lanKuage 
 which rentiers them inaccessible to so many invcstiRators. I desire to here express my thanks to Dr. 1. 
 Wat.inabe. an assistant in this laboratory, for reading this article to me. 
 
 14 
 
mixture. The resulting injuries to the labyrinth were more severe and wide- 
 spread in the cases where many shots were fired than in those "once exposed" 
 (really twice since each ear was considered separately in counting the shots),- 
 but were in the same region of the cochlear canal for each gun, whether one 
 or many detonations were used. Hoshino reported that the region of most 
 severe injury varied for the different guns; it was knvcst for the cannon and 
 highest for the revolver. The regions for each were: (1) revolver, second 
 turn and lower part of third; (2) cannon, upper part of basal and lower part 
 of second turn; (3) army rifle, upper part of basal turn; and (4) hunting 
 gun, lower part of second turn. One monkey was used, it was exposed to one 
 detonation from the rifle held close to the ear. The injured area extended the 
 whole length of the cochlea in this case, but Hoshino thought the wide extent 
 possibly due to the short distance rather than to the different type of animal. 
 The injuries to the organ of Corti varied from minor atrophic changes to com- 
 plete destruction and replacement by a simple epithelium. Hoshino also 
 broke the tympanic membranes of six animals and introduced staphylococci 
 into the middle ears, waited until a suppurative otitis had developed, and then 
 exposed them to detonations from the small arms. He found in general the 
 same type and extent of injuiy due to detonation as in the animals with normal 
 middle ears similarly treated. He added this suppurative otitis evidence in 
 support of the view that impaired conducting apparatus does not protect the 
 labyrinth from detonation injuries. Hoshino reported lesions involving the 
 tectorial membrane, which was sometimes "frayed out" and sometimes almost 
 entirely missing. While the technic used on my material is not favorable for 
 the study of the tectorial membrane, because of the way it is shrunken and fre- 
 quently turned up even in normal cases, I have observed no evidence that it has 
 definite lesions due to detonations. \\'hile Hoshino stated that the area injured 
 was more extensive with repeated detonations than with one, he did not men- 
 tion variations in extent under identical conditions, such as my material shows. 
 The small amount of powder used in the cannon and the fact that no shell 
 was. used would indicate that the intensity of the detonation was not so great 
 as that of the majority of artillery pieces and exploding shells, but the plac- 
 ing of the animals in front of the muzzle where they were hurled twenty me- 
 ters by the explosion simulated to a degree the conditions in the battle field 
 where men are frequently hurled by the blast of an exploding shell and at the 
 same time exposed to the intense sound. It is of interest to note that the 
 lesions produced by Hoshino's cannon were of the same nature as those pro- 
 duced by the smaller detonations of both himself and others; this indicates 
 that the study of lesions due to relatively small detonations are of value in 
 interpreting the effects of more intense explosions. 
 
 Prenant and Castex (1916) placed animals in cages near large caliber 
 guns at Fontainel)leau. In no case was the tympanic membrane ruptured or 
 the middle ear inflamed ; ten guinea pigs and six rabbits were used. The 
 preservation of the labyrinths was poor; they reported extensive cochlear 
 Jesions of the type to l)c expected from previous work in this line with smaller 
 
 15 
 
guns. Since tliis is the only work in which animal ccKhlcie have been re- 
 l>(jrtcd after exposure to detonations of such large guns as they used, it is 
 very much to be regretted that the histoh)gic teclinic used gave such poor 
 resuhs, for this makes them of very httle vahie except for very indefinite 
 comparisons and conclusions. 
 
 The report of J. S. and John Fraser (1917), made upon autopsy ma- 
 terial from soldiers deafened by detonations, must be considered in the light 
 of the histologic tcchnic employed by them, which was such as to render the 
 results very indefinite, as they realized. Hemorrhage into the labyrinth and 
 about the entrance of the nerve roots in the fundus of the internal meatus 
 were definite findings of interest. It is almost imjKJSsible in their material 
 to differentiate the artefacts from the actual lesions in the organ of Corti and 
 nervous tissues. Wilson reported recently (Journal of the American Medical 
 Associatidn, August 24, 1918) the condition of a temporal bone secured at 
 autopsy six hours after the death of a soldier who had l>een deafened by a 
 shell explosion. (Wilson said that two were reported in the Harvey lecture 
 which he gave; but this is not yet available to me.) Formalin fixation was 
 used. He, like Fraser, reported hemorrhage in the base of the internal auditor}' 
 meatus. There was \cv\ evident damage to the cochlear parts ; edema and 
 small cell infiltration were mentioned as l)eing present in the ganglion, stria 
 vascularis, basilar membrane and organ of Corti. The epithelial cells and the 
 ganglion cells were "indistinct," doubtless due in part, at least, to the time after 
 death before placed in fixative and to the necessarily slow penetration of the 
 fixative, even though the superior semicircular canal was opened. 
 
 The presence in my material, except in the most severe injuries, and also 
 in Hoessli's detonation cases, of the inner hair cells is interesting in connec- 
 tion with Hoessli's observations on injurv' by the sound from organ pipes ; he 
 found the inner hair cells intact after the outer hair cells had disappeared and 
 even sometimes when the supporting apparatus of the outer hair cells had broken 
 down. These facts indicate either that the inner hair cells are more resistant 
 to injurious sound waves, or that they do not receive as great intensity of 
 the waves as do the outer hair cells. This is not taken into account in any 
 of the theories of hearing. The statement of Shambaugh (1911) that the ciliae 
 of the outer hair cells are in constant contact with the tectorial membrane 
 while those of the inner hair cells are free is suggestive in this connection. 
 
 None of the reports of previous experimental work involving detonation 
 injury of the cochlea make any mention of separated zonal lesions, which are 
 so plentiful in my material. (See, for example, "34 Rt." in Chart I.) It is 
 evident that if the variations in sound waves are perceived by any type of 
 perij)heral analysis, the occurrence of definite zones of injury to the organ of 
 Corti indicates that the parts injured were most active in converting the sound 
 waves into nervous energy. In other words, if either the Helmholtz theory 
 in its original form or in any of its modifications, or the Lehmann or the 
 Kwald or the Kohier theory, or the theories involving the tectorial membrane 
 as a differentiating mechanism, are correct, injured zones of the organ of Corti 
 
 16 
 
are to be interpreted as being in the areas of resonance for the sound waves 
 that caused the damage. If there is any definite pitch, or if there is a mixture 
 of vibration frequencies in the sound waves produced by the firing of a 45 
 caHber pistol, it seems reasonable to suppose that it will not vary with dif- 
 ferent shots to the extent that would cause the difference in cochlear lesions 
 observed under otherwise identical conditions; that is, open ears at the same 
 distance and direction from the gun. No attempt has been made to obtain 
 and analyze sound curves from the detonations used, so that no conclusions can 
 be reached along this line. 
 
 A general view* of Chart I, in which are presented the cochlear conditions 
 in the open ears exposed to the firing of one shot at 15 cm. from the muzzle 
 of a 45 caliber Colt automatic pistol, reveals that the average center of the 
 injured areas, other than isolated sections of first degree injury, is in the third 
 half-turn, except for the few cases with severe injury in the vestibular part 
 and first half-turn. The making of the charts with the relative lengths of the 
 half-turns indicated permits the ready recognition of the fact that the center 
 of the total length of the cochlear duct of the guinea pig is also in the third 
 half-turn. In Chart III, in which are presented the cochlear conditions in 
 the "protected" ears, the average center of the injured areas is somewhat higher; 
 and there is almost complete absence of injtuMes, even of the first degree in 
 isolated sections, in the whole of the basal turn (vestibular part and first and 
 second half -turns) of all the cochleae, except those in the Elliott and W'ilson- 
 Michehon series. 
 
 These observations of separated zones of injury and the average grouping 
 of the same are presented and attention called to them in the hope that they 
 may prove of value at some time, in connection with other data, in solution 
 of the problem of the physiolog}' of hearing. 
 
 It is a pleasure to express here my appreciation of the valuable sugges- 
 tions made by my chief. Dr. Huber, during the course of this work. 
 
 RESUME OF ALL MY REPORTS UPON WAR DEAFNESS AND ITS PREVENTION 
 
 1. Laboratory methods for the testing of measures for the prevention of 
 detonation injuries to the ear have been devised and such tests have been 
 carried out upon various protective measures. 
 
 2. These tests indicate that the measures tested may be divided into tvvO' 
 definite groups upon the basis of their efficiency in preventing the passage of 
 the force of the detonation waves used ; the variations within each group are 
 less decisive. In the more efficient group are the Scientific Ear Drum Pro- 
 tector "Tommy,"' the Mallock-Armstrong Ear Defender, cotton soaked with 
 glycerine, cotton soaked with vaseline, and the wax cone of the It:dian navy 
 type. In the less efficient group are dry cotton, the Elliott Perfect Ear Pro- 
 tector, and the Wilson-Michelson device. 
 
 3. The cochlear lesions produced by the detonations differ in extent and 
 distribution from those hitherto reported; the injur\' areas are frequently sep- 
 arated by normal zones; these lesions are recorded in a graphic form which 
 
 17 
 
makes them more available for reference Ihan if the usual method of written 
 I)rotoc(»ls had been followed. The facts are |ircsentcd without drawini:^ theo- 
 retical conclusions as to their bearing on tiie i)hysiolopy of hearing. 
 
 ItIIlUIOGK.\ril\ 
 
 (Only tlioM- artick-^ mciitinned in this rtjiort oi ;Ik muro^coiiR- (•Miinin.itKin of the 
 labyrinths arc hsted.) 
 
 Frascr, J. S.. and Frascr, John: The Morbid .Anatomy of War Injuries of the Ear, 
 
 Proc. Roy. Soc. Med., x, Otol. sect., 1917, 56-90. (This later appeared also in the 
 
 Jour. Laryngol., etc., Nov. and Dec, 1917 numbers.) 
 Hoessli, H.: Wciterc expcrimcntclle Studicn libcr die .Akustische Schadigung des Sauge- 
 
 ticrlabyrinths. Ztschr. f. Ohrenh.. 1917, Ixiv, 101-145. 
 Hoshino, T. : [.\ti Experimental Study of the Pathology of Ears Injured by Sound and 
 
 a Consideration of the Physioloijic Bearing of the Results], 1917. Kyoto Igaku Zassi, 
 
 xiv. (Xinety-seven pp. with 63 figures.) 
 Meyer: Das akustische Trauma, .\rch. t. Ohrenh., 1915, xcviii, 152-157. 
 Prcnant and Castex : Recherches expcrimentales et histologiques sur la commotion du 
 
 labyrinthe. 1916, Bull. .\cad. de Med., 3s., Ixxvi, 535-537. (A more detailed account 
 
 api)earcd later in the Paris Medicale, March 8, 1917.) 
 Shambaugh, G. E. : Das Verhaltnis zwischen Membrana tectoria und dem Cortischen 
 
 Organ. Ztschr. f. Ohrenh., 1911. Ixii, 235-240. 
 Wilson, J. G. : The Effects of High Explosives on the Ear, Jour. .\m. Med. .\ssn., Aug. 
 
 24. 1918. 
 Wittmaack, K. : t^ber Schadigung dcs Gehors durch Schalleinwirkning, Ztschr. f. Ohrenh., 
 
 1907. liv, 37-80. 
 Yoshii, U. : 1909. Experimcntelle Untersuchungen iiber die Schadigung des Gehorsorgan 
 
 durch Schalleinwirkung. 1909; ibid., Iviii, 201-251. 
 
 18 
 
Explanation of Figures 
 
 ABBREVIATIONS 
 
 a., Apical end of ductus cochlearis. 
 
 c.C, Cells of Claudius. 
 
 c.D.c, Cuticular processes of Deiters' cells (basal part). 
 
 c-H., Cells of Hensen. 
 
 ci.s., Cells of internal spiral sulcus. 
 
 f.r., Membrana tympani secundaria closing the fenestra rotunda. 
 
 g.sp; Ganglion spirale. 
 
 i.h.c, Inner hair cells. 
 
 x.p., Inner pillars. 
 
 I.O., Lamina spiralis ossea. 
 
 l.sp., Spiral ligament. 
 
 m.h., Basilar membrane. 
 
 m.rct., Membrana reticularis. 
 
 m.v., Membrana vestibularis (of ReissnerV 
 
 «., Nerve fibers in the spiial osseous lamina. 
 
 n.c. Cochlear nerve. 
 
 n.D.c, Nuclei of Deiters' cells. 
 
 n.o.p., Nuclei of the outer pillar cells. 
 
 N.S., Nuel's space. 
 
 o.h.c, Outer hair cells. 
 
 o.h.cA, Outer hair cells of the first row. 
 
 o-h.c.2, Outer hair cells of the second row. 
 
 o.h.c.3, Outer hair cells of the third row. 
 
 o.p., Outer pillars. 
 
 o.t.s.. Outer tunnel space. 
 
 ph.pr., Phalangeal processes of Deiters' cells. 
 
 sac, Sacculus. 
 
 s.t., Scala tympani. 
 
 S.V.. Scala vestibuli. 
 
 t.f., Tunnel nerve fibers. 
 
 t.s., Tunnel space of the organ of Corti. 
 
 utr., Utriculus. 
 
 v.p., "Vestibular part" of the ductus cochlearis. 
 
 v.sp., Vas spirale. 
 
 19 
 
Legends for Plate I 
 
 Fig. 1. — Outline drawing of a mid-modiolar section of a left cochlea of a guinea pig. 
 Guinea pig 55. left cochlea, slide 1, row 4, section 1, 15^. The arabic numerals in the 
 various sections of the ductus cochlearis indicate the designation of half -turns as used in 
 this article. The part in the modiolar section is considered as the center of each half-turn; 
 the junctions of the half-turns are in the sections which cut the curve of the organ of Corti 
 tangentially. 
 
 Fic. 2. — Outline drawing of a section of a right cochlea of a guinea pig to one side of 
 the modiolar axis, showing the position of what has been termed the "vestibular part" 
 of the ductus cochlearis and the relations of parts in "oblique" and "tangential" sections. 
 Arabic numerals as in Fig. 1. Guinea pig 21, right cochlea, slide 2, row 1, section 2, 15x. 
 
 Figs. 3 to 14, inclusive, were drawn with the aid of a camera lucida at a magnifica- 
 tion of 885 diameters, and have been reduced in reproduction to 295 diameters, one-third 
 of the original size of the drawing. Being at the same magnification, comparison is facil- 
 itated. Figs. 3, 4, and 12 are drawings of sections of the organ of Corti in normal condition, 
 and are presented for comparison with the ones having lesions. All the cochleae were 
 prepared by the same tcchnic and the sections used for illustrations were selected to 
 present the typical lesions observed. See the text matter for the technic and the terminology 
 used in designating the lesions. 
 
 Fig. 3. — Drawing of a normal organ of Corti in radial section. Guinea pig 21, right 
 cochlea, slide 1, row 4, section 8, second half-turn, 295x. As is well known, the shape of the 
 organ of Corti varies in the diflferent parts of the ductus cochlearis; allowance must 
 be made for this in comparing this drawing with those of lesions in other parts of the cochlea. 
 
 Fig. 4. — Drawing of a normal organ of Corti in oblique section. Guinea pig 41. right 
 cochlea, slide 1, row 5, section 2, second half-turn, 295'<. 
 
 20 
 
g.8p 
 
 in.b. 
 
 N^. ph.pr. 
 
 Plate I. 
 
 21 
 
Legends for Plate II 
 
 FiC. 5. — Organ of Corti, with first degree injury, radial section. Guinea pig 52, left 
 cochlea, 1-4-7. tliini li:ilf-turn, 2Q.S<. The outer liair cells of the second and third rows are 
 missing. 
 
 Fig. 6. — Organ of Corti, with first degree injury, radial section. Guinea pig 30. left 
 cochlea, 1-6-2, first half-turn, 295x. The outer hair cell of the first row is absent, and the 
 nucleus of the corresponding Deiters' cell is displaced downwards. 
 
 Fig. 7. — Organ of Corti, with first degree injury, oblique section. Guinea pig 47, 
 right cochlea, 1-5-5, second half-turn, 295x. Compare with Fig. 4. Some of the cells of 
 each row of outer hair cells arc missing. 
 
 Fig. 8. — Organ of Corti, with second degree injury, radial section. Guinea pig 40, 
 left cochlea, 1-3-2, fourth half-turn, 295x. All the outer hair cells are missing and the 
 Deiters' cells are partially destroyed. Xote that the general shape of the organ is retained; 
 it is different from that of Fig. 3, but is the normal outline for this part of the cochlea. 
 
 Fic. 9. — Organ of Corti. with third degree injury, radial section. Guinea pig 29, left 
 cochlea, 1-3-6, fourth half-turn, 295^. The shape of the organ is lost, being crushed; there is 
 cellular debris in the spaces of the organ; the outer hair cells are missing; the reticular 
 membrane in this case is broken and pieces of it are seen scattered through the mass. 
 
 Fig. 10. — Organ of Corti, with fourth degree injury, radial section. Guinea pig 28, 
 left cochlea, 1-4-2, third half-turn, 295>^. The severity of this type of lesion may be seen 
 at a glance; all the essential parts of the organ of Corti have been destroyed. Adhering 
 to the scala tympani surface of the basilar membrane may be seen two red blood cells and 
 one leucocyte ; this is one of the few cases where even this much hemorrhage was observed. 
 
 Fig. 11 — Drawing of a section in which the organ of Corti has been almost entirely 
 replaced in 48 hours by a simple epithelium. Guinea pig 50, left cochlea, 1-4-9, third half- 
 turn, 295*^. This is the only instance in my material in which the destruction is so complete. 
 I have not given it a designation of degree as was done with the types of lesions which 
 occurred often. 
 
 ')■) 
 

 23 
 
Legends for Plate III 
 
 Figs. 12, 13. and 14 sliould be compared directly in order to interpret readily the lesions 
 shown in 13 and 14. .\11 three are drawings of sections which have been selected as being 
 of corresponding p.nrts of tlic various organs of Corti. The elements of the organ of Corti 
 have been labelled in Fig. 12 only; reference should be made to it in studying Figs. 13 and 14. 
 Oblique and tangential sections are favorable for observing lesions because of the number of 
 each element present in a single section. 
 
 Fig. 12. — Normal organ of Corti in tangential section; the plane of section is parallel 
 to the modiolar exis. Guinea pig 33, left cochlea, 1-5-6, junction of fourth and fifth half- 
 turns, 295 ■<. 
 
 Fig. 13. — Organ of Corti with first degree injury, tangential section. Guinea pig 27, left 
 cochlea, 1-5-2. junction of fourth and fifth half-turns, 295x. When compared with Figs. 5 
 and 6, which are of radial sections of the organ of Corti, the nature of this lesion is better 
 understood ; a few or even single outer hair cells are missing in a place, ijuch lesions are 
 not artefacts due to the dropping out of bits of the tissue during or after the sectioning, 
 since the pieces are embedded in celloidin and there is no evidence of such vacancies in the 
 celloidin, which is itself faintly stained and would therefore show gaps. 
 
 Fig. 14. — Organ of Corti, with fourth degree injury, tangential section. Guinea pig 
 28, left cochlea. 1-2-7, junction of third and fourth half-turns 295x. Compare with Fig. 10, 
 which is of this type of lesion in radial section. Comparison with Fig. 12 emphasizes how 
 much destruction has occurred. 
 
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 {Sec I^Ojfcs JO and J7.) 
 
 For the explanation of the general plan of the charts and of the s>'mbols used, see 
 the text matter, page 7, and the preceding description of legions. The numhers in pa- 
 rentheses refer to the notes given in the legends for the individual charts. 
 
 Chart I. — A grapliic presentation of the condition of the organ of Corti in the 
 cochlea? of ears which were entirely open when exposed to the detonation produced by one 
 shot from a 45 caliber Colt automatic pistol, fired with the muzzle at 15 cm., measured from 
 the opposite ear, the barrel pointing downward about 20 degrees from the horizontal from 
 above and in front of the animal along the left side. 
 
 Chart il. — .\ graphic presentation of the condition of the organ of Corti in the cochleae 
 of the ears which had the open rubber ear and a glass tube, of the dimensions given in the 
 chart for each case, placed in the usual way. With the 2.0 mm. tube, examination of the 
 wax packing after the shooting showed the presence of wax in the end of the tube with' 
 animals 47 and 42. (Cf. Table II of the middle ear report.) 
 
 Chart III. — .\ graphic presentation of the condition of the organ of Corti in the 
 cochleae of the ears which were protected by the methods indicated. These are left cochleae 
 in every case, and the position of the gun was tiiat given in the legend for Chart 1, except 
 that the distance was measured from the protected ear. 
 
 (1) (Animal 56) The fixation of these turns is too poor for one to be certain as to 
 possible injuries of limited extent, there are none of large extent. 
 
 (2) (Animal 53) The fixation is so poor that the sections arc worthless for the 
 determination of detonation injuries. 
 
 (3) (.Animal 30) The apex of this cochlea was accidentally crushed during its 
 removal; the resulting gross distortion is too great for one to be certain of the condition 
 of the organ of Corti in these apical turns. 
 
 Chart IV. — A graphic presentation of the condition of the organ of Corti in the 
 cochlejE of ears which were entirely open when exposed to detonations from a 45 caliber 
 Colt automatic pistol with other than the usual arrangement (see legend to Chart I). 
 The distance from the muzzle and the number of shots fired are indicated in the chart for 
 each case. For the more exact position of the gun eacii time, reference may be made to 
 Table 1 of the middle ear report. 
 
 (1) (.Animal 18, right cochlea) The fixTition is too poor for one to be certain of more 
 than the general condition; tlierc may be other areas of injury of small extent, but there 
 are no other extensive injured zones. 
 
 (2) (.Animal 18, left cochlea) This cochlea was not entirely sectioned because of 
 poor decalcification; the areas blocked ofT are those not sectioned; their condition is 
 accordingly iiiikiiouii. 
 
 I'l'BLiSMKK s .XiiTi. Tlie cxact distribution of the fourth degree injury <loes not show 
 clearly in these charts as printed, owing to the lack of differentiation of the intermediate 
 and dark grays. 
 
 28 
 
1 
 
 Gaylord liros. 
 
 Makers 
 
 Syracuse, N. Y 
 
 PAT. JAN, 21,1908 
 
 
 392638 '^'PZ5o 
 
 
 UNIVERSITY OF CALIFORNIA LIBRARY