'Xi-nv'ti^Lv^/^^.^K^'C^ J. M. RUSK, c/ecle/ai^ o/ (S^ai€'ciim/ie. LIBRARY OF CONGRESS. PRESENTED BY UNITED STATES OF AMERICA. \ U. S. DEPARTMENT OF AGRICULTURE. HOG CHOLERA: ITS HISTORY, NATURE, AND TREATMENT, AS DETKimiXED BY THE INQUIRIES AND INVESTIGATIONS THE BUREAU OF ANIMAL INDUSTRY. WASHINGTON: GOVERNMENT PRINTING OFFICE, 1889. 15612 H 0—1 ^^-^i^ ^ r^ O <\n3 ;v^ \. TABLE OF CONTENTS. Pago. Introduction and Spread of Hog Cholera in the United States 9 Investigation of Swine Diseases 14 Sympto:\is and Post-mortem Appearances in Hog Cholera :5:> '^.vsions produced hy hog cholera 34 (a) Acute type :U (b) Chronic forms 3r> Hlstory and Autopsy Notes of ax Outbreak of Hog Cholera 37 Disease in Healthy Pigs Caused by Material from this Epizootic... 50 Brief Summary op tiii^ Important Features of this Epizootic 52 Heramorrliagic lesions 52 Ulcerative lesions 53 Complications 54 Lung lesions 54 Bacteriological Observations 58 The Causation or Etiology of Hog Cholera 03 The bacillns of hog cholera 03 Staining of hog-cholera bacteria 05 Biologj" of the hog-cholera bacillus 06 ((() Diagnostic characters 66 (b) Other physiological characters 69 The Diagnosis os- Hug Cholera by Means of Inoculation 63 Vitality of Hog-Cholera Bacilli and their Resistance to various Destructive Agexts 75 Resistance of hog-cholera bacteria to heat in liquid media 75 Vitality of hog-cholera bacteria in otdinary water 75 Resistance to continuous drying at ordinary temperatures 78 Some E.yperimknts on thk length of time during which Hog Chol- era Virus re.mains alive in the soil 80 A few Additional Observations as to the A^itality of Hog Cholera Virus in the soil at the Experiment Station 8G The Effect of Some Disinfectants on the Virus of Hog Cholera... 87 Mercuric chloride , 88 Carbolic acid 88 Iodine water 89 Permanganate of potash 89 Mercuric iodide 89 Snlphate of copper 90 Hydrochloric acid 90 Chloride of zinc 90 Sulphuric acid 90 Crude carbolic acid 91 3 Page. Ordinary Lime as a Disixfectaxt fou Hog Cholera 93 Disinfection of the soil with lime 99 Is THERE ANV RESISTANT SpORE STATE IN THE LiFE HiSTOUY OF THE BA- CILLUS OF Hog Cholera 101 Ways in which Swine become Infected 105 By way of the digestive tract 105 a. Fcediug diseased viscera 105 1). Feeding pure culture of Hog Cholera bacilli 107 Subcutaneous inoculation 109 lutra-veuous iuoculatiou r Ill Infection by way of the lungs 112 Some Observations on the Pathological Action of Hog Cholera Bac- teria 113 Bacteriological Investigations of Hog Cholera in Nebraska, Illi- nois, and Maryland IIC Differential Characters of the Hog Cholera Bacillus 119 Bacillus from Nebraska 119 Bacillus from Illinois.. 119 Bacillus from Maryland 120 REL.4.TION of Hog CiJOLERA TO THE PUBLIC HEALTH 120 Prevention of Hog Cholera 123 Isolation, Disinfection, and Cleanliness as Prevextive Measures — 123 Treatment of Hog Cholera 135 experi.ments on the prevention of hog cliolera by inoculation 139 I. Iuoculatiou of small doses of strong virus in the form of liquid culture.. 139 II. The effect of feeding small quautities of cultures on inununity 151 III. Injection of sterilized culture liquid to produce immunity 154 Tests with sterilized cultures on pigeons 155 Tests with sterilized cultures on pigs 159 Experiments on the Attenuation of the IIog Cholera Bacilli by Heat 167 Hog Cholera or Diseases closely Allied to it in other Countries .. 173 In Great Britain - 173 In Sweden and Denmark li^l In France 1>^C ILLUSTRATIONS, Page. Invkstigation of Hog Choleka: Plates I, II, III, aud IV. Illustrating necrosis and ulceration of the mu- cosa of the large iutestine, more particularly the cajcum 194 V. Showing ulcers in the ileum 194 VI. Showing hemorrhagic kidney 194 VII. Showing hemorrhagic lung 194 VIII. Showing hemorrhagic heart 194 IX. Collapse and hroncho-pneumonia 194 X. Microscopic characters of hog cholera bacilli 194 XI. XII. Growth of hog cholera bacilli in various culture media.. 194 XIII. Spleen aud liver of rabbit inoculated with hog cholera ba- cilli 191 XIV, XV, XVI. Photomicrographs of hog cholera bacilli, showing variation due to growth in ditfereut media 194 5 LETTER OF TRANSMITTAL. Washington, D. C, January 18, 1889. Sir : I have the honor to submit herewith a report upon the history nature, and treatment of the disease known in the United States as hog cholera. Our linowledge of this pest has been developed almost entirely by the inquiries and experimental investigations of the Bureau of Animal Industry; and while much of the information contained in this volume has been published in the reports of the Department of Agriculture, a systematic and complete statement of the facts has never before been made in a connected manner. It has been discovered in the course of these investigations that there are two very different and distinct epizootic diseases of swine in this country which are widely prevalent, and which had previously been spokeu of under the one name of hog cholera or swine plague. Tliese two names had, therefore, been used synonymously i)revious to 1886, when the differences between the diseases were pointed out in there- ports of this Bureau. It was then deemed best to apply the term hog cholera to that disease in which the intestines were found most af- fected, and in which the symptoms would come nearest to justifying the appellation. The other malady appeared identical, not only in symptoms and lesions but in the microbe which caused it, with the disease recently described in Germany by both Loffler and Schiltz un- der the name of Schweineseuche, or swine plague. For this reason it was considered best to call this affection swine plague in the reports, and thus preserve uniformity and prevent confusion of ideas in refer- ence to the diseases of swine in different countries. This volume treats exclusively of hog cholera, as it is the malady which has been longest under investigation ; but the material is on hand for an almost equally complete volume on swine plague, which we hope soon to submit for j)ublication. There are, of course, aiany other dis- eases of swine, some of wdiich are communicable in a certain degree, but none of which are so widespread and fatal as the two that have been named. Some of these, especiall3' the parasitic ones, are receiving at- tention, and may in the future be treated at length in the bulletins of this Bureau. The greater part of the detailed study of the disease, the planning of exx:)eriments, and the bActeriologic^l investigations have been carried 7 8 out by Dr. Theobald Smith, while the couducting of the experimeuts, the care of the experimental animals, and the general management of the experiment station have been under the direction of Dr. F. L. Kilborne. I can only speak in the highest terms of the untiring in- dustry and skill displayed by both of these gentlemen. The experiments in regard to prevention and medical treatment are being continued, but it is confidently believed that an understanding of the facts detailed in this volume will enable the owners of hogs to pre- vent or even arrest the great majority of outbreaks. It should be un- derstood, however, that the measures indicated must be enforced promptly, energeticallj', and thoroughly. D. E. SALMON, Chief of the Bureau of Animal Industry. Hon. Norman J. Colman, Commissioner of Agriculture. THE INTRODUCTION AND SPREAD OF HOG CHOLERA IN THE UNITED STATES. In the early days of bog-raising in the Uuited States these animals were comparatively free from disease, and wide-spread epizootic mala- dies among tliem appear to have been unknown. A circular letter of inquiry was recently sent from the Bureau of Animal Industry to the correspondents of the Department and to swine-breeders in all parts of the country, asking the date of the first appearance of hog cholera in the respondent's county, and a statement as to the health of swine pre- vious to that time. More than a thousand replies have been received, many of them so carefully written as to be of much interest and value. Nearly all agree in stating that at one time the swine industry was not subject to the ijeriodical losses from epizootics which now cause such discouraging losses. From the first appearance of this class of diseases the outbreaks became more numerous and more widespread until nearly all parts of the country are now subject to frequent invasions. The correspondence on this subject can only be briefly summarized in this bulletin. The first outbreak of disease supposed to be cholera that was referred to occurred in Ohio in 1833. It is reported from one county in South Carolina in 1837, and from one in Georgia as having existed in 1838. It existed in 1810 in one county in Alabama, one of Florida, one of Illinois, and one of Indiana. In 1813 it is reported from one county in [North Carolina. In 1811 one county in New York re- ports being affected. Its presence in 1815 is only mentioned by one correspondent from Kentucky. The thirteen years, from 1833 to 1815, inclusive, form a period in which but ten outbreaks of swine disease, supposed by the writers to have been hog cholera, were mentioned in these replies. It is evi- dent that during this period hogs were generally healthy throughout the country, and that the losses from disease were not sufficient to at- tract very much attention. The nature of the disease referred to as existing so long ago may, of course, be questioned at this day, and we have no means of deciding whether or not any particular outbreak was cholera or some non-contagious malady due to local conditions. It is reasonable to conclude, however, that the correspondents are correct in their opinion in most cases, because since 1815 the outbreaks mentioned became more numerous year by year until we fiud nearly the whole 9 10 country involved. This rapid increase of the number of affected sec- tions would seem to indicate that a contagious disease had been intro- duced and carried to wideh^ separated sections of the country, from which it extended until, with a year favorable to its propagation, we find a sudden and alarming increase. Turning again to the number of outbreaks reported, we find, in 1840, that there were two in Korth Carolina, one in Georgia, one in Illinois, one in Indiana, and one in Ohio. In 1847 four are given in Tennessee and one in Virginia. In 1848 we hear from it in one county in Illinois, two in Indiana, two in Kentucky, one in North Carolina, and one in Virginia. In 1849 it is mentioned as in one county in Indiana and in one county in Ohio. In 1850 we have accounts of three outbreaks in Georgia, one in Pennsylvania, one in Indiana, two in Kentuckj^, one in North Caro- lina one in Ohio, and two in Tennessee. In 1851 there were outbreaks in Illinois, Indiana, and Tennessee. In 1852 there were two reported in Illinois, two in Indiana, one in Missouri, and one in Ohio. In 1853 it invaded two new counties in Illinois, two in Indiana, two in Kentucky, one in North Carolina, four in Ohio, two in Tennessee, one in Texas, and one in Virginia. In 1854 it appeared in one more county in Illi- nois, four in Indiana, five in Kentucky, two in North Carolina, two in Ohio, and one in Tennessee. In 1855 it is found in six counties in Illi- nois, five in Indiana, one in Kansas, four in Kentucky, one in Missouri, two in Teimessee, and one in Virginia. The number of outbreaks mentioned by correspondents, it will be seen, is not less than ninety-three for the ten years from 184G to 1855 inclusive. As compared with the ten outbreaks reported for the pre- vious thirteen years this is an enormous increase. There can be little doubt that it was during the period from 1846 to 1855 that hog cholera became scattered over the country and fairly began that work of de- struction which has become so familiar to us in later years. Below will be found a tabulated statement of the replies from nearly eight hundred and fifty of our correspondents. The figures show the number of original hog -cholera infections reported for the different pe- riods from the first recorded appearance of the disease in this country to 1887. Of course there have been many counties infected within that time which are not referred to in these communications, but the large number that were mentioned gives as perfect an idea as can now be obtained of the development and spread of this contagion. It is to be remembered that the outbreaks mentioned are not secondary infections, but are the first outbreaks of the disease in the correspondent's local, ity, and in most cases the first which occurred in his county. In nearly all cases it is stated that previous to the outbreak referred to the health of hogs had always been good, and the losses from disease had been confined as a rule to a single animal at a time. 11 Xumber and dates of original infections wiUi hofj cholera and swine pUujue, as compiled from recent correspondence. States. 2 a H -* H s (-1 • (0 1 1 4 2 7 7 5 1 4 1 2 1 2 ? 1 1 3 1 1 3 13 26 3 1 1 1 1 1 4 8 5 11 5 3 4 17 12 1 Plorida 1 1 1 1 1 13 14 8 15 7 3 7 10 11 4 3 5 14 19 i;i 40 20 7 2 18 2 1 3 1 15 6 1 ? 1 1 1 2 1 3 2 3 1 ? 2 1 1 8 3 't 1 8 2 4 6 1 2 8 3 Iti 1 2 2 15 1 2 1 1 3 ? 2 1 •^ 2 1 1 1 1 1 9 7 4 10 3 4 Ohio 1 11 1 1 12 7 3 3 18 c 2 1 10 9 5 12 2 1 7 4 f) I 1 1 Texas 2 8 4 4 4 5 1 13 9 4 2 •2 1 5 2 3 4* 1 •1 1 "^ Whether the outbreak which occurred in Ohio in 1833 was the first introduction of hog cholera in this country or not, can not now be de- termined. It seems reasonably certain, however, that the contagion was imported from Europe with some of the animals that were brought from there to improve our breeds of swine. The investigations made in England and on the continent during the last year demonstrate that the swine fever of Great Britain is identical with our hog cholera, and that this disease is also widely scattered over the continent of Europe. This l)eiug the case, it would appear much more likel}' that the conta- gion was imported from there, as we know occurred with the contagion 12 of pleuro-pueumouia of cattle, than that it appeared spontaneously or was developed by tbe conditions of life in this country. Having been once introduced it spread gradually, following the lines of commerce and being for a long time confined to them, until, extejiding step by step, it has at one time or another invaded every section of the country in which swine raising is a prominent industry. Dr. George Sutton of Aurora, Ind., in 1858, wrote as follows: I have seen notices of this disease prevailing in the States of Illinois, Kentucky, Indiana, Ohio, New York, Massachusetts, Pennsylvania, and Maryland. It has pre- vailed extremely in Indiana, particularly in Dearborn, Ohio, Ripley, Rush, Decatur, Brown, Bartholomew, Shelby, Johnson, Morgan, Marion, Boone, Posey, and Sullivan Counties. It has also prevailed in Campbell, Kenton, Boone, Gallatin, Carroll, Breck- inridge, Bullitt, Bath, Henry, Henderson, Nicholas, Livingston, Union, and Crittenden Counties, Kentucky. It has also prevailed in Hamilton, Butler, Clinton, Fayette, and Clermont Counties, Ohio. Also in different portions of Illinois, and very severely in Wayne, White, and Gallatin Counties. It has also prevailed in the State of New York. The Ohio Farmer for January 3, 1857, quoting from the Buffalo Republic the extensive prevalence of the disease, says that "in western New York especially we learn it has been very fatal, but is now over. In conversation with one of the most extensive dealers in the neighborhood, a day or two since, he informs us that about six weeks ago he lost about four hundred in a very short space of time. A distiller in Jordan, during the month of September, lost fourteen hundred, which cost, in ad- dition, over $1,000 to have them buried. In Rochester, at all the i^rincipal points, and even among the farmers, the mortality has exceeded anything ever before heard of. A butcher in this city not long since purchased $500 worth of fat hogs, but they died so rapidly on his hands that he scarcely realized $75 on the investment." The Worcester (Mass.) Spy reports that many farmers in that city and vicinity are losing their swine by the mysterious and fatal disease known as the hog cholera. In the southeast part of the town it prevails in a greater or less extent upon nearly every farm. In most cases the disease is traced to Western hogs that have been sold by the drivers the present season, and which seem to have communicated the contagion to the other inmates of the sties in Vv'hich they have been kept. It is known that of many droves of Western shoats that have been sold at Brighton this season, and ped- dled about the State, nearly all have died. The disease has, no doubt, prevailed ex- tensively in other parts of the country, of which I have seen no notice. In this sec- tion of the country it has been extremely fatal. Over jiortions of Dearborn County it spread from farm to farm, and some of our farmers lost from 70 to 80 out of 100 of their hogs. At the distilleries the mortality has been very severe. I received infor- mation that more than 11,000 died at the distillery in New Richmond, in the summer and fall of 1856. The owners of the distillery at Aurora inform me that they have lost between C,000 and 7,000. A gentleman informs me that ho lost in 1856, at Ingra- ham's distillery, in Cincinnati, from the 1st of August up to the 24th of October, 1,285, losing 1,152 out of a lot of 2,408. Another gentleman informs me that at the distillery in Petersburgh, Ky., he lost from the 1st of Juno up to the 18th of October, 1856, 2,576. I have also received information from several other distilleries where the losses were large.* According to Dr. Sutton, this disease first appeared in Dearborn County, Ind., in July, 1850. * George Sutton, M. D., Observations on the supposed relations between epizootics and epidemics, and experimental researches to ascertain the nature of the recent epi- zootic among the swine, and the effects which diseased meat may have on human health. The North American Medico-Chirurgical Review, May, 1858, pp. 483-504. 13 Dr. E. M. Snow writes that — During the last five years this disease lias beeu seeu, from time to time, iu portioDS of the more eastern States, sometimes, as iu western New York iu 1856, proving quite severe and fatal iu comparatively limited localities. But in the Eastern States it has, to a great extent, originated Avith and has generally been coufiuedto hogs imported from the West. I think that iu no State east of Ohio has the disease prevailed ex- tensively, or attained the character of a wide-spread epidemic. In the vicinity of Providence, R. I., it has prevailed to some extent, more particu- larly among large herds of swiue during each of the last five winters, but has been mostly confined to hogs brought from the West, and has usually disappeared with the approach of warm weather. During the last winter it was more severe than iu any preceding, and was not confined to Western hogs. Neither did the disease, as here- tofore, cease with cold weather, but it continued until August, having destroyed more than 500 hogs in Providence and iu the adjoining towns during the first seven months of the present year, 1861. I havealso heard of its prevalence in various towns in Massachusetts during the same i)eriod.* The losses from hog cholera in the United States have been enormous. Estimates have from time to time been made from carefully-compiled data, and these have, so far as the writer is aware, never beeu less than $10,000,000, and have reached $25,000,000 annually. The inclusion of losses from other diseases is, however, unavoidable iu such estimates, and consequently some allowance must be made for these. The recent identificatiou of an epizootic pneumonia of hogs bj- the Bureau of Ani- mal Industry, a disease which appears to be identical with the kSchivelne- seuche of German writers, shows that the varieties of swine diseases in this country are more numerous than has beeu supt^osed. The erysipe- las of Europe (French, rouget ; German, Eothlaiif), and cliarbon have not yet been ideutifled as occurring in an epizootic or enzootic form among swiue in the United States but the existence of these diseases is not impossible, as the investigations have not yet been sufiQciently nu- merous to reveal the nature of all such outbreaks. The diagnosis of such diseases has been very uncertain in the past, because the symp- toms were not clearly defined, and not always sufiQciently characteristic. The most reliable means of discrimination between these maladies at present is the isolation of the microbes which produce them. The char- acteristics of these organisms are now so well knowu that the bacteri- ologist has no difficulty in distinguishing between them. * Edwin M. Snow, M. D., Hog Cholera. Annual Report U. S. Department of Agri- culture, 1861, p. 147. THE INVESTIGATIONS OF SWINE DISEASES. Among the first to investigate these diseases in the United States from a medical point of view was Dr. George Sutton, of Aurora, Dear- born County, Ind. In the extensive epizootics which prevailed in that county from 1850 to 1858 he had abundant material for study, and he noted the more salient features of the plague in a very clear and com- prehensive manner. While it is extremely difficult at this day to de- cide whether the outbreaks studied by Dr. Sutton were hog cholera or swiue-plagiie, or a combination of the two, his observations are very in- teresting and bring out many important facts. Of the syraptoniis, post mortem appearances, and nature of the mahidy, he says : This disease preseats a great variety of symxitoms. la January, 1856, wlieu tliis epizootic was at its height iu this section of country, I published a short notice of it in the Cincinnati Gazette. The symptoms which I then described I have found upon a more extensive observation to be correct. The hog first appears weak, his head droops, and sometimes iu a few hours after these symptoms diarrhea commences. There is frequently vomiting. In some cases the 'discharges were serous and clay- colored, sometimes dark, also bloody, and mucus resembling those of dysentery. The urine at first was generally small in quantity and high colored, but as the animal re- covered it became abundant and clear; this was one of the symptoms by which the men who were attending the hogs at the distillery ascertained that they were recover- iug. In a large number of cases the respiratory organs appeared to be principally af- fected ; there was coughing, wheezing, and difficult respiration. In some instances the animal lost the power of squealing, and the larynx was diseased. There was frequently swelling of the tongue and bleeding from the nose. In those cases where the respiratory organs were the principal seat of the disease there was generally no diarrhea or dysentery. In many instances the disease appeared to be principally con- fined to the skin ; sometimes the nose, the ear, or the side of the head were very much inflamed ; the ear swollen to twice its usual thickness. This inflammation would sjiread along the skin, sometimes over the eye, producing complete blindness. Sometimes one or more legs were inflamed and swollen, and the inflammation also extended along the body. The skin where w as inflamed was red and swollen. Some had large sores on their flanks or sides from 3 to 6 inches in diameter. Iu one instance, at the distillery, the inflammation extended along the fore leg, the foot became ulcerated and sloughed oft, and the animal recovered. Some appeared delirious, as if there was inflammation -of the brain. I examined the blood of four hogs which had this disease well marked; they were stuck, and the blood, arterial and venous, was caught in a bowl. It was cupped and presented a well- marked huffy coat. Death took place in from one to ten days after the attack. Sudden changes in the weather, particularly from warm to cold, appeared to increase the fatality of this disease. The average 14 15 ■ mortality of lioga that were iu pastures or fed ou slop was from 33 to 45 per cent., but it was frequently mucli more fatal if hogs were fed on corn — iu some instances ranging from seventy to eighty out of the hundred, and in some instances even higher. I found on opening the bodies of hogs that had died of this disease that they all presented evidences of a diffusive form of iullammation. From sixty-seven hogs that I have examined I found it was not confined to any particular tissue. Sometimes this inflammation was conlined to one organ; iu other cases it attacked several at the same time. The skin frequently presented jiatches of inllaumiation, and often had a purple appearance. In cutting through parts that were the most inflamed, the skin was swollen and the cellular tissue was infiltrated with serum. Frequently, however, the skin was merely discolored, without any swelling whatever. The stomach. was occasionally distended with food, and the mucous membrane in nearly every instance presented evidence of inflammation, sometimes extending over the whole stomach, at others only in patches. It was generally of a deeji-red color, thickened, and frequently softened. Sometimes it was covered with a viscid mucus.; in other instances there was an effusion of blood into the stomach. The mucous mem- brane of the snuill or large intestines, where there had been diarrhea or dysentery presented in all instances evidences of inflammation ; iu patches it was red, thick- ened, sometimes softened, and occasionally ulcerated ; where there had been dysen- tery there was generally bloody mucus found in the large intestines. The bladder generally contained urine ; sometimes its mucous membrane was inflamed, and iu one instance there was an efi'u^iou of Ijlood into this organ. In a large number of cases I found evidences of j)eritoneal inflammation, such as redness of this membrane, ef- fusion of turbid or bloody serum, adhesions between the intestines and between the intestines and sides of the body. In three instances blood was effused into the peri- toneal cavity — iu one instance more than a quart ; it appeared in this case to come from the liver. The liver was occasionally the seat of this inflammation, not only in its investing membrane, but the parenchyma ; sometimes there were abscesses, and in one instance portions of it were gangrenous. The lymphatic glands were gen- erally of a dark-red color, frequently resembling clots of blood. Tiiis disease of the lymphatic glands was of common occurrence. The lungs were frequently the seat of this inflammation, portions of one or both presenting difterent appearances, from simple congestion to complete hepatization ; sometimes there was ulceration, and frequently there was a turbid or sero-puruleut or bloody effusion into the i)leural cavity ; sometimes there were extensive adhesions between the lungs and pleura of the ribs. At first I was inclined to believe this malady to be a form of iileuro-pueumonia, but after I became better acquainted with it I found that the inflammation was not uniformly confined to any organ. In a number of instances the mucous membrane of the bronchia was deeply inflamed and the inflammation extended to the trachea and larynx. In several instances the larynx was inflamed, resembling laryngitis. One animal that had great dithculty in breath- ing and could make no noise I had knocked in the head, and on examination I found the mucous membrane of the larynx and epiglottis inflamed and swollen; also the tongue was swollen. There were evidences in several instances of pericarditis, which had produced adhesions between the heart and the pericardium. The brain, from the difficulty of opening the skull, Avas examined only iu one instance; it was found healthy, although I feel confident it was frequently the seat of the disease. From these examinations we sec ihafc it is a misnomer to call this malady cholera. It is a contagious inflammatory disease, the inflammation being confined to no par- ticular tissue, sometimes attacking only one, at others several, in the same animal. Evidences of this inflammation were found in the dermoid, the cellular, the serous, the mucous, and glandular tissues. I consider it a diffusive form of inflammation from the manner in which I have witnessed it spread along the skin. In one night I Jiave seen it extend from the eye to the ear— the ear becoming inflamed and swollen. 16 Altliougli we liave not been able to show that this is a cholera epizootic, still the facts elicited may be of interest and remove doubts at some future period. But, then, if this malady does not resemble cholera, does it resemble any of the diseases to which the human system is subject ? I think not. Like the specific eruptive diseases, it is highly contagious ; the infection has a period of incubation of from twelve to twenty- days, and one attack appears to exempt the animal from a second. But in this dis- ease, although petecchiic and an eruption may appear on the skin, its principal char- acteristic is a diffusive form of inflammation which may attack nearly every tissue and snread like an erysipelas. But then, again it differs from this disease, as it is well known that in erysipelas one attack does not exempt the system from a second ; and although erysipelas may be contagious, still it is doubtful whether the period before the eruption shows itself is so uniform as in this disease, and while erysipelas is gen- erally confined to tbe skin this inflammation most frequently attacks the lungs and mucous membrane of the alimentary canal. This disease appears to be intermediate between the specific eruptive diseases and erysipelas, partaking of the nature of each, and probablj'^ not having its exact resemblance among the diseases to which the human system is subject.* Of his experiments ami observatious ou the contagioustiess of the disease and the mauiier of its spread he writes : When the disease made its appearance in this section of country, iu the summer of 18.'>0, and we saw it spreading from farm to farm, the question was .s\iggested whether it did not spread by contagion, for it was not known at that time (July) that the malady was contagious. Feeling much interest in watching the progress of this dis- ease, from the large numbers of animals that were dying, I suggested to the owners of the distillery at Aurora, Messrs. Graffs, that we should try a series of experiments to ascertain the nature of the disease, and whether it was propagated by contagion. To this they readily assented, and as they were constantly receiving fresh hogs, there was a fine opportunity to make any experiments we saw proper. I am indebted to Mr. J. J. Barkman, of Aurora, for seeing that the following experiments, with the exception of the last, were carefully made. The hogs on which the experiments were made were known to be healthy : (1) Six hogs that had been exposed to the malady by being in contact with dis- eased hogs were put into a yard by themselves and fed on slop and corn ; ou the four- teenth day from the time they were exposed to the disease they were all unwell ; 3 died withiu a week afterwards, the rest recovered. (2) Ninety hogs were exposed to the disease, then put into a yard by themselves and fed on corn and water (no slop given) ; in thirteen days disease made its ap- pearance among them, and they continued to die until 60 out of the 90 died. (.3) Fifty hogs were put into a -pen by themselves, and fed on slop ; they had not been exposed to the disease ; for six weeks they continued healthy. (4) One hundred hogs that had not been exposed to the disease Avere put into a yard by themselves, and fed on corn and water; for thirty days no symptoms of dis- ease appeared among them. They were then, put into a pen with diseased hogs; on the thirteenth day they began to show symptoms of the malady, and the disease rapidly spread among them, until 40 died. (5) Thirty-three hogs, out of a lot of 2Q'3, were put into a pen by themselves ; for six weeks they continued healthy. The remaining 230 were put into a pen adjoining in which were diseased hogs; in thirteen days disease made its appearance among them, and continued until one-half died. (6) Four young andhealthy hogs were put into a pen in which, four days previous, diseased hogs had been ; they were fed on corn and water. On the fourteenth day they were all unwell ; and one died on the fifteenth day, and in five days more they were all dead. This experiment shows that the infection may be retained in a pen several days. * North American Medico-Chirurgical Review. 1858, II. 496, 17 (7) I inoculated, on the 28tli of October, five healthy hogs with the blood taken from the inflamed tissues of hogs that had died of this disease. On the fourteenth day (November 11) they were all unwell, and all died with the exception of one. In three inflammation spread from the point Avhere they were inoculated, along the skin and down the legs, which became very much swollen. I can not say that this inflammation was caused by the inoculation, for it did not appear until the fourteenth day, and many hogs had this external form of disease. From these experiments I think that we not only ascertained that this disease was infectious, but that the infection had a latent period of from twelve to fifteen days. Observations have since led me to consider the latent period as varying from twelve to twenty days. These experiments also showed that the hogs in the pens were not dying from strychnine in the slop. A statement was going the rounds of the papers about this time that strychnine was used in making yeast at the distilleries, and was poisoning the hogs at these places in large numbers. The manner in which this disease in many instances spread among hogs from farm to farm also showed most conclusively that it was infectious. One farmer had 75 hogs that he turned into a corn-field to fatten. These hogs had been exposed to the disease, had become sickly, and numbers had died. He bought 36 more; these were all healthy ; they were put into the same field with the diseased hogs ; in two weeks they were unwell, and numbers died. He bought 4.5 more, all healthy, and put them in the same field; in two weeks they began to show symptoms of disease, and in a few days after a number died. Finding that he was likely to lose all his hogs, he sold 50 of the fattest that were left to the butchers in Cincinnati, at a reduced price, as diseased hogs. These hogs, it was said, were purchased for their fat, to be used in the manufacture of lard oil. After deducting the 50 he sold, he lost out of the 156 all but 10. A large number of facts could be given, if necessary, to show the contagiousness of the disease. Hogs that had been once under the influence of this lualady appear not to be susceptible to a second attack. Although placed in pens with diseased hogs they continue healthy and fatten, and not a single instance can I find of hogs having this disease twice. There is reason to believe that this malady occasionally prevails at the distilleries in a mild form, as the old hogs at many of these places did not take the disease. But why it should suddenly have assumed so malignant a character is as difiicult to account for as that scarlatina, from being at one time the mildest of dis- eases, at another becomes one of the most malignant. On the farms the old and young bogs appear to be equally susceptible to the disease. la 1861 Edwiu M. Suow, M. D., of Providence, U. I., contributed a j)aper on bog^ cholera to the Annual Eeport of the United States De- partment of Agriculture (pp. 147-154). The symptoms of the disease he gives as follows : The symptoms, as described by persons unaccustomed to such observations, are ex- tremely various. By combining the information obtained from others with results of our own observations the symptoms, as seen during the life of the animal, are nearly as follows : (1) Refusal of food. — This is the first symptom usually noticed by those who have the care of the animals, though, as will be seen hereafter, this sympton by no means indicates the beginning of the disease. The refusal of food, after it is first noticed, generally continues through the whole sickness, and food of every description is mostly refused. (2) Great thirst. — This is constant, and large quantities of cold water will be swal- lowed if it can be obtained. Even after the animal is unable to stand alone it will drink cold water with eagerness. (3) After a time, the length of which varies very much, the animal begins to show signs of weakness; reels, staggers, and, iu attempting to walk, often falls down. 15612 H C- 2 18 (4) In most cases there is a diariliea, with copious fluid discharges of dark, bilious, and very offensive matters. In a few cases there is no diarrhea, but evacuations of hard blacli balls ; but in some of these cases the fluid offensive matter is found in the intestines after death. (5) In a few cases there is vomiting ; but this is not often severe, nor is it contin- uous for any length of time. (6) The external appearance of the animal is at first paler than usual, but towards the last of the sickness purple spots appear, first on the nose and sides of the head. These extend along the sides of the belly and between the hind legs, after which the animal soon dies. (7) In many eases, perhaps a majority, ulcers are found on the different' parts of the body. These were particularly noticed on the inside of the lips and gums, and on the feet, and were often quite deep and excavated. In some cases these ulcers were seen in the nostrils, and in one case there were extensive ulcerations in the back part of the mouth, on the tonsils. (8) In some cases the legs are swelled, and the animal is lame ; sometimes the ears and sides of the head are swelled and red ; sometimes the eyes are sore and inflamed ; sometimes swellings like carbuncles are seen; and, generally, the glands near the surface seem to be enlarged. (9) In most cases the pulse is quickened, the breathing is hurried and difficult, and there is much cough. But in some genuine cases there is no perceptible trouble with the lungs, and no important signs of disease are found in them after death. (10) The duration of the disease in fatal cases, after the first symptoms are noticed, is extremely variable. We have seen some which have died within two or three hours; others have lived many days. It is difficult, however, to fix the time of the appearance of the first symptoms. The first noticed is usually the refusal of food; but it is probable, indeed it is certain, that the sickness is in progress for a consider- able period before the animal refuses food. Cases like the following are sometimes seen : A hog reftses to eat ; it soon grows weak ; staggers in walking ; turns purple on the sides and belly, and dies within two or three hours after the first symptom is noticed. But, on examination after death, extensive disease is fouiid in the intes- tines, or in the lungs, or in both, at a stage of development which must have required many days to reach. The ^os^morfew appearaDces are then summarized in the following language : Having described the symptoms, as seen while the animal is living, I will now give, briefly, the appearances found on examination of the bodies after death : In the course of our investigations, during the last winter and spring, the bodies of nine hogs were carefully examined by Drs. G. L. Collins, J. W. C. Ely, and E. T, Caswell, of Providence, in the presence of several other physicians. A minute ac- count of each case was prepared by Dr. Collins, and published in the Transactions of the Ehode Island Medical Society for 1861. It will be sufficient for the objects of this paper to give a brief synopsis of the diseased appearances which were found in these examinations : Lungs. — Ivl two cases the lungs were healthy. In tlie remaining seven cases one or both lungs were more or less inflamed, having a liver-like appearance, called hepatiza- tion. In some cases the inflammation was more advanced, and the substance of the lungs was breaking down into a mass of disease. In all cases Avhere the lungs were inflamed there was also pleurisy, and the lungs were adherent to the walls of the chest; the inflammation of the lungs and the pleurisy together constituting true pleu-. ro-pneumonia. In two cases there were tubercles, or consumption in the lungs ; but thisi is not uncommon in hogs, and is not supposed to have any connection with the spe-. cial disease we are considering. Stomach. — The stomach and the small intestines were generally healthy. The, stomach was freqently distended with an offensive mixture of food, and iu one casft 19 the inner surface was ulcerated to some extent. In two cases worms were found in small intestines, but this was probably a merely accidental occurrence, and had no necessary connection with the disease. Large intcsiines. — The inner coat of the large intestines was generally inflamed and softened with ulcerations to a greater or less extent, and they were fretiuently so tender as to be easily torn witli the fingers. On account of their diseased condition their inner coat was frequently discolored. The inflammation and ulceration of these intestines are probably the priucij)al cause of the diarrhea in this disease. Kidneys. — These organs were, in every case, much more pale and yellow than natural; this condition was well marked. The live)- and Madder were generally healthy. In some cases water was found in the cavity of the belly and of the chest, and in the membrane surrounding the heart (heart-case). In two cases numerous minute purple spots were seen upon the mem- brane lining the walls of the belly. The urine was often changed from the healthy condition, containing albumen and other diseased products, not, however, noticeable to the eye. Ulcers upon the feet and in the mouth were often found. The brain was not examined, as there were no symptoms observed which seemed to indicate disease of this organ. It may be at times affected, but is probably more rarely so than the other organs of the body. Such are some of the most important appearances which are found on examination of the bodies of hogs which have died with this disease. It will be noticed that three of the diseased conditions I have described are prominent, important, and such as would bo readily recognized by the most ignorant observer. These are, first, the pleurisy and inflammation of the lungs; second, the iuflanima- tiou, ulceration, and softening of the inner coat of the largo intestines; and, third, the pale and yellowish color of the kidneys. One or more of these diseased condi- tions will be found in every case, and in perhaps a majority of cases they will all be found in the same animal. While Dr. Suow admitted the disease to be epizootic he did not con- sider it to be contagious. Indeed, he neither considered epizootic nor epi- demic diseases to be contagions, but, on the contrary, hekl that they were caused by (1) "an epidemic atmospherical poison," and (2) " the local conditions or circumstances adapted to receive and propagate the poison existing in the atmosphere." In 1875 Prof. James Law contributed a paper to the report of the Department of Agriculture giving his observations upon hog cholera, or " intestinal fever in swine," in. which he so completely embraces the knowledge of our swine epizootics as it then existed that his paper is here reproduced in full. It is as follows : Synomjins. — Typhoid fever, enteric lever, tyi)hus carbuncnlar fever, carbuncular gastro-enteritis, carbuncular typhus, pig distemper, blue sickness, blue disease, pur- ples, red soldier, anthrax fever, scarlatina, measles, diphtheria, erysipelas. Definition. — A specific, contagious fever of swine, characterized by congestion, ex- udation, ecchymosis, and ulceration of the mucous membrane of the intestines, and to a less extent of the stomach ; by general heat and redness of the skin, effaceable by pressure; by small red spots, complicated or not by elevations and blisters; by black spots and patches of extravasated blood on the integument, the snout, nose, eyes, mouth, and all other visible membranes, and on internal organs, iueftaceable by Ijressure and tending to sloughing; usually by licjuid and fetid diarrhea; and by a very high and early mortality. The malady has been long known to pig-raisers and pork-factors in the Old World and the New, but in veterinary works it has been mistakenly placed in the list of malignant anthrax affections, to which many of its lesions bear a striking resem- 20 blauce. Two iluglish works, piiblislied withiu the last year, repeat this time-lionored fallacy. To malignant antlirax it is allied by the altered condition of tbe blood, by tbe solution of the blood-globules, by the imperfect coagulation of the blood in many cases, by the occasional enlargement and congestion of the spleen, by the extrava- sation of the blood out of the vessels (petcchi:e) into the skin, mucous membranes, and internal organs, and by the dusk^^ hue of the eye, nose, etc. That it is essen- tially distinct is shown by the fact that its virus, so frightfully contagious and fatal to pigs, is not communicable to any other domestic animal. The contagion of malig- nant anthrax, on the other hand, is deadly to all domestic animals, and even to man himself. The common American designation of hog cholera has only the diarrhea to support itj and, as we see outbreaks in which this feature is mainly remarkable for its ab- sence, the name comes to be an absolute misnomer. In many cases a gelatiniform exudation takes place on the affected surface of the mucous membrane of the intes- tines, windpipe, or bronchia, and the disease has accordingly been named diphtheria. But as such an exudation is by no means constant, a name founded on this peculiarity would have no actual foundation in a large proportion of cases. Again, the exuda- tion (see Post mortem No. 1) is mainly composed of cells and granules, with less of the fibrinous matrix than is usual in diphtheria. Lastly, the intestinal fever of swine is most virulently contagious, whereas diphtheria is very slightly, if at all, infec- tious, and is confined rather to certain insalubrious localities or buildings. From scarlatina and measles it is sufficiently distinguished by the constancy of the intestinal legions, though it resembles both in its cutaneous rash. With erysipelas it has no real connection, the one common feature, the redness of the skin, being due to a condition altogether different in nature, progress, and results. The constancy of the congestion, specific deposit, and ulceration in the intestines in the fever of swine, characterize it as perfectly as do the same lesions in tyjihoid fever in man. It further agrees with typhoid. fever in having a higher evening than morning temperature and a rose-colored eruption on the skin. To this disease, indeed, it bears a closer resemblance than to any other disorder of man or beast, so that Dr. Budd and others with much plausibility call it the typhoid fever of pigs. But in spite of the similarity of the sj^ecific deposits and ulcerations on the intestines, those of the pig show less tendency to attack the agmiuated glands (Peyer's patches) and the solitary glands than is the case in man. They appear on all parts of the mucous membrane of the large and small intestines, yet the agmiuated and solitary glands rarely escape entirely, and sometimes they alone are the seats of ulceration and morbid deposit. The skin eruption, too, in the pig-fever is often distinctly raised, and even vesicular, whereas that of typhoid fever is a simple rash, and, like a blush, may be com- pletely though temporarily efiaced by pressure. Finally, the contagion is incompara- bly more virulent and tenacious of life than that of typhoid fever, and the mortality is greater and occurs earlier in the disease. On the whole, we must look on this aftection of pigs as a disease sui generis, having close afiSuities with the typhoid fever of man, yet essentially distinct, and hence the term intestiua' fever of swine is more applicable, as at once expressing its nature and avoiding confounding it with otlier and distinct affections. Inciibalion. — The period of incubation has not been definitely settled. My experi- ence in Scotland in 1864 would have led me to set it down at from seven to fourteen days. The infected jiigs were four days on the journey from the English market by rail and seven days on the farm before the disease manifested itself. Again, the home-bred swine were sound until four weeks after the strange hogs came on the farm, and three weeks after the latter were generally sick. Pigs, though farrowed by sick dams, did not show any sign of disease for about a week, although nearly all eventually died. In Dr. Budd's cases, in April, 18C5, the fir^t symptoms of illness were shown four or five days after the pigs were brought from Bristol market, where they may or may not have been infected. 21 Dr. Sutton'a experimeuts, made at Aurora, Intl., in Septoiiiber, October, aud Novem- ber, 1848, deserve repetition in this couneetion. (1) Six hogs, after contact Avith dis- eased animals, were placed in a sound pen, aud sickened on the fourteenth day. (2) Of 90, similarly expostd and then put in a sound yard, some sickened ou the thir- teenth day. (3) One hundred, similarly exposed, contracted the disease ou the thirteenth day. (4) One huudred and thirty, jihiced in a yard adjoining one occu- pied by diseased hogs, became ill on the thirteenth day. (5) Four young aud healthy pigs, placed in a pen occupied four days previously by diseased hogs, sickened on the fourteenth day. (G) Five healthy hogs, inoculated with the blood from the inllamed tissues of diseased swine, were unwell on the fourteenth day. Further experiments were made by Proftssor Axe, of London, in April, May, June, aud July, 1875. (1) Two healthy jiigs wei'c (in April) placed for forty-eight hours in the same house with a diseased one, contact being carefully avoided. One was dull and otf its food on the sixth day and the other on the eighth. (*2) Ou May 15 a pig was inoculated with the liquid cutaneous exudation, which had been kept on dry ivory points for twenty-six days. On the fifth day there was slight dullness and heat of skin, aud on the sixth the malady was well developed. (3) Ou June 10 another pig Avas inoculated with the cutaneous exudation of the last, the opera- tion being performed by another party and the i)ig kept apart to avoid all risk of indirect contagion. On the fifth day temporary redness was noticed on four teats, and on the sixth day the symptoms were fully developed. (4) Another pig broke into the pen occupied by the last-named subject and was left there for six days, when it was taken out seriously ill. In the hot summers of Illinois instances are met with in which symptoms of the disease are shown in a previously healthy herd under three days after the wind has blown from the direction of a sick lot half a mile distant. In analyzing this apparently somewhat discordant evidence we must bear in mind that the period during which a poison will remain latent in the system will vary accord- ing to the amount taken in, the excited or febrile condition of the subject, and the mode of introduction into the system. Thus an excess of any poison, animal or veg- etable, will usually show its etfects with remarkable rapidity. A feverish state of the system, whether induced by intense heat, passion, or disease will rouse the poison into unusually early activity. Lastly, poisons that are inoculated usually act sooner than those introduced into the system by other channels. These considerations will serve to reconcile the prolonged latency of the poison in Dr. Sutton's cases, observed in cold weather, as compared with Dr. Budd's, Professor Axe's, and my own, in the English summer, and of these in their turn with the iirorapt development of the malady in the semi-tropical summer of Illinois. Stjm])io7ns.— The earliest symptoms are slight dullness, with sometimes wrinkling of the skin of the face as if from headache ; shivering or chilliness and a desire to hide under the litter are not uncommon. Some loathing of food, intense thirst, elevation of the temperature of the rectum to 104° Fahrenheit and increased heat and redness of the skin are usually the first observed symptoms, and occur one or two days later than premonitory signs above mentioned. The increased heat of the skin is especially noticeable inside the elbow aud thigh and along the belly. By the second day of illness the whole surface feels hot, and in white pigs is suifused with a red blush, which may pass successively through the shades of purple and violet. It is usually more or less mottled at particular points, aud a specific eruption appears as rose-colored spots of from 1 to 3 lines in diameter, sometimes slightly raised so as to be jjerceptible to the touch, aud either pointed or more frequently rounded. The redness fades under the pressure of the finger, but only to re-appear immediately. The eruption is usually abundant ou the breast, belly, and haunch, the inner side of the forearm and thighs, and the back of the ears. It stays out for two or three days, and may be followed by one, two, or more successive crops of the same kind. The cuticle is sometimes raised in minute blisters, a feature which distinguishes this from the rash of typhoid fever, and the liquid of such blisters inoculated ou other pigs 22 communicates tlio disease. In addition to the rasli and simultaneously with it, or soon after, there appear on the skin numerous spots of a dark-red or black color, vary- ing in size from a line to an inch in diameter, on the color of which pressure has no etfect. These are due to the extravasation of blood or of its coloriiig matter from the blood vessels into the tissues, and they dry up into thiu scabs or slouglis if the ani- mal survives. Similar petccchial spots appear on the muzzle, in the nose, and oh the eyes, and in some instances they are confined to these parts. The tongue is covered by a brownish fur. From the first the animal is sore to the touch, but as the disease develops the handling of the animal is especially painful and causes grunting and screaming. The pig lies on its belly, and, if compelled to rise and w^alk, moves stiffly, feebly, unsteadily, and with plaintive grunting. This weakness aud prostration rapidly increases, and often ends in utter inability to rise or to support the body on the hind limbs. A wa- tery discharge from the nose, followed by a white muco-purulent flow, is not uncom- mon. A hard, barking cough is frequently present from the first and continues to the last. Sickness aud vomiting may be present, but are far from constant. The bowels are often confined at first, and in certain cases, and even in nearly all the victims of particular outbreaks, may remain so throughout, nothiug whatever being passed, or only a few small black pellets covered by a film of mucus. These cases are quickly fatal. More frequently, however, they become loose by the second or third day, and diarrhea increases at an alarming rate. The XJassages are first bilious and of a light or brownish yellow when not colored by ashes, charcoal, or the nature of the foo I. But soon they assume the darker shades of green and red, or become quite black aud intolerably offensive. In such cases the elements of blood, inspis- sated lymph, and membranous pellicles, sloughed off from the ulcerated surfaces, are usually to be found in them. The diarrhea becomes more profuse, watery, and fetid ; the pulse siuks so as to be- come almost imperceptible; the cough becomes more frequent, painful, and exhaust- ing; the breathing is more hurried aud labored; and the weakuess iucreases until the patient can no longer rise on his hind limbs. At this period the petecchite become far more abundant. Before death the animal is often snnk in complete stupor, with, it may be, muscular jerking or trembling, or sudden starts into the sitting posture, and loud screams. In the last stages involuntary motions of the bowels are common. Exceptionally swellings appear on the flank, with extreme lameness, aud extensive sloughs of the skin of the ears or other parts. Palpitations of the heart also occasion- ally occur as precursors, attendants, or sequels of disease. If the disease should take a favorable turn, slight causes maj' make an early and perfect recovery, a complete convalescence being established in three or four weeks. A considerable proportion of the survivors, however, linger on in an unthrifty condition for months, evidently suffering from the persistent ulceration of the intestines or infiltration of the lungs. The mortality often reaches 80 or 90 per cent, of all swine exposed, and in case of a certain number of the survivors recovery brings no profit to the owner. Post-mortem apjiearances. — The blue color of the skin becomes deeper aud more uni- versal a few hours ifter death. The fat beneath the skin is colored more or less deeply in points corresponding to the discoloration of the integument. The snout is usually of a deep bine, with ineffaceable black spots (petecchiai). The membrane lining the eyelid, -and to a less extent the skin, present similar black spots of extrav- asation. The most constant chauges are in the mucous membrane lining the alimentary canal, and especially that of the terminal portion of the small intestine (ileum) aud the commencement of the large (crecum, colon). The tongue is f nrred, but deep red, even eroded, at its base, and the pharynx and adjacent parts usually studded with petecchiiB. The cavity of the abdomen generally contains a few ounces of reddish serum, which coagulates on being heated. The stomach may show no more than a pink blush, but more commonly it is of a deep red, from congestion, especially to- . 23 vrard tlie pylorus, and its mucous luembrane is oftcu black tbrotigliout from tbe close aggregation of petecchiaj. Tbe small intestines are usually extensively congested, and of a deep red, in many cases approacbing to black, as examined exteiually. Tbeir mucous membrane in such parts is equally bigb colored, studded with petec- cbiiip, and iu some cases lined by a firm, semi-fibrinous exudation. A more constant condition is tbe presence of minute slougbs or erosions in tbe seat of peteccbiie, and of equally small elevations, duo to excessive cell-growtb, l)eneatb tbo epitbelium. These commonly have a whitish center, with a yellowish or red border. Such is tbe appearance in cases that prove fatal within two or three days. In tbose that have survived longer, extensive ulcers appear, of au iuch and upward iu diameter, evi- dently the sequel of tbe petecchia>, and cspcciallj- of the eruption. These ulcers are often covered by black scabs or sloughs, have irregular projecting margins and a variously colored center, consisting of cells iu process of disiutegration. They are sometimes situated on Peyer's patches, but show no very marked preference for those over other portions of the mucous membrane. The large intestines present a similar varying vascularity, discoloration, peteccbiie, deposit, softening, and ulcera- tion. Tbe changes are especially marked iu the c;ecuui and colon and in the rectum close to tbe anus. The solitary glands are often large and open, but the ulcers show no particular preference for tbe points occupied by them. Extensive extravasations of blood into tbe coats of tbe bowels aud ani ounces of a dark bloody fluid. The intestines have a deep florid hue externally. The stomach and the greater part of tbe rectum are pale and without any lesions of the mucous membrane. Close to the anus this 24 membrane is cougested. The stomach coutaius about two poumls of food (boiled potatoes, corn, etc.). The small iutestiues have their nincous membrane thickened, soft, friable, and very red, the shades being lighter or deeper at different points. It presents at intervals spots of a much darker hue, approaching purple, and respect- ively from one to two lines in diameter. The large Peyer's patch on the ileum seems hypertrophied and of a deerp red, especially close to the ileo-caical valve, where it also shows small ulcers. The large intestines have their mucous membrane of a very bright red, soft, friable, and presenting at intervals small ulcers of about a line in diameter, and corresponding apparently to the solitary glands. Some of these ulcers are of a deep red, and appear on the peritoneal coat as dark spots ; others are of a dirty white in the center, with raised red edges, and are not so marked on the perito" neal surface. A small nodule felt through the outer coats is characteristic of both. The contents of the large intestines consist of dark semi-liquid feces, with a great amount of ashes. The liver is variable in color and very friable. Though still warm, it presents small bubbles of gas at intervals under its capsule and throughout its substances. The gall-bladder is half full of a very light-colored yellow bile. The pancreas seem healthy. The kidneys, bladder, and uterus are normal. The pleura and lungs appear healthy, excepting a portion of the anterior lobe of the left lung, which is in a state of spleuisation. The bronchia contains bloody froth, especially in the left lung, and those of the solidified portion contain a white solid substauce, completely filling them, and appearing to the naked eye like a fibri- nous clot, while under the microscope it is found to be mainly composed of small glob- ules about the size of blood-cells. It is disintegrated and i^artly dissolved in a strong solution of potassa. The mucous membrane of the larynx and trachea is cougested and the tube filled with a white frothy mucus of an exceedingly tenacious consist- ency. II. — No. 2. Three months' old female pig, large of its age. Dead twelve hours. liigor mortis well marked. Skin almost universally of a livid hue, but pxirple along the abdomen. Back, white. Profuse eruption over the body, but especially abundant on the abdomen. The smallest, and evidently the most recent specimens of the eruption, are individually about a line in diameter, deep purple, and covered by a delicate, slaty-looking skin. The larger sjiots have a dark, hard, dead center, which appears to spread gradually to the whole of the jiatch ; some appear as a large black scab of one-half to 1 inch in diameter. Abdomen contains G ounces of serum, which forms a solid coagulum on being heated. False membranes bind the large intestines to the lower wall of the belly, also the two horns of the uterus together and to the bladder, and both to the walls of the pelvis. The large intestines are the seat of an exudation half an inch thick, from which a straw-colored fluid escapes on section. The stomach is considerably dis- colored on its great curvature externally, as if from extravasated blood. The mucous membrane of the stomach presents numerous petecchiie and ramified redness along the great curvature. The small intestines show slight branching redness o& part of the ileum. Large intestines. — Ctecum has its mucous membrane abnormally vascular; with abundant j^etecchiaj, and ulcers of considerable standing ; these appear as white, raised masses, and have no manifest connection with the solitary glands. The blind- gut contains numerous ascarides. The mucous membrane of the colon repeats that of the c£ecum, but at one point beneath its serous coat is a blood-clot measuring 1 inch by half an inch, and a quarter of an inch thick. The liver is healthy. The diaphragm has abundance of petecchia? on its posterior surface, especially on the cordiform portion, and ajvparently leading in radiating lines from the center. Beyond the presence of petecchiie the organs of the chest seem to be little affected. Causes, — Contagion is the main cause of this disease. The introduction of diseased pigs into healthy herds ; the placing of healthy pigs iu pens, cars, steam-boats, mar- kets, etc., where diseased swine are then or have formerly been exposed; afresh breeze from the direction of a diseased herd, though half a mile distant ; the passage of men or quadrupeds or birds from the diseased to the healthy ; the use of food, litter, or water that has been in near proximity to the affected animals, have each served to transmit the tcver. The virus appears to be concentrated in the bowel-discharges and liquids of the eruptiou, but doubtless exists iu all the liquids aud tissues of the body, and is given oft' into the air from the skin and exposed mucous membranes. Pigs are often born sick, aud die in twenty-four hoars. The feeding-troughs aud water, contaminated by the (ilthy feet aud "snouts, are particularly liable to convey the disease. The n)alady prevails at all the periods of the year, but it has opportunities for the widest dift'usion iu dry seasons aud countries, where the virulent matter may be dried up and preserved unchanged for an indefinite period, and in this state may be car- ried by winds and otherwise. Wet weather contributes to the decomposition and destructiou of this, as of any other animal poison, but can not influence its propa- gation by the direct contact of healthy with diseased animals, nor affect its preserva- tion inside dry buildings. Unwholesome conditions of life contribute largely to its diffusion, if not to its de- velopment de novo. The malady frequently appears in pigs that have been carried several days in succession in crowded boats or cars, among the accumulated filth of their own bodies and those of their predecessors, and subject to compulsory absti- nence from food and water. Again, it will ocour in fat hogs that have been driven a number of miles under a hot sun and then cooped up iu a filthy, close, ill-ventilated pen, subjected to the reeking fumes of their own bodies and of long-accumulated uastiness. Many think that dry-corn feeding and overcrowding on filthy manure heaps are largely productive of the disease. But it is too much to assume that the poison is developed (7c )iovo in such conditions. Similar unwholesome influences favor the development of all contagious diseases by loading the blood with eftete and dele- terious organic matter, and bringing about a feverish and susceptible state of the system. But, on the other hand, such abuse and maltreatment fail, in very many cases, to induce the affection, so that we are left in doubt in regard to those instances in which it appears as to whether the virus was not hidden away in the buildings, cars, etc., and roused into activity by the presence of a fertile field for its growth in the bodies of the pigs, the blood of which was loaded with organic elements in proc- ess of decomposition. The important iioint is this: We know this as a contagious affection, to the propagation of which all probable insalubrious conditions contribute. So soon as we couceutrate our atteution on this point we have the key to its preven- tion, if not to its entire extinction. But, while admitting the iufluence of over- crowding, filth, starvation, and suffering iu predisposing to this disease, it ought to be added that the very highest mortality is often reached among pigs kept in the best hygienic conditions, but among which the virus has been accidentally intro- duced. Again, some hogs, and even families, appear to be insusceptible, and resist the j)oison which is carrying off all around them. But similar instances of immunity are met with in all contagious affections. Treatment. — In a fatal contagious disease like that under consideration it is rarely good policy to subject to treatment. The enormous iucrease of the poison in the bodies of the sick, aud the extreme danger of its diffusion through the air, as well as on the feet of men and animals, render the preservation of the victims eminently un- safe and unprofitable. Yet, iu the case of very valuable animals, and where seclu- sion, disinfection, and careful nursing can be secured, it may be resorted to. A dry, airy, well-littered building may be provided, abundantly spriukled with a solution of carbolic acid or chloride of lime. Rugs steeped in a solution of one or other of these agents may be hung up at intervals, and sulphurous acid set free by burning a piuch or two of sulphur three or four times a day. The dung should be 26 saturated or thickly sprinkled with fiuely powdered copperas. Auy drains will re- quire disinfection in the same way. If the sick animals are kept in tlie open air, the ground must he freely sprinkled with disinfectants, above all where the dung has been deposited. The diet should he well boiled gruel of barley, rye, or Graham ilour; or, if fever runs high and the temperature is raised by such food, corn-starch made with boiling water or milk may be substituted. Fresh, cool water should be freely supplied, either pure or slightly acidulated with sulphuric acid. During the early stages, while constipation exists, the bowels may be gently opened by castor oil (2 ounces for a good six-months' pig) or rhubarb (1 dram), aided by in- jectious of warm water. The heat of the skin must be counteracted by spongiug with cool or tepid water, as may seem most agreeable to the patient. As the laxa- tive operates, 20 grains of uitrate of potash and 10 grains of bisulphite of soda may be given twice a day in the drinking water. Charcoal may also be given to absorb aud neutralize the deleterious products in the bowels. Or the uiter may be replaced by any other neutral salt and the bisulphite by another antiseptic agent. If the pa- tient survives the first few days and gives indications of ulceration, by tender abdo- men, diarrhea, and the passage by the bowels of membranous sloughs, oil of turpen- tine, in doses of 15 or 20 drops, may be given, shaken up in milk or beaten in an egg ; or this nifiy be replaced by similar doses of creosote or carbolic acid, or 3 to 5 grain doses of uitrate of silver. It may he necessary to give opium to check excessive purging, or stimulants to sustain the failing strength and very prostrate condition. Infiltrations and intlammatious of the lungs aud bowels may demand applications of mustard aud turpentine to the chest or abdomen. In short, any complication must be combated as it appears, aud the soundest judgment will be wanted throughout to adapt the treatment to the various indications. Each case will demand as close at- tention and as careful an adaptation of remedial measures to its diii'erent stages and phases as would a case of typhoid fever in man. In case of recovery a course of tonics (gentian one-half dram, sulphate of iron 10 grains daily) will often be beneficial, and the return to ordinary feeding should he brought about by slow degrees. Prevention. — A successful system of prevention can only be instituted when we duly appreciate the fact that almost all cases of this intestinal fever are due to contagion. And this is precisely what our hog breeders fail to realize. No man in his senses will affect to deny that the disease is contagious, but the natural tendency is to seek for other causes in the great majority of cases. As in the case of all contagious affections that have attained a wide prevalence, this iiresents a number of outbreaks which can not be traced to contagion from any diseased stock, and these are at once assumed to be spontaneous, and the cause of the disease is sought in the peculiar treatment of the herd, aud future prevention is attempted by the avoidance of these peculiarities. In illustration, I may quote from a letter of Mr. I. F. Hatch, an intelligent lUiuois farmer, and former student of Cornell University : In former years hog cholera has been local with us except when it first appeared, some ten or twelve years since. Then, as now, it was general, aud swept everything. But since then it has been confined to a few farms or localities. Sometimes it ap- peared on a single farm, or perhaps on several farms, 1, 2, or 3 miles apart, all others escaping. I have a ueighbor who has had it every second year since its first apppear- auce, losing more or less hogs each time, but his is the only case of which I have been informed where it has been so regular and often. This irregularity and local appearance deluded us into the belief that we were pre- venting the disease by extra care and attention, and that salt, sulphur, aud ashes were a preventive ; but we have been eftectually undeceived this time, for hogs that have been doctored thus fared no better than those that had not. There is one man here whose hogs have escaped the disease entirely, and he has fed for a number of years once a week, or once in two weeks, corn boiled in the ear with ashes — lyedcorn, as they call it — putting a peck of wood-ashes into a 40-gallou kettle. He tells me he has had no cholera since he adopted this plan, and his hogs are certainly good subjects for cholera — poor, half-fed, and sleeping in a pile under the barn. He says others have tried this plan and successfully warded off the disease. 27 He goes ou to quote iustauces of .illegetl prevention byfeevliug house-slops ■without corn, and by giving once a week a feed of the boiled jowls and waste parts of the pigs killed the year previous, and adds: Generally diseased hogs run, sleep, and eat with the others, it being the general opinion that they'll all have it anyway, so no matter. I ani of a dilferent opinion. A few change the yards and sleeping places, but generally they stay in the same places throughout the disease. No attention is paid to disinfection. These alleged preventives are doubtless somewhat beneficial by maintaining a free action of the bowels and kidneys, and favoring the elimination of the poison, as does diarrhea in the milder cases of the disease. But there need be as little doubt that, like the salt,- sulphur, and ashes, they would all fail in the presence of a strong dose of the poison. Meanwhile, they are made to serve an evil purpose in diverting attention from the one etfectual means of restricting the disease, the extinction of the poison. It must be fully recognized that neither contact nor proximity is neces- sary to contagion. The poison may be carried a certain distance on a stream of water without losing its vitality. It may be blown a long way by a favorable wind, when dried, up, on light objects. It may be carried on the boots, hands, etc., of men (dealers) passing from farm to farm and from district to district. Horses, cattle, sheep, dogs, fowls, pigeons, and wild animals of all kinds are liable to carry the virus ou their feet and limbs, and to deal out death to the pigs at places widely separated from each other. It is, therefore, quite impossible to trace all new outbreaks to con- tagion. But to attribute them to spontaneous evolution of the disease is to beg the whole question. It can be freely conceded that a certain number of cases probably originate spon- taneously every year ; but these arc few and far between as compared with the enor- mous mortality caused by contagion. It can be equally conceded that certain seasons are far more favorable to the propagation and virulence of the disease than others, yet even in these the great uiajority of cases are infectious. It can be admitted even that a wholesome laxative diet is to some extent protective, as well as comfortable dwellings and antiseptic agents, like copperas, bisulphite of soda, charcoal, or car- bolic acid. But all .such protectives are comparatively limited in their operation, and, though they seera to have saved a few isolated herds, will fail disastrously if generally relied on. The epizootic influence, too, though apparently all-powerful in localities where the poison has already penetrated, fails to produce the disease in the neighboring States not previously infected. We can not give too much attention to secure the best sanitary conditions of life for the hogs, but if we allow a few of these so to engross our attention that our eyes are blinded to the most important of all — the prevention of contagion — we shall only spread the poison and increase the de- struction of our herds. On the other hand, the highest success must attend such measures as will stop the production of the poison and destroy and render innocuous what is already in existence. Diseased pigs must be removed from the healthy, killed, and buried. A thorough disinfection of all buildings, yards, and manure must be made. Chloride of lime or zinc, sulphate of iron, or carbolic acid may be used for all solids, floors, troughs, walls, etc., and for drains ; and sulphurous acid or chlorine for the atmosi)here. The sulphurous acid may be produced by burning sulphur,.and the chlorine by adding oil of vitrei to common salt and a little black oxide of niauganese. The surviving pigs must be carefully Avatched for the first signs of illness. Any unusual sluggishness, stiffness, or inapjietence, or .any disposition to leave the herd, demands a careful ex- amination ; and if there is heat or shivering, and, above all, if the thermometer in- troduced into the rectum indicates a temperature above 103^ Fahrenheit, the animal should be at once separated from the herd, and destroyed as soon as uuequivocal symptoms of the malady are shown. Care should be taken to avoid the possibility of contamination by Avater which has passed infected hog-pens or fields. If the malady exists within a wide radius, the visits of dealers and others must be absolutely for- 28 bidden, and a similar probibitiou sbould attacb as far as possible to quadrupeds aud birds, wild and tame. Disinfectants may even be given to the sound animals that have been exposed to contagion. A table-spoonful of charcoal, animal or vegetable, may be given daily to each pig in its food. Twenty grains of bisulphite of soda, or ten drops of carbolic acid, or 10 grains of sulphate of iron may be used instead, and a tea-spoonful each of 8ul})hur aud gentian may be added with advantage. When a herd has been freed from the disease, a most exhaustive disinfection of the whole premises, manure, aud other products is imperative, aud it is usually desirable to change the site of the hog-pen and run to obviate any future effects of this most virulent conta- gion. Old and rotten wood work should be burned. In purchasing pigs, buyers will consult their interests by avoiding markets, and going rather to the breeders whose stock is known to be healthy, aud by seeing per- sonally to the thorough cleansing and disinfection of loading-banks, cars, boats, etc., which they must use iu bringing them home. And after all such iirecautions, newly purchased swine should invariably be jdaced in quarantine, at a safe distance from other hogs, and kept there for three weeks, with separate atteudants, until they have been proved sound. As in the case of other fatal contagions, this could doubtless be kept iu check, or even completely extinguished, by a uniform system of destruction of the infected, and disinfection of their cai'casses aud all v/ith which they have come iu contact. Such a proceeding would imply an amount of governmental supervision and pecuni- ary outlay that would be profitable in the long run, though the jiast experience of the American people have scarcely prepared them to sanction it. Ill 1877, a paper written by H. J. Detmers, V. S., giving his obser- vations of the disease generally called Log cholera, aud bis conclusions as to its nature, was reprinted in the aunual report of the Department of Agriculture. Dr. Detmers proposed to call the malady "epizootic influenza of swine," aud he divided it into (1) " the catarrhal rheu- matic form," (2) " the gastric-rheumatic form," (3) " the cerebro-rheu- matic form," and (4) "the lymphatic-rheumatic form." The causes of the disease he divided into three classes, and he writes : As belonging to the first class I look nj)on everything that will interrupt or disturb the perspiration ; in the second class I place all such noxious influences and agencies as interfere directlj' with the process of respiration ; finally, in the third class, I put all such noxious agencies or injurious influences as tend to aggravate the disease if already existing, by aiding in making its character more typhoid, or which produce a special predisposition by weakening the constitution of the animal. In regard to the contagiousness of the affection he says: Still I think the epizootic character of the fearful spreading of the disease can be satisfactorily explained without the existence of a contagion. The above extracts show the most divergent views among physcians and veterinarians as to the cause and nature of the epizootics among swine. At the same time'there were equally wide differences of opinion among swine-breeders and the contributors to the agricultural press. In short, there was the greatest uncertainty and confusion of ideas not only as to the characters of the disease or diseases, but as to the most elementary principles to be applied for prevention. It was just at this period (1878) that Congress provided for the first investigation of swine diseases by making an appropiiation of $10,000 for this purpose. The beginning of this investigation, which has been 29 continued with sliort interruptions until the present time, marks a new era in our knowledge of swine epizootics and of contagious diseases in general. It was just at the time when the biological researches of Pas- teur in regard to fermentation were attracting- so much attention, and had already inspired Lister to make his discoveries in antiseptic sur- gery, and Koch to institute those researches which definitely connected the bacillus anthracis with the causation of charbou. The time was propitious, therefore, for the institution of a new line of researches, in a direction which even then promised much, and which since has prac- tically revolutionized the position of medical science as to the nature of contagion and the methods most important for its control. The writings of Drs. Sutton, Snow, and Law gave a very cdrrect state- ment of the symptoms undjwst mortem appearances of the organs usually found in the swine epizootics of this country. The^^ covered about all the points which can be decided by ordinary field observations, but they left many questions still unsolved which it was necessary to determine before measures of prevention could be formulated and made successful. There were many who believed that these epizootics were due to the ravages of more than one disease, and there were also many who held that contagion and infection played no part in their extension. As to the nature of the agent or agents which caused the outbreaks, or the conditions which were required to prevent their destructive ravages, no results of value had been obtained, or indeed could be, without a more systematic and persistent investigation, with all the instruments, ap- paratus, and laboratory facilities which are required to work out the obscure problems of pathological science. As with other contagious dis- eases of men and animals, the instruments of the post-mortem case had been the means by which a certain amount of information had been gained, but there were problems which they could not reveal, and for these the microscope, the culture apparatus, the biological and chemi- cal laboratories were necessary, and without these a reliable solution could not be reached. For the investigutions of 1878 nine men were appointed for a period of two months each, as follows : Dr. II. J. Detmers, Illinois ; Dr. James Law, New York ; Dr. D. W. Voyles, Indiana ; Dr. D. E. Salmon, North Carolina; Dr. Albert Dunlap, Iowa; Dr. E. F. Dyer, Illinois; Dr. A. S. Payne, Virginia ; Dr. J. N. McNutt, Missouri; Dr. C. M. Hiues, Kan- sas. The researches were to be made in the field in different sections of the country, and various remedies, suggested as applicable to tlie treatment of epizootic diseases, were to be tried. The result of this investigation may be summed up practically as follows : (1) Swine dis- eases were found destructive in the most widely separated districts of the country. (2) The symptoms and lesions enumerated were similar to those formerly given by Drs. Sutton, Law, and Snow. (3) No evidence was discovered to show the existence of more than one disease which prevailed as an epizootic. (4) There was a preponderance of opinion that the outbreaks were due to contagion and that the disease was com- 30 municable. (5) The remedies tested eitber produced no effect or were of doubtful vabie for the treatment of affected animals or for guarding against tbe contagion. , Tbere were two points of more than usual interest raised in the inves- tigation. In tbe course of Dr. Law's investigations be made inocula- tion experiments witb rabbits, rats, and sbeep, which he thought dem- onstrated the communicability of the disease that he investigated. Dr. Detmers devoted more of his time to microscopical investigations, and asserted that be had discovered a specific micro-organism, which he called the Bacillus siiis, and that he had demonstrated its pathogenic connection with the disease. Both of these conclusions must now be looked ui)ou as premature and not supported by the direct and positive evidence which is necessary to establish such important points. That Dr. Law produced disease in tbe experimental animals which he inoculated is not to be doubted for a moment, but that it was the same disease and caused by the same microbe which produced the swine eijizootics of the country could only be definitely determined after the microbes of the swine diseases had been identified and their characters established. Very frequently in inoculating with the products of disease taken from dead animals, septic disorders are caused in the inoculated animals which are entirely dif- ferent in nature from tbe malady which caused the death of the indi- vidual inoculated from. To determine, therefore, whether the disease induced is identical with the disease which we propose to propagate by inoculation it becomes necessary to determine the microbe which causes the morbid changes in each case. At that time neither of the microbes which we have since identified and studied in swine epizootics in this country had been discovered, and consequently the line of evidence just indicated was impossible. Dr. Detmers's culture experiments were too crude and primitive to be of any value, even in the condition in which bacteriological science was at that time; and his descriptions of the germ might be applied with equal accuracy to many different species of micro-organisms. For this reason no attempt will be made in this volume to give the details of either the culture or inoculation experiments which he made. While failing to obtain the evidence necessary to establish the connection of any micro organism with the production of this malady, this and sub- sequent reports of Dr. Detmers had some effect in directing the atten- tion of investigators in this country to bacteriological researches as a promising field in which to search for the hidden mysteries connected with this class of diseases.* * It is due to justice to state iu this conuectiou tliat, whereas the appointmeuts lim- ited the work of those selected for the investigatious of 1878 to a period of two mouths, Drs. Detmers aud Law were subsequeutly giveu au opportuuity to coutiuue their iu- Ycstigatlons for a much longer period. It is also jiroper to state that several mouths hefore the investigatious of 1878 began, Dr. Kleiu, of Loudon, had published investi- gatious which he believed established the fact that the swiue epizootics of Great Britain were caused by a baoiUu^i. See Quarterly Journal of Microacopici^l Science, April, 1878. 31 The investigations of tlie Department of Agriculture were continued in 1879 by Drs. Law and Detmers ; in 1880 by Drs. Law, Detmers, and Salmon, and in 1881-'82 by Drs. Detmers and Salmon. The efforts of Dr. Law were largely directed to obtaining a modified virus for prevent- ive inoculation, a doubly difficult and discouraging task before the mi- crobes of the diseases had been discovered and studied. While his results were more or less encouraging, no conclusions of practical value as to a method of preventive inoculation were established. Dr. Detmers continued his microscopic observations and modified his first descriptions of the microbe so far as to speak of it in later reports as a micrococcus. The author devoted the greater part of his time during these years to an investigation of southern cattle fever and fowl cholera, but incidentally investigated a number of outbreaks of swine diseases. He found micrococci in the liquids of the affected animals, which he cultivated and inoculated into other animals, but his results were not sufficiently positive to demonstrate their connection with the disease. There was here a period of about four years when the investigations of swine diseases gave no very decided advance in our knowledge of the subject. The reason for this was that the investigation had been carried about as far as was jDossible by the methods then employed. To get a better insight into the nature of the epizootics and the pecu- liarities of the contagion, it was essential that the pathogenic microbes should be discovered and accurately studied. The investigators saw this and were working in the proper direction, but at that time bacteri- ological science was young and the methods of research had not been clearly worked out. Another and equal difficulty was the fact that the investigators were working without proper laboratory facilities and apparatus for such researches, without assistants, and some of them were devoting much of their time to other duties. Under such condi- tions it is next to impossible to reach successful results in such a diffi- cult field of study. These difficulties were not fully appreciated either by the officials of the Department of Agriculture or by the stock-owners of the country, for the reason that such investigations were new to them and their requirements but imperfectly understood. It was not expected that a chemist would go into a sorghum field and discover the propor- tion of cane sugar in the sorghum cane without apparatus or laboratory facilities, but it was expected that the veterinarian would make much more difficult and delicate investigations than these with no other aids than an ax, a butcher knife, a scalpel, and a microscoi)e. The author saw that jnore facilities must be provided for these in- vestigations, and the work systematized and properly divided, or the final result would be disappointment and failure. It was through his urgent representations that a beginning was made in 1883, by securing an unoccupied room under the roof of the Department buikling, which was fitted up as a laboratory, and by obtaining i)ermission to rent a small place in the suburbs of Washington on which to keep expert* mental animals. 32 The year 1883, however, was one in which the necessity of investigat- ing the prevalence of the hmg plague or pleuropneumonia of cattle became too urgent to admit of delay. There were frequent outbreaks which it was the duty of the chief of the veterinary division to visit and give assistance to the State authorities as to their diagnosis and eradication. This precluded any systematic investigations of swine diseases. The spring of 1884 brought the extensive outbreaks of ergo- tism in Kansas, Missouri, and Illinois, which alarmed the whole coun- try, and which demanded instant attention : and these unfortunately were followed, in the summer, by the outbreaks of pleuropneumonia in Ohio, Illinois, and Kentucky, which required the constant attention of the chief veterinarian and prevented scientific researches for several months. The investigations during the years 1883 and 1884 were, therefore, too much interrupted to allow the number of experiments and the thor- ough working out of details which was desirable. The time was not entirely barren of results, however, in the investigation of swine dis- eases. The laboratory was fitted up and suitable microscopic and bac- teriological apparatus obtained. Able assistants were selected and placed in charge of the different branches of the work. The lines of research were marked out and such arrangements made as would per- mit of the intelligent prosecution of the work, even in the absence of the chief of the bureau. This systematization of the investigations, with the employment of a proper number of persons to keep the different lines of study advancing uniformly, was followed almost immediately by the most important de- velopments. In 1885 a motile bacillus was discovered to be the cause of hog cholera, and its leading characteristics were accurately de- scribed. In 1886 the production of immunity by chemical products was demonstrated, the effect of disinfectants on the hog cholera contagion was thoroughly studied, and the i)resence of swine plague, a second epizootic disease of swine, was discovered. These discoveries solve the most important problems connected with swine epizootics and give a secure scientific basis from which to work in future. In fact these dis- eases are now much better understood than are most of the contagious diseases of people, and the measures applicable, in the present condi- tion of science, to their prevention are equally as apparent as are those which are applied to the plagues of mankind. In the sections of this work which follow the details of the investiga- tions of hog cholera made since 1884 are given as fully as are consid- ered necessary to an understanding of the different phases of the sub- ject. The account of the experiments in regard to swine plague are reserved for publication in a separate volume, which it is hoped will appear within a few months. SYMPTOMS AND POST-MORTEM APPEARANCES IN HOG CHOLERA. The symptoms are uot entirely characteristic, owing to the many forms which the disease may assume. It is moreover quite trouble- some to make careful thermometric aud other clinical observations on swine, which enhances the difficulty of exactly determining the course of the malady. In general we may regard the disease as manifesting itself in an acute and a chronic or mild form. Of the acute form very little need be said. The animals die very suddenly, without having been sick for more than a few hours to a day. The chronic disease may last from three weeks to several months. The animals grow stupid and dull, they refuse to eat, and are ajit to sepa- rate themselves from the rest of the herd. They grow weak, and their movements become slightly tottering. A common symi)tom is diar- rhea, which may appear very soon after the animal becomes sick and last until it dies. In protracted cases the liver may become affected secondarily through the impaired condition of the large intestine. The following symptoms, as noted for three or four years by Dr. Kil- borue at the experiment station of the Bureau, will show how little there is upon which we can depend for a diagnosis during life. The temperature of healthy pigs ranges between 101° and 104J° F. With sick animals it may rise from 1° to 0° above the temperature ob- served in health. Frequently this elevation is absent. During an out- break elevation of temperature may be considered diagnostic, but ab- sence of such elevation proves nothing, since an animal may die with- out having shown any rise of temperature during the disease. There is rarely any cold or shivering stage. The sick animals are dumpish, spiritless, and lie quietly in a corner or huddle together, hiding the head under the litter. They refuse to move even when disturbed, and are more or less oblivious to surroundings. There is more or less loss of appetite. They usually continue to eat a little, however, and often the appetite is scarcely impaired during the whole course of the disease. Acute cases may be seen feeding before they are found dead an hour or so later. In most cases the stomach is well filled after death. The bowels may be costive at the outset or continue apparently normal for some time, or they soon become costive, and remain so in some cases throughout the disease. In the later stages diarrhea of a 15612 H c 3 33 34 liquid, fetid character appears in many cases. The color of the dis- charges depends hirgely upon the feed. In slop or garbage fed pigs they are usually of a dirty black color. In those fed with grain they are light yellowish. The diarrhea persists until death. Vomiting is absent. Eespiration is only occasionally quickened and labored in the later stages. The pulse is more rapid than in health, but its determination unsatisfiictory, owing to the struggle of the animals when held. Cough is infrequent, and then only heard when the animals are aroused, as a single eftbrt or in paroxysms. The skin is frequentl}' found reddened on the nose, abdomen, inside of limbs, the ears, and over the i)ubic region. The redness is diffuse, varying from a slight blush to a deep bluish red or purple. It increases as death approaches, and is usually found at the autopsy. A skin eruption appears occasionally, which is followed by crusts or scabs of varying size. Eeddening of the skin is a symj^ton common to the other swine diseases — rouget and swine plague. The eyes are apt to be watery. This is frequently the first outward sign. Later the discharge becomes thick, yellowish, often gumming the lids together. Towards the end of the disease the animals have a gaunt appearance, with arched back and staring coat. Emaciation is very rajiid. The weakness manifests itself in a staggering, uncertain gait, as if the animal were about to fall. Death ensues quietly. Rarely convulsive kicking is observed. The mortality is very high, usually from 80 to 90 per cent, of those attacked die. These symptoms vary in intensity, and onl}- a certain number are seen in one animal at the same time. In very chronic cases only the autopsy enabled us to make a diagnosis. LESIONS PRODUCED BY HOG CHOLERA. — POST MORTEM APPEAR- ANCES. (See Plates I-VIII iuclnsive.) a. The acute type. — This might with equal propriety be called the hemorrhagic type, inasmuch as the chief and perhaps the only changes are hemorrhagic in character, and these lesions are seen most clearly when an animal is examined immediately after death. The spleen is variably enlarged, soft, gorged with blood. Sometimes it is twice as long as the normal spleen (the other dimensions being proportionately increased), and it may extend across the median line to the right side. Next to the spleen the lymphatic glands and serous membranes are most severely involved. The cortex shows, on section, as a hemor- rhagic line or band, according to the amount of extra vasated blood, or the entire gland may be infiltrated with it. Among the glands most commonly hemorrhagic are those of the meso-colon (large intestine), 35 those at the root of tlie lungs (broncliial), and on the posterior thoracic aorta. Besides these, the retro-peritoneal and gastric ghmds (lesser omentum) may be involved. IVLost rarely the mesentric glands show extravasations to a slight extent. Hemorrhages are also quite frequent beneath the serous surfaces of abdomen and thorax. They are most abundant under the serosa of the large and small intestines as petec- chisB and larger patches. They are occasionally found under the i)eri- toneum near the kidneys, the diaphragm, the costal pleura as extrava- sations nearly an inch across. The lungs, in a small percentage of cases, show subpleural ecchy- moses in large numbers, and on section small hemorrhagic foci are ob- served throughout the lung tissue. In a few cases severe hemorrhages, involving one or more lobes, have been observed. The kidneys are oc- casionally the seat of extensive hemorrhagic changes. The glomeruli appear as blood red i)oints ; larger extravasations occur in the medul- lary substance, and blood may collect around the apices of the papil- Icie. The subcutaneous tissue over the ventral surface of the body may be dotted with petecchiie and occasionally collections of blood (ba^mato- mata) are found in the superficial muscular tissue. The brain and spinal cord have not been examined for want of time. In one case, however, in which they were laid bare, petecchia; were seen on the cere- bellum. The digestive tract usually is the seat of extensive lesions. The fun- dus of the stomach is as a rule deeply reddened ; there may be more or less hemorrhage on the surface, giving rise to patches or larger sheets of blood clots. The small intestine in some cases has submucous eccby- moses throughout its entire length. In the large intestine the ecchy- moses may be so numerous as to give the membrane a dark red ap- pearance. The food is now and then found incased in sheets of blood clot due to hemorrhage on the surface. b. The chronic form is perhaps the most common, at least iu those epizootics which we have studied. The acute hemorrhagic cases usually die in the beginning of an outbreak and are apt to be overlooked. Fol- lowing these are the more protracted, milder cases. In these animals the disease is apt to be limited iu its severe manifestations to the large intestine. The other organs, however, are not exempt from degen- erative changes, owing in part to the impairment of the functions of the large intestine, consequent fermentations and the absorption of poisons thereby produced, in part to the preseuce of tiie specific bacteria iu the spleen and presumably in other organs where they exercise their poison- ous activity. The lesions of the large intestines are necrotic and ulcerative iu char- acter. The ulcers uuiy be isolated and appear as circular, slightly-pro- jecting masses stained yellowish or blackish or both iu alternate riugs. Or they may be slightly depressed and somewhat ragged in outline, 36 When the superficial slougii is scraped away many ulcers show a gray- ish or white bottom. A vertical section reveals a rather firm neoplastic growth, extending usually to the inner muscular coat. When sections of such an ulcer are stained with aniline dyes and examined under the micro- scope w^e notice the submucous tissue very much thickened, infiltrated with round cells, and containing a large number of dilated vessels. Eesting upon this thickened submucosa is aline of very deeply-stained amorphous matter, and upon this is situated the necrotic mass which fails to retain the coloring matter and is penetrated by an immense num- ber of bacteria of various kinds. Frequently ova of trichocephalus are imbedded in the slough. The extent of the submucous infiltration depends upon the age of the ulcer. In old ulcers it contains many newly-formed capillaries, and evidences of the formation of connective tissue are present. The capillaries may extend to the very edge of the border where the slough begins. The latter may have been partly shed, leaving a smooth line bounding the cicatricial tissue. The submucous infiltration gradually disappears as we leave the center of the ulcer, and somewhat outside of the ulcer no inflammation of the membrane is observable. Giant cells may be seen in some cases in the iutertubular tissue at the edge of the ulcer. In very young ulcers it is frequently possible to observe the fundi of the tubules intact, while the inner or free half is converted into an amorphous mass. The depth to which the infiltration extends is not always limited to the submucosa; it may extend into the muscular coats and cause inflammatory thickening there and inflammation and the formation of new vessels in the subjacent serosa. In some cases the necrosis, instead of appearing in circumscribed ulcers from one-sixteenth to one-half inch or more across, involves the whole surface of the mucosa, giving it the appearance of a so-called diphtheritic membrane. In such cases the walls of the intestine are very mnch thickened and so friable as to be easily torn with the for- ceps in handling. Such necrosis is rare in spontaneous cases, but it quite invariably appears in animals which have been fed with pure cultures of hog cholera bacilli. The distribution of the ulcers varies but slightly. They appear most frequently in the ciecum and on the ileo-crecal valve, as well as in the npper half of the colon. The lower half is implicated in severe cases only, and then less extensively. The rectum is only very rarely ulcer- ated. The lower portion of the ileum is ulcerated in a small percentage of animals, especially when they have been fed with hog cholera vis- cera or cultures. The stomach is occasionally the seat of slight ulcera- tion. The lymphatic glands of the affected intestine are usually much enlarged, pale, tough, whitish on section. The spleen is rarely enlarged; the liver shows degenerative changes (softening of the parenchyma, increase of connective tissue). Heart and lungs are usually normal. The lobular pneumonia frequently found in young pigs in the winter 37 months must be ascribed priaiarily to exposure rather Ihau to the (li«- ease, as will be shown subsequently. In some outbreaks the acute and the chronic types of the disease are not so clearly distinct as given in the foregoing pages. Frequently re. cent hemorrhagic lesions seem to be grafted upon cases presenting ex- tensive ulcerations, which certainly are much older than the extravasa- tions. It may be that the latter are the result of a secondary invasion of the hog cholera virus, either from the ulcers in the intestine or from without. HISTORY AND AUTOPSY NOTES OF AN OUTBREAK OF HOG CHOLERA, There is perhaps no better way to illustrate this disease than by giv- ing briefly the history of an outbreak in a single isolated herd. In the following pages are recorded the autopsy notes and the bacteriological examination of such an out])reak near the city of Washington during the months of November and December, 1887. A study of this out- break was taken up to ascertain more especially the condition of the lungs in hog cholera. As it is the fifth or sixth which has been observed during the past three years less attention was paid to careful bacterio- logical observations. At the same time this phase was by no means neglected, as the notes will show. The history of the outbreak as far as could be ascertained was briefly as follows : On October 28, there were in all one hundred and nineteen swine, chiefly young pigs, weigh- ing from 50 to 100 i)onnds. Most of these had been purchased in the city markets. At this same time some twenty boar pigs were castrated. Within two weeks these began to die, and soon after the others took sick, dying at the rate of three to four a day. Less than three weeks after the first deaths only sixty-seven remained out of the one hundred and nineteen. At the end of the year only about a dozen were alive out of the entire herd. These may have acquired immunity. The animals were kept in pens on the top of a hillock sheltered from the weather by large boxes. They were swill-fed, and this may account for their feeble resistance to the disease. In most of them there was a cirrhosis of the liver, with softening of the parenchyma, which was prob- ably induced by the feeding. The origin of the epizootic could not be traced, as the animals had come from various quarters. The city markets had proved themselves in the past the source of disease in several pur- chases of pigs for experimental purposes. The autopsy and bacteriological notes will be given in the order in which the animals were examined, any general remarks being reserved for the end. The rapidity with which the animals succambed to the disease made any very thorough examination quite impossible, since it seemed more desirable to utilize all the material by examining those organs most always diseased in hog cholera. Most attention was paid to the lungs and the digestive tract, while the lungs and the spleen 38 were the only orgaus examined bacteriologically. These notes will serve to supplement the autopsy notes in the reports for 1885 aud 188G. In making cultures from the spleen the following method was usually adopted. At tbe autopsy the abdomen was carefully laid open by first removing tbe skin and then cutting through the abdominal muscles with flamed instruments. The flaps laid back, brought into view the spleen not touched as yet by anj- instrument. It was then drawn out with flamed forceps, severed from its attachments with flamed scissors and placed in a large bottle plugged with cotton wool which had been previously subjected to a temperature of 1500-100° C. for two hours. In this way it was taken to the laboratory and either immediately ex- amined or kept in the refrigerator below SS^* F. over night. In making- cultures the s])leen was placed on a sterile glass support and the surface thoroughly charred with a red-hot platinum spatula. This was always done, although seemingly unnecessary when we consider the momentary exposure to the air in transferring the S[)leen from the abdomen to the sterile bottle. It may, however, destroy any bacteria which have entered the peritoneal cavity through ulcers. Through this charred area an incision or rent was made and a platinum wire introduced, and then a tube of gelatine or beef infusion inoculated with it. When roll cultures were made a minute bit of spleen pulp was torn away from be- neath the charred portion and stirred about in the liquefied gelatine. From this usually a second tube was prepared. Experience of past years had shown that frequently this is not sufficient to insure the fer- tility of the cultures. In chronic cases with tbe spleen but moderately enlarged, hog cholera bacteria are found in very small numbers. lu such cases bits of spleen are cut out trom the charred area with flamed scissors and transferred to tubes of gelatine or beef infusion with or without peptone. Such cultures rarely fail. It might be supposed that the chances of accidental contamination are very great in this pro- cess. But a long experience with spleens of healthy animals and with organs in tbe study of other diseases has demonstrated the entire safety of this procedure, Salmon culture tubes with bits of organs in the bottom covered by nutrient liquids have remained sterile for months in the laboratory. At present the Esmarch tube or roll culture is indispens- able in such cases. In nearly all the cases examined both liquid and gelatine cultures were made. The former permit a diagnosis on tbe following day, while the latter require at least two days, usually three or four, before a re- liable diagnosis can be made. The cultures were always examined un- stained in a hanging drop, as the bacteria in this way are not deprived of their power of motility, which is one of the im])ortant diagnostic characters. Staining cultures was also resorted to, but it adds little in- formation to that gained by a careful examination of the hanging drop. When gelatine cultures were examined the bacteria were always mixed with some sterile beef infusion to bring out their motility. In a number of cases rabbits were inoculated directly Irom lung tis- sue. A small bit, about one half centimeter cube, was torn up with flamed forceps in a flamed watch glass containing some sterile beef in- fusion, and the turbid fluid injected beneath the skin of the thigh. The syringe used was an ordinary hypodermic syringe carefully disinfected by 5 per cent, carbolic acid above and below the piston for one-half hour both after and before use, and each time thoroughly rinsed in boil- ing water. As hog cholera bacteria are destroyed by a 1 per cent, so- lution of carbolic acid in less than ten minutes, and by a momentary 39 contact with water near the boiliug poiut the disinfection was certainly all that could be desired. This method was rejjarded as less open to criticism than the iusertion of bits of tissue under the skin. We still stand in need of a syriuge which can be disinfected without much trouble, as the above method is extremely tedious. The syringes devised by Koch are both unsatisfactory. The joints formed by the glass barrel and the metal cap in the syringe in which the propelHng force is air were found to leak in five out of six samples. From the fluid injected into rabbits either i)late or roll cultures were made in order to get an idea of the approximate number and the kind of organisms present. In every case the portion of lung tissue from which the inoculations were made was transferred to sterilized bottles and protected from ac- cidental contamination as carefully as possible. Unless otherwise indi- cated, the methods just given were employed throughout the investiga- tion. November IC. — Pig No. 1, just died aud brought to experimental sta- tion. No skin lesions; heart and lungs normal with exception of a few colhipsed lobules in principal lobe of one lung.* In abdomen omentum injected so as to appear bright red. Spleen enlarged, soft, dark. Some lymphatics have the cortex hemorrhagic. Stomach and small intes- tines normal. In ctecum near valve several large superficial yellowish ulcers and a number of smaller ones, an eighth of an inch in diameter. Two bits of spleen were cut out and dropped into a tube of gelatine, and one of beef infusion. The gelatine culture remains sterile. The liquid culture contains the motile hog cholera bacteria and a large bu- tyric bacillus growing only in the bottom of the liquid. No. 2 died last night. Buzzards have eaten into the thorax aud i;)enetrated the coats of the stomach. Only the small ventral lobe of right lung diseased. Bright red, mottled with pale yellow dots. (See Plate IX, fig. 2.) The smallest bronchi occluded by cylindrical plugs. Alveoli likewise occluded. The pings consist chiefl}'^ of cells and are so dry and firm that they may be removed as small ramifications or branchings when the lung tissue is torn away. Bronchial glands enlarged, hemorrhagic. Spleen enormously enlarged, liver in advanced stage of cirrhosis. Glands at portal fissure chronically enlarged. In caecum four superficial ulcers one-half inch across, slough stained yel- low. In upper colon four similar to these and a large number of small ones about one-eighth inch across with yellowish slough. A moderate number of bacteria found in cover-glass preparations of spleen. A gelatine tube culture contained, after three days about, sev- enty-live to one hundred colonies of the motile hog cholera bacteria in * Iq order to uuderstaud the description of the Inng lesions, the following brief outline of the anatomy of the lung and of the terms nsed may be of service: The right lung is made up of four lobes ; the left has oniy'three. (In text-books on anatomy the left lung is considered as being made up of only two.) In both there is a large principal lobe resting upon the diapbragm and against the adjacent thoracic wall. This lobe forms the major part of each Inug. The remainder, occupying the anterior (or cephalic) portion of the cavity, is made up of two small lobes, one extending veutrally (or downward in the standing position of the animal) aud in the expanded state covering tiie heart 1 iteraljy, the other extending towards the head and overlapping the base of the heart. These small lobes may be denomi- nated the ventral and cejjhalic lobes, r(\siieclively. The right cephalic lobe is longer and more distinct from the ventral lobe than the corresponding left cephalic. Wedged in between the two principal lobes and resting on the dia|)hragm is a small lobe, pyramidal, belonging to the right lung (azygos lobe). This lobe rests on the left against the mediastinal membrane, and ou the right it is separated from the right principal lobe by a fold of the pleura passing from the ventral abdominal wall to in- close the inferior vena cava. This small lobe is almost completely shut otf, therefore, from the other lobes by folds of the pleura. 40 each ueedle track. A liquid culture inoculated simply with the platinum wire thrust into the spleen pulp contained hog cholera bacteria only. A rabbit was inoculated from lung tissue as above described ; about one- fourth of a cubic centimeter of the suspension injected. Dead on the seventh day. Slight fibrinous exudate on coils of intestines. Spleen very large, soft, dark. Beginning coagulation-necrosis in liver. Bac- teria very numerous in spleen; both gelatine and liquid cultures contain only the motile hog cholera bacteria. The plate from lung tissue with which rabbit was inoculated contains a very large number of identical colonies, made up of motile hog cholera bacteria. November 17. — No. 3, male, died yesterday. Buzzards have consumed pectoral muscles and pierced into thorax and abdomen. Ecchymoses on costal pleura and entire epicardium, a few under pulmonary pleura. Left lung hypostatic, slight amount of whitish foam in trachea. Lung tissue otherwise entirely normal, neither hepatization nor collapse anywhere to be seen. Bronchial glands and those along posterior aorta with hem- orrhagic cortex. Ecchymoses in the subcutaneous fatty tissue over en- tire ventral aspect of body, about one-eighth inch across, beneath peri- toneum of abdominal muscles and of the entire length of small intes- tine, from size of pin's head to one-eighth inch. Congestion in patches in large intestine, no ulceration. Stomach and intestines contain a yel- low liquid resembling the yolk of eggs. Spleen but slightly enlarged. Ecchymoses under serosa of liver. Cirrhosis moderate. A bit of spleen tissue dropped -into a tube of beef infusion gave rise to a culture of hog cholera bacteria. In each needle track of a gelatine culture countless colonies of the motile bacteria appear. November 18. — No. 4, medium sized male, died this morning. Super- ficial inguinal glands enlarged, cortex slightly hemorrhagic. Some fibrils on coils of intestine. Petecchi.e under serosa of small intestine ; extensive hemorrhage between mucous and muscular coat of stomach along fundus, forming a clot about one-half inch thick. Spleen very large, friable, blackish, extends beyond median line into right side. Petecchiie on liver, which- is considerably cirrhosed ; mucosa of stomach along fundus blackish : closely set petecchi;e under mucosa of small in- testine; contents liquid, bloodstained. A dark hemorrhagic patch near valve in large intestine. Colon studded with petecchia?, no ulcera- tion. Small number of petecchioe on surface and throughout cortex of kidneys. No bacteria seen on a cover- glass preparation of spleen tissue. Beef infusion inoculated with a wire thrust into spleen remains sterile. A bit of spleen dropped into a tube of gelatine gives rise to about a dozen colonies of hog cholera bacteria. November 18. — No. 5, male, 75 pounds, three to four mouths old, died last night. Inguinal glands enlarged, pale. Left cephalic, ventral, and about one-third of principal, right cephalic and ventral lobes of lungs solidified, bright red, mottled with minute yellowish dots, i. e., same as No. 2. Costal pleura covered with a very thin whitish exudate. Solidified portion of principal lobe adherent. On epicardium a very delicate papery deposit. Spleen much congested. Inflammatory ad- hesion of liver to diaphragm. Mesenteric glands nearly as large as hen's eggs, mottled, pale red. About twelve ulcers one-quarter to one- half inch across in lower ileum; base depressed and covered with a thin yellow layer; outline irregular; not connected with Peyei's patches. Valve thickened and ulcerated. Several ulcers in c;iecum ; a large projecting slough attached to one of them. A gelatine and a liquid cult- ure from the spleen contain hog cholera bacteria only. A liquid culture from the pleura remains sterile. 41 A rabbit inoculated from thebepatized lung tissue died on the eighth day. Slight fibrinous exudate on intestines, diffuse coagulation necrosis in liver, spleen much congested. Immense number of hog c}iolera bac- teria in spleen and liver. Cultures pure. A ])late made from the same bit of (pig's) lung tissue contains about fifty colonies resembling hog cholera. Ko. 6, large black male, died last night. Extensive sero-fibrinous infiltration of subcutis from axilla to pnbis and over right thigh. The subcutis has a gelatinous aspect. Spleen much congested. Lungs nor- mal. In cover-glass preparations from spleen large bacilli, with ends square. Cultures in gelatine and beef infusion remain sterile. Animal l^robably died of malignant oedema. Noi-emher 21. — Xo. 7, medium sized male, died yesterday. Tempera- ture of air varying from 20° to 50° F. Omentum deeply reddened. Spleen enlarged, soft; small hemorrhages under capsule one-eighth inch across. Liver imparts a sensation of grittiness when cut. Cortex of kidneys dotted with hemorrhagic points. The patch of mucous crypts about valve in caecum dark, pigmented; no ulceration. Mucosa of stomach hemorrhagic in fundus. Thorax half full of blood-stained serum and some fibrin stretching from lung surface to walls ; small quantity of fibrin in pericardial cavity. Lung tissue infiltrated with blood (pulmonary hemorrhage). Two ventral lobes collapsed; subpleu- ral hemorrhagic patches. A cover-glass preparation from spleen con- tains numerous hog cholera bacteria. In each needle track of a gela- tine culture, countless colonies. A liquid culture from a bit of spleen tissue contains hog cholera bacteria only. No. 8, small female, died yesterday. Patches of skin on ventral as- pect of limbs and groin reddened. Minute petecchiai under serosa of ventral abdominal walls. Spleen very large, congested. Some delicate fibrils stretched over coils of intestine. Liver cirrhosed. Crlands of mesentery and mesocolon enlarged; cortex hemorrhagic. Fundus of stomach moderately congested. In caecum are black pigment spots resembling former hemorrhage, chiefly on the summit of folds. In upper colon ulcers about three to a square inch, each one-fourth inch in diameter, and covered by a convex, iirojecting yellowish slough. Ulcers found down to rectum. Small quantity of clear serum and a few fibrils in pleural cavities and pericardium. Left ventral and tip of right cephalic lobe collapsed. A gelatine and a liquid culture made from a bit of spleen tissue contain hog cholera bacteria and a butyric bacillus which slowly liquefies the gelatine. No. 9, small male. Diffuse reddening of ventral aspect of body es- pecially marked on limbs. Spleen, lymphatics, and kidneys normal. A small abscess in pelvis attached to bladder, probably caused by castra- tion. Venous congestion of vessels of mesocolon. The transverse folds of mucosa of colon covered by very thin yellowish patches of ne- crosis. Feces hard, distending the large intestine. Cephalic and ven- tral lobes of left lung solid, plainly mottled. The bronchioles and alveoli filled with consistent plugs of cellular exudate. Remainder of lungs normal. Owing to small size of spleen, two liquid cultures were made, each with a bit of spleen tissue. In both, hog cholera bacteria alone appeared. A rabbit inoculated with hepatized lung tissue re- mains well for weeks after. A plate culture therefrom is liquefied in two days. No. 10, small castrated male, died yesterday. Has been sick for some- time according to overseer of farm. Spleen not enlarged. Inflammatory changes in pelvis due to castration. Stomach slightly reddened and 42 bile stained. One large ulcer on ileo ciecal valve one-lialf inch across, black, with yellowish margin. A few very superficial ulcers in caicum. Lungs normal, lelt somewhat hypostatic. Two cultures made with bits of spleen contain both hog cholera bacteria and butyric bacilli. No. 11, dying, killed by being bled from brachial vessels. Lungs normal. Spleen small. Liver slightly cirrhosed. Two ulceres in ciecum; slight superficial necrosis in colon. A liquid culture made from a bit of spleen contains hog cholera bacteria on following day. November 23. — No. 12, small white male, died yesterday. Median line of ventral aspect of body much reddened, limbs slightly so; ex- travasation under skin and into muscular tissue over sternum. Much blood-stained serum in peritoneal cavity; spleen very large, dark. In kidneys, cortex and base of pyramids deeply reddened. In cajcuu), slight traces of superficial necrosis. Anterior and cei)lialic lobes of both lungs collapsed. Bloodstained serum in pericardium. Numer- ous hog cholera bacteria on cover-glass preparations of spleen pulp. In a gelatine culture from the spleen countless colonies appear in each needle track. A liquid culture made with platinum wire contains hog cholera bacteria on following day. A rabbit inoculated from the col- lapsed lung tissue died on the tenth day. Spleen engorged ; numerous foci of coagulation necrosis in liver, involving each one or more acini; extensive necrosis along border of left lobe. Ecchymosis of pyloric valve and duodenum; hemorrhagic foci in lungs, about fifteen in each lung, one eighth inch to three-sixteenths inch in diameter. Examina- tion of the spleen shows numerous hog-cholera bacteria. A gelatine culture contains countless colonies in each neesed lobules in ventral lobes. Both a gelatine and a beef infusion culture contain hog cholera bacte- ria. Colonies very few\ No. 33, large black and white male; said to have died last night. Advanced j;o,s'^ mortem changes. No examination made, excepting to see the condition of lungs, which were healthy. No. 34, medium-sized w^hite, died last night. Considerable reddening over ventral aspect of body. Inguinals reddened on section. Small quantity of dark-colored serum and numerous yellowish iiaky coagula attached to abdominal organs. Spleen very large, dark, friable. Liver cirrhosed. Kidneys with cortical portion thickly dotted with petecchiie, hemorrhage into pelvis. Lymphatics in abdomen with cortex more or less hemorrhagic. Extensive and deep ulceration in large intestines ; in caecum and upper colon as large patches, in lower colon as small ulcers. The mucosa which is not destroyed is deeply congested. Stomach along fundus deeply reddened. Extensive fibrous adhesions of left lung to walls of thorax. Collapse involves ventral, cephalic, and portions of principal lobe of right lung, and small i)ortion of principal and ventral lobe of left lung. Extensive muco purulent secretion in trachea, bronchi, and subdivisions throughout both lungs. Bronchial glands with cortex hemorrhagic. A beef infusion culture from the spleen contains hog cholera and butyric bacteria. In the gelatine cult- ure each track of the wire contains countless colonies of what are shown under the microscope to be motile hog cholera bacteria. From a bit of collapsed lung tissue a plate culture was made and a rabbit inoculated. The plate develops countless non-liquefying colonies. The rabbit died on the eighth day. Spleen enlarged. Liver infested with coccidia. A 48 sliglit amoimt of coagulation-necrosis. Hog cliolera bacteria in both organs and in cultures from the spleen (both gelatine and liquid), December 5. — No. 35, small black and white female, died yesterday. Eeduess of skin over abdomen and inside of limbs. Spleen enlarged, slightly congested. Lymphatics with cortex infiltrated with blood. Large quantity of blood-stained serum in abdomen. Liver sclerosed. A few scattered petecchiie in cortical portion of kidneys. Mucosa of colon pigmented; a few small ulcers present. Lungs normal, with ex- ception of a few collapsed lobules in ventral lobe of each lung. Dark- colored serum in pericardial cavity. The spleen contains large num- bers of butyric bacilli. A liquid culture contains both hog cholera and butyric bacilli. A gelatine culture remains sterile. No. 36, large black and white female, died yesterday. Lungs normal. Spleen very large, dark, friable. Liver sclerosed; lymphatics gener- ally with cortex congested or hemorrhagic. Large number of ulcers in caecum and colon; mucosa deeply congested. From spleen countless colonies of hog cholera bacteria in a gelatine tube culture. In a liquid culture the butyric bacilli are also found. No. 37, medium Jersey red and the last.of a lot of seven, dead forty- eight hours. This animal has been sick for some time ; the spleen was very large, gorged with blood. Lymphatics pale. Large number of old ulcers, from one sixteenth to 1| inches across in ciecum and colon ; mucous membrane generally pale. Of the lungs, both ventral and a small portion of cephalic lobes with smaller bronchi and alveoli plugged with dry catarrhal products. A liquid culture from the spleen contains hog cholera and butyric bacilli. A gelatine culture contains countless colonies. The spleen pulp on coverglass preparations shows many. From the diseased lung tissue a rabbit was inoculated and a plate cult- ure niade. The latter develops a large number of colonies of hog cholera bacteria. The rabbit died on the eighth day. Spleen enlarged and friable, contains many hog-cholera bacteria. Slight coagulation-necrosis in liver, which is infested with coccidia. Cultures from blood and sj)leen pure. Becemher 7. — No. 38, small white female, died last night. Much ema- ciated. Subcutaneous and subperitoneal tissue contains numerous ex- travasations. Lymphatics in general with hemorrhagic cortex. Spleen moderately congested. Lung tissue normal. Numerous subpleural and epicardial hemorrhages. Kidneys with cortical portion dotted with numerous punctiform extravasations. Mucosa of small intestine con- tains numerous petecchia?. One ulcer, one half inch across, in lower ileum. Exteusiveand deep ulceration throughout whole length of large intestine. Some of the ulcers over 2 iuches across; surface coal-black; the inflammation extending through the intestinal walls to serosa, which is dotted with scattered extravasations. A gelatine tube culture from S[)leen pulp contains countless colonies in each needle track, consisting, as seen under the miscroscope, of motile hog cholera bacteria. A liquid culture contains also streptococci and butyric bacilli. No. 39, black and white female, 2)ost mortem changes under way. No examination made beyond ascertaining that lungs are normal, lym- phatics with cortex infiltrated with blood, and spleen enlarged and con- gested. December 8. — No, 40, small black female, died this morning. Super- ficial inguinals enlarged but pale. Moderate quantity of straw-collored serum in abdominal cavity. Spleen enlarged, deeply congested. In csnecum and upper colon a large number of deep broad ulcers ; in some the inflammation extends through intestinal wall to serosa. In lower 49 colon, ulcers small and mucosa deeply congested. Numerous bog cholera bacteria in spleen as shown by a gelatine culture. A liquid cul- ture contains also butyric bacilli. No. 41, small black and white female, died yesterday. Post mortem changes under way. Large quantity of bload-stained serum in abdomen. Plastic peritonitis matting together the various organs; spleen enlarged and congested. Numerous old ulcers in ciecum and colon, with adher- ent slough. Adhesive pleuritis, with hirge quantity of blood-stained serum in thorax. Lungs normal, excepting areas of collapse in ventral and cephalic lobes. A liquid culture from spleen contains both hog cholera and butyric bacilli. A gelatine lube culture develops a large number of colonies in each needle track. December 10. — No. 42, small black and white male, died yesterday morning. No discoloration of skin. Spleen very large, congested. Lymphatics with cortex slightly reddened. Liver cirrhosed. A few ex- travasations in pyramids of kidneys. Mucosa of ciecum and upper colon covered with ulcers, the adherent slough dirty yellowish. Fully one-half the area of membrane thus involved, the remainder is pale. Lungs normal. From the spleen, hog cholera as well as butyric bacilli appeared in a beef infusion culture. In a tube of gelatine the colonies were very numerous. December 12. — No. 43, small black and white male, died December 10. No discoloration of skin. Spleen xery large, friable, gorged with blood. Iiigninals and lymphatics at lesser curvature of stomach hemorrhagic thioughout. Those of mesentery and mesocolon less so. A few petecchiaj on surface of kidneys. Liver slightly cirrhosed. Mucosa of csecum pale, of colon considerably congested. A few small ulcers with hemorrhagic border. Mucosa in fundus of stomach deeply congested. Slight hemorrhRge in principal lobe of each lung, otherwise both nor- mal. Bronchial glands hemorrhagic. Hog cholera bacteria quite abuu- dant iu spleen, as shown by cover glass preparations and cultures. December 15. — No. 44, medium-sized white female, died yesterday morning. Slight reddening of skin along median line of abdomen, limbs, and throat. Spleen enlarged and engorged. Inguinal, bronchial, retro- peritoneal and meso colic glands with cortex hemorrhagic. Liver badly cirrhosed. In crecum one ulcer an inch across, involving entire thick- ness of wall, and few smaller ones. A few in ujiper colon. Lungs aulematous. At least one-half of each lung (most dependent portion) airless, of a red flesh color. Sprinkled through it in some places more densely than in others are grayish-yellow areas one-half to two milli- meters in diameter. Trachea full of foam. Bronchi contain a thick mucous secretion, most abundant in the diseased region. A roll cult- ure from the spleen contains numerous colonies of hog cholera bac- teria. From a bit of lung tissue a rabbit was inoculated ; a plate culture from the same shows a very large number of colonies, probably hog cholera. The rabbit died on the seventh day. Spleen enlarged. Coagu- lation necrosis in liver, which also contains coccidia. Hog cholera bac- teria numerous in spleen, as shown by cover-glass preparations and roll cultures. . No. 45, large black-and-white female, died December 13. Slight red- dening of skin. Spleen large, congested. Lymphatics in general with cortex hemorrhagic. Liver badly cirrhosed ; surface dotted with hem- orrhagic points. Kidneys on surface and on section, as well as mucosa of cjv'cum and upper colon, dotted with numerous petecchiii'. No ulcer- ation. Large quantity of blood-stained serum and coagula in pleural sacs, chiefly in the right. Lungs not collapsed, iutiltrated with a red- 15012 H c 4 50 dish serum ; left hypostatic. Abuiidaut mucous secretion in bronchi and smaller air tubes stained with blood. No hepatization. Roll cult- ure from a bit of spleen contains a large number of colonies of hog cholera bacteria. The same maybe seen in cover-glass preparations from the spleen itself. No. 4G. Large black-and-white male, died December 13. Spleen en- larged and congested. Abdominal lymphatics with cortex more or less congested. Liver slightly cirrliosed. One large ulcer on valve about 1 inch across; several half as large in the middle of colon. Mucosa deeply congested in cfecum and colon ; much pale serum in pleural sacs. Lungs slightly cedematous. Of right lung the principal near root, ventral and tip of cephalic airless, collapsed. One lobule on ventral (diaphramatic) surface of principal lobe airless, with faint catarrhal in- jection of bronchioles and alveoli ; of left lung a small portion of the principal collapsed; the ventral and cephalic emphysematous. The trachea, bronchi, and branches contain a large quantity of a translucent viscid mucus; no lung worms present. Bronchial glands enlarged, pale; those on posterior aorta with cortex hemorrhagic. Extravasations beneath epicardium. A plate culture from a bit of lung tissue develops about seventy-five colonies of hog cholera bacteria. A rabbit inoculated from the same bit remains well. A roll culture from the pig's spleen contains about fifty colonies alike; one examined is made up of motile hog cholera bacteria. December 17. — No. 47, small female, died yesterday. Superficial in- guinals entirely hemorrhagic. Mesenteric glands slightly congested. Spleen barely congested. Mucosa of lower ileum com])letely ulcerated. Similarly that of csecum and upper colon, but more severely so as to make the intestinal wall very friable. In lower colon the ulcers are isolated. Lungs and heart normal. In a roll culture from a bit of spleen tissue about one hundred colonies of hog cholera bacteria ap- peared. No. 48, medium-sized black-and-white female, died last night. Suj)er- ficial inguinals enlarged, pale. Abdominal lymphatics in general with cortex hemorrhagic. Spleen congested; surface covered with numerous elevated blood-red points. Liver extensively cirrhosed. Mucosa of ileum dotted with petecchiie. It contains about fifteen ulcers, not limited to Peyer's patches, with longer diameter transverse, in some cases encircling the tube. The ulcer is covered by a thin yellow slougli. One ulcer, one-half inch across, in ciecum, and two in colon. About one-half pint of straw-colored serum and a mass of semi- gelatinous i)ale coagulum the size of a list in each pleural sac. Lungs but partly collapsed, pleura slightly roughened. Interlobular tissue of dependent lobes distended with serum, parenchyma cedematous, so as to sink in water. Bronchi contain a slight amount of reddish tiuid. In a roll culture from a bit of spleen pulp about two hundred colonies of hog cholera bacteria appear. Beeemher 24. — No. 49, large, black and white. Spleen gorged with blood. Lymphatics generally pale; liver cirrhosed. Ci^cum and colon with walls thickened and very friable; mucosa entirely ulcerated. One ulcer in rectum. A roll culture from the spleen melted, but found to contain on examination only hog cholera bacteria. DISEASE IN HEALTHY PIGS CAUSED BY MATERIAL FROM THIS EPI- ZOOTIC. A^ovemher 2L — Two pigs (Nos. 434, 435), about two months old, fed with spleens from several of the preceding cases. Two days later a few 51 more spleeus were given them. Both became sick a few days later and died November 28, about twelve hours apart. No. 434. Spleen slightly enlarged, full of blood. All glomeruli of kid- neys show as hemorrhagic points: lymphatics moderately congested. Stomach along entire fundus deeply congested. Superficial small ul- (;ers in ciecum and colon ; in the ciecum they are covered by a project- ing slough. Eight ventral and cephalic lobes collapsi'd, the formei" de- veloped into broncho pneumonia (catarrhal injection of small air tubes and alveoli). A few lobules of left priucii)al lobe in the same condition. Hog cholera bacteria in the spleen as determined by a gelatine and a liquid culture. A rabbit was inoculated with a bit of lung tissue and a plate culture made. This developed countless colonies, non-liquefy- ing, alike, shown to be motile hog cholera bacteria. Kabbit dies on sixth day. Spleen moderately congested; contains many hog cholera bacte- ria. In liver, minute foci of necrosis. A gelatine culture from the spleen contains numerous colonies of hog cholera bacteria. No. 435. Spleen enlarged, covered with hemorrhagic elevations. Kid- neys hemorrhagic as in No. 434. Stomach near pylorus deeply con- gested. CiECum and entire colon covered with a dirty yellowish and blackish slough. Eight and left ventral lobes, a small portion of right principal and left cephalic affected with bronchopneumonia. Cultures from the spleen of this animal were confused with those of another pig (No. 135), but one set remained sterile ; the other contained hog cholera bacteria, and it is highly probable that the fertile cultures belonged to this animal. A few additional cases are cited to show the infectious nature of this outbreak. No. 436 and No. 437 were placed, November 27, in the infected pen containing the two preceding animals. They were also fed portions of hog cholera viscera later on. No. 430 was found dead December 27. Eed blotches on skin of ventral aspect of body. Superficial inguinals hemorrhagic. Other lymphatics enlarged but p?-le. Spleen slightly congested. Mucosa of caecum and colon deeply congested and dotted with considerable number of small ulcers. A roll culture from the spleen melted, but contains only hog cholera bacteria according to mi- croscopic examination. No. 437 did not take the disease. No. 449 and No. 452, placed in the same pen December 17, but not fed with infectious matter, died December 29. The lesions were somewhat different from those usually found, and are briedy as follows: No. 452. Spleen and lymphatics not enlarged. Large quantity of se- rum and fibrinous coagula in abdomen. Viscera generally agglutinated. Lungs glued to chest wall by a recent exudate. Pericardium distended with serum and coagula. Lung tissue not affected. Kidneys deeply reddened. Mucosa of Ciecum and colon entirely covered with a thin layer of diphtheritic exudate ; when scraped away a deeply reddened surface is exposed. Numerous small, deep ulcers present. A roll cult- ure of si)leen,also melted from the heat of laboratory, contains only hog cholera bacteria. In No. 449 the lesions were the same, excepting the pericarditis. The ulceration of large intestine less extensive. Two very instructive cases of hog cholera were caused by simply ex- posing pigs on an infected asphalt floor in a pen adjoining cases of the disease. No. 404 and No. 400, about three and one-half mouths old, exposed with six others January 4. No. 404 died January 11. Superficial inguinals 52 noruial. Those in abdonieu much tumelied and lieniorrbagic tlirongh- ont. Si)leen enlarged, friable, with Leinorrhagic points. Several patches of mucosii in fundus of stomach one-fourth to one-half inch across, covered with blood clots. In large intestine oul}^ a few scattered petec- chiic on mucous membrane. Some subpleural hemorrhages in kings; lung tissue normal. Scattered petecchia) on epicardium of auricles and ventricles. On cover glass preparations from spleen pulp a moderate number of bacteria were present. In several roll cultures only colonies of hog cholera bacteria appeared. No. 40G died January 13. Skin of ears, throat, nose, limbs, and belly le collapse or lobular broncho pneumonia following it. Simple collapse usually involved the two ventral dependent lobes more rarely portions of the small cephalic and the principal lobes. The collapsed lobes, or groups of lobules interspersed among emphysematous lobules, appeared slightly, if at all, depressed. The color appro:, died that of red flesh. In only a few instances could plugs be found occlud- ing the bronchi. Sections made from lobules in this condition show a number of interesting features. The alveolar walls are crowded together in some places till they almost touch one another. Besides the fibrin, there may or may not be one or several large cells, round, with much protoplasm inclosing a vesicular nucleus. The bronchi are all open; the epithelium intact. The alveolar walls are not changed, nor is there any round cell infiltration to be seen. In circumscribed areas the capil- lary net-work is distended with blood corpuscles, while all the larger vessels are similarly filled with these elements. In the alveolar duct there is now and then considerable fibrillar fibrin well brought out by Weigert's stain. In about 15 per cent, of the animals examined one of the smaller ventral lobes was airless throughout and moderately enlarged. Viewed from the surface, the diseased lobe is bright red, dotted with minute, pale grayish or yellowish points of a diffuse hazy outline, each not more than 1 n.iiUimeter (J^ inch) in diameter. They are usually arranged in groups of four, and represent the ultimate air-tubes filled with cel- lular exudate. The larger bronchi are also occluded. The exudate is yellowish white, so firm tiiat it is possible to tear away the lung tissue with needles without necessarily breaking up the inclosed exudate. It may thus be teased out in the form of l)ranching cylinders, becoming smaller, and finally dwindliug down to the size of a coarse hair. In microscopic sections the alveolar walls are found beset with dis- 65 tended capillaries. The alveoli are filled up with cellular masses, fibrin appearing very rarely. In most alveoli the cells are large, round, with vesicular nucleus, cviilently derived from the alveolar epithelium. In some alveoli and in the smallest air-tubes the cell mass is so dense that individual elements can only be seen with dilliculty, but they appear to be identical with the cells just described. The process seems to be accompanied with very little inflammation. The desquamation and proliferation goes on in the alveoli and smallest air-tubes until they are occluded by the casts described. Of the 40 animals of the same herd, 17 were found with collapse (Nos. 1, 7, 8, 12, 13, IG, 18, 21, 23, 24, 28, 32, 34, 35, 41, 44, 4G), an(J eight with lobular bronchopneumonia (Nos. 2, 5, 9, 14, 19, 22, 30, 37 ; see also Nos. 434 and 435). ]\rorc than one half, therefore, had some defect of the lungs. Ifcmightbe questioned whether such lesions as those of broncho-pneu- monia are not due to swine plague bacteria, since they closely resemble the appearance found in many swine plague lungs. This question is eflectually disposed of by the inoculation of lung tissue into rabbits. From IG lungs IG rabbits were inoculated. Of these lungs 8 were in- volved in simple collapse; 8 in broncho-pneumonia. Of the IG rabbits 4 survived (Nos. 9, 18, 23, 4G) ; the remainder died of hog cholera (Nos. 2, 5, 12, 14, IG, 22, 28, 30, 34, 37, 44, 434). (The notes on these rabbits will be found in the autopsy notes of the swine as numbered.) Of the 4 survivors 3 had been inoculated from collapsed lung tissue, 1 from a broncho-pneumonia. It is interesting to note that of these rabbits 1 died in six days, 4 in seven days, 3 in eight days, 2 in ten days, 1 in thirteen days, and 1 in fifteen days after inoculation. Plate cultures from the corresponding bits of lung tissue showed a vari- able number of colonies almost invariably non-liquefying, and in many cases identified as hog cholera bacteria. These facts lead to the inference that in hog cholera the specific bacteria will find their way to any diseased portion of lung tissue, and there multiply to a certain extent. In one case a plate culture from a bit of normal lung tissue showed but one or two colonies, while a bit of collapsed tissue from the same lung showed a large number. There is no doubt that the slight exudate and feeble circulation in collapse and the abundant partly cellular, partly mucus or fibrinous exudate into the air spaces in broncho-pneumonia furnish a favorable nidus for jiathogenic bacteria. These may have been carried there by the blood or they may have been introduced from without. If the latter supposition l)rove true, and there are no valid objections to it, diseased lungs in hog cholera may not only become the means of disseminating the dis- ease through the mucus and expired air, but they may become the chan- nel, the weak spot, through which the virus enters the organism. To elucidate this question, if possible, the following instructive ex- periment was made : Two pigs (Nos. 4G0 and 4G1), about ten weeks old, received each into 56 the right iuug, December 21, 3 cubic centimeters of a beef-infusion pep- tone culture two days old, inoculated from a single colony growing in a roll culture. This had been made from a bit of spleen tissue from No. 40 of the outbreak described iu the preceding pages. There were about fifty colonies in the tube, all alike. To test the culture, a rabbit received at the same tiaie one ninth cubic centimeter snbcutaneously in the thigh. It died in five days. The spleen was much enlarged, blackish, friable, and contained hog cholera bacteria. A roll culture contained numerous colonies after two days. The liver contained no centers of coagulation necrosis, as the animal had succumbed too quickly. Ko. 400 became very weak in its hind limbs in less than a week; res- pirations short and quick; bowels relaxed. It was found dead on the ninth day. Superficial inguinal glands normal. Petecchiaeiu the slight deposit of fatty tissue beneath peritoneum of abdominal muscles. Spleen about 12 inches long, IJ inches wide, and three-fourths inch thick at the hilus, blackish, friable. A few petecchijie on cortex of left kidney. One cyst, the size of a large pea, In medulla. A large number of small hemorrhages iu connective tissue around pelvis of right kidney ; five small urinary cysts not showing on surface. Glands in lesser omentum eidarged, hemorrhagic throughout. In crecum and colon an almost continuous yellow sheet of superficial necrosis, about 1 millimeter thick, covering the mucosa. In lower colon it breaks up into isolated patches, simulating ulcers. In microscopic sections this layer is found to consist of necrosed epithelium intermixed with some round cells. On Peyer's patches iu lower ileum a yellow, soft deposit rests^ which is not adherent and might be mistaken for chyle. Lobes of right lung glued together aud to pericardium. Pleura thickened generally ; serum very slight iu amount, blood stained. On lobes of left lung, which are also glued together,. aud on right lung, tliere is a very slight deposit, about one-half millimeter thick, in the form of a net work. The pleuritis and exudate is most marked ou the most dependent por- tions of the lungs. Cavity of pericardium normal. Lung tissue not hepatized anywhere; trachea and bronchi contain a small quantity of reddish fluid. Bronchial glands and those along i^osteiior aorta hem- orrhagic throughout. Cultures from pleural cavities, as well as. those from spleen, contain only hog cholera bacteria. As shown in roll cul- tures they were very numerous iu the latter organ. While No. 400 presented such a well-marked case, No. 401, although presenting at first the same symptoms, slowly recovered. The differ- ence may have been due to the fact that with No. 400 a G-inch needle was used, while with No. 401 one only 3 inches long. In the latter case the chances for the passage of bacteria into the lung tissue and thence into the intestines were much poorer. On July 31, over seven months after inoculation, No. 401 was found dead. It had continued well and thrifty, and no more attention had been paid to it. Only the lungs and the liver were brought to the lab- 57 oratory, since all the other organs, including the digestive tract, were rei)orted normal, exce])tiiig the kidneys, which were said to be highly congested. Lungs, bat slightly colhipsed, dark red. Cei)halic and ventral lobes of boili hings and tlie nzygos lobe solid to the touch, f a grayish red color, with tortuous injected vessels under the pleura. On section, the tissue cuts like cold meat. Color grayish to (hirk red. The cut ends of bronchi show plugs of a glairy mucus. The marginal i)oition of the lobe is grayish, homogeneous, very dense. Towards the center of tiie lobes the tissue is nu)re reddish, infiltration not so dense, and speckled with small masses (one-half millimeter across) of a yellowish-white, homogeneous, cheesy matter. On the border of the right cei)lialie lobe an encysted mass, clieesy, yellowish, gritty to the knife, evidently the result of the inoculation. There were reported adhesions of the dis- eased lobes to chest wall, indicative of pleuritis. Bronchial glands slightly larger than walnuts, of a uniform grayish by individual animals, and although the disease is equally fatal in the end, the course may be somewhat different and the lesions less extensive. At the same time the bacte- ria may elude observation. They may remain more or less localized, owing to the reactive power of the organism, which destroys those that have entered the internal oigans. To those who would give up the search for hog cholera bacilli after a few unsuccessful attempts to find them, we would reccommend the perusal of the following three cases, after having reviewed the epizootic just described: Hog cholera prevailed more or less in Montgomery County, Mary- land, during the latter weeks of September and the early part of 0(;- tober, 1888. October 17 Mr. H lost about 22 out of a herd of 55 to <50 swine during the past four weeks. Of those now scattered in a large held 2 a])[)ear ill ; 1, a small black shoat, is killed by cutting its throat and examined. The superficial inguinal glands are very much enlarged, the surface mottled, dark red. The spleen large, but pale and rather firm. The liver shows signs of invasion of the sclerostoma pingiiicoJu. The lymphatic glands i\i lesser curvature of stomach are very large ; cortex completely hemorrhagic. The left lung normal ; the principal lobe of the right lung has in it a mass of tissue involved in broncho pneumonia, extending obliquely from the free border to near the dorsal region, about 1 inch thick; the lymphatics along the dorsal aorta are likewise hemorrhagic; the stomach tilled with food ; small intestines contain a number of attached cchmorhynchi; the large intestines distended with semi-i^'olid fecal mat- ter; the mucosa in general is normal, but in the caecum are two ulcers about three eighths inch across, round, slightly elevated, with center black and periphery yellow; beneath the superficial slough is a whitish, firm, new growth, extending to the muscular coat in the center of the ulcer. The spleen and the right lung were taken to the laboratory. From the former cultures were made on agar, in gelatine and beef infusion, by adding bits of spleen tissue as large as i)eas. In no tube did any development take place. A rabbit inoculated by tearing up a piece of hepatized lung tissue in sterile beef in fusion and injecting the turbid liquid subcutaneously remained well. 60 Several miles from the first farm we came upon a herd of young pigs which were just showing signs of disease, althougli none had been lost. One of them, with unsteady gair, which hid in the litter under a shed and returned to it when driven away, was killed by bleeding from the vessels of the neck. The lungs were without a sign of disease. Spleen enormously enlarged and gorged with blood. The lymphatic glands of groin and about stomach very large but rather pale, and oedematous on section. Stomach filled with food. Large intestines overdistended with very dry, hard feces, somewhat softer near caecum ; in the latter only one ulcer and this on the valve, about one-fourth inch across and of the same nature as the one found in the preceding case. A portion of the spleen of this animal was taken to the laboratory and cultures made, as in the previous case, with bits of spleen, AH cultures remained permanently sterile. Several miles from the latter place we found the disease on a farm situated on a hill. The swine were allowed to go a considerable dis- tance down the slope to a marshy stream. The owner had lost or 8 out of a herd of 20 to 25 within six weeks. A few were evidently ill, but none were killed, as a dead one was found. It had probably died during the night. The buzzards had consumed nearly all the intes- tines through a small hole near the pubis. Putrefaction had already set in. Spleen enlarged, slightly congested. In the small portion of the large intestine, which still remained, an ulcer was found three- eighths inch across. The glands of lesser omentum with hemorrhagic cortex. The stomach contains a small quantity of bile stained lluid. Both lungs glued to chest wall by coagulated fibrin from blood extra- vasation. Left lung contains about ten to fifteen hemorrhagic foci, visible under pleura, one-fourth to one half inch across. The principal lobe of right lung solid, granular, involved in broncho-pneumonia. The hepatized lobe was discolored by recent and extensive blood extravasa- tion. A gelatinous deposit under sternum resting on pericardium. The semi-decomposed condition of the animal i)revented a mor.' careful examination. Portions of the spleen and hei)atized lung tissue were taken for examination. While the spleen of the two preceding cases showed no indications of bacterial life on cover-glass i)reparations, the s[)leenof this ease con- tained a considerable number of bacteria resembling hog cholera bacilli very closelj". On gelatine they grew differently from the latter, and the cultures emitted a slightly offensive odor. In liquids they were actively motile. They were putrefactive bacteria, without effect upon two rabbits inoculated with large quantities of the cultures. A rabbit inoculated with the diseased lung tissue remained well. The latter on closer examination had a texture as granular as the roe of fishes, the granules being inspissated cell masses in the alveoli and air tabes. At least four different kinds of bacteria were present in large numbers. The absence of bacteria from the spleens of Nos. I and 2 is in har- mony with the results obtained in other infectious maladies when ani- mals are killed in the early stages or during the height of the disease. It is only in the last stages that the bacteria become most numerous and appear in sufficient numbers in the internal organs to be easily detected. In the third case, death was very likedy brought on by pulmonary hemor- rhage not infrequently found in hog cholera. The specific bacilli pro- duced at first the ulcers, and were either working their wa^' slowly into tlie, internal organs or else were being destroyed in the ulcer itself. 61 The latter termination would signify recovery; the former death. These ulcers might be aptly compared to the malignant pustule in man, in which the virus remains at first localized but may spread throughout the system after a time. The presence of numerous ulcers in swine in the first epizootic is to be regarded as a multiple infection, while in tlie three cases just cited the infection was limited to a few foci or but one. The ulcers would no doubt have revealed the virus, but ouri^revious experience with spleens of diseased swine made it seem unnecessary to study the ulcer itself. As regards the lung disease of the third case, notliing positive can be said. It resembles most closely chronic swine plague. The germ of this dis<'ase was not present, however, as shown by the rabbit inoculation. Buzzards may carry the disease from one place to another. When the dead animals are at all exposed to view they are immediately at- tacked. Whether hog cholera bacteria are entirely destroyed in the digestive tract of the birds can not be said, but there is nothing in the range of our knowledge of bacteria which will exclude the probability that the bacteria are not all destroyed during the process of digestion, and that they may be distrilmted by these birds from place to place in the discharges. THE CAUSATION OR ETIOLOGY OE HOG CHOLERA. The suspiclou eiitertajiied by those engaged in the study of diseases of mau aud the lower animals that infectious or communicable diseases are due to living organisms ot the lowest order, capable of rapid multi- plication by the process of fission and spore-formation, has been trans- formed into conviction during the past ten years. A considerable num- ber of the most common, most dreaded diseases have been proved to be caused by exceedingly minute, plant like organisms known under tlie general name of bacteria. Among animals the microorganisms causing anthrax, black quarter, tuberculosis, glanders, strangles, infec- tious pneumonia in horses and swine, and roiujet in swine have been very thoroughly demonstrated. The opinion has been steadily gaining ground that in order to control infectious diseases we must learn their causes and the life history of the pathogenic bacterium found in each disease. These will suggest to us the measures that are most likely to prove successful in combating such maladies. Moreover, it is pretty well accepted to day that the prevention of infectious diseases is the main thing to be arrived at in our studies, and that their treatment when they have ouco obtained a foothold is at best tentative and rarely successful. This is especially true of the lower animals. They cannot be treated with the same care which is accorded to human beings at- tacked by infectious diseases, They are (in some diseases at least) always scattering the living virus and thereby endangering those still free from disease. In the investigation of swine epizootics these facts have been care- fully borne in mind, so that most attention has been paid, first, to the life history or biology of the micro-organism 5 second, to disinfectants as de^troyer^)of the specific bacteria; and third, to the various methods of preventive inoculation. THE BACILLUS* OF HOG CHOLERA. During the past three years the number of swine affected with this disease which have been examined is about 500. About three-fourths * The term bacterium, implying a form genus between micrococcus aud bacillus, has been almost wholly given up by bacteriologists, and all those forms classed under bacteria have been thrown together under the genus bacillus. This change is un- fortunate for several reasons, inasmuch as many species were best classed under the genus bacterium. This latter term, which was applied to hog cholera microbes in the reports of 18d5-'c6=^'87, is iiow relnctoutly given up for the sake of uniformity. G'J 64 of tliis iiiuuber died at the experimental station of the bureau. The remainder came from outbreaks of the disease within 2 or 3 miles of the Station. Besides these, a small number of animals were examined in some of the Western States. From perhaps 400 the same microbe was obtained, there being practically no diflerence between the pathogenic microbes obtained from all the outbreaks thus far investigated. Of the internal organs the spleen contains the largest number of bacteria, and in acute hemorrhagic cases they are sufficiently numerous to be detected on cover-glass preparations. A minute bit of spleen pulp is rubbed on a cover glass, dried and heated according to the ac- cepted methods, and then stained for a few minutes in an aqueous so- lution of methyl violet. The bacteria then appear as elongated ovals or short rods with rounded ends, chiefly in pairs. When the staining has been very brief only the periphery of the rod is deeply stained, the central portion being pale and simulating the ai)})earance of an endo- spore. When the period of staining is prolonged to half hour or more, the rod may become uniformly stained. Bacteria thus dried on a coverglass and mounted in balsam measure from 1.2 tol.5, occasionally 1.8 micro-millimeters (.OOUOo-.OOOOG iiicli) in length, and about .G micro-millimeter {. 000024 inch) in breadth. In sections of the s[)leen from acute hemorrhagic cases the bacilli may be found in considerable numbers. Sections were hardened in al- cohol, cut dry, and subsequently stained with aniline water meth.yl violet. They were in some cases decolorized in 1 per cent, acetic acid. The bacilli then appear as short, plump rods, uith ends rounded otf; sometimes they are short enough to deserve the name of ovals. The periphery is more deeply stained than the central body of the rod. They measure on the average 1.5 micro-millimeters. In such sections the bacteria appear in small masses in the capillary spaces of the spleen -pulp, rarely among the cells of the malpighian corpuscles (Plate X, tig. 2). The masses appear more or less star-shaped. The bacilli are crowded together in the center : from this, linear groups ra- diate inio the cai)illary network. Such masses may be 8 to 10 micro- millimeters in diameter. They are fairly numerous in spleens from acute cases. That the size of these colonies is not due to postmortem nuiltiplicatiou is shown by the fact that the largest and most numerous colonies were found in the spleen of an acute case which was examined within two hours after death, in the month of November. In sections of ulcers hog cholera bacilli have been searched for, but the examination of a large number of ulcers showed that no positive results could be obtained. Different ulcers showed different bacteria, sometimes large colonies of micrococci, sometimes groups of large ba- cilli, following the course of the blood-vessels in the embryonic tissue under the slough. These no doubt found their way in from the super- ficial slough which seemed to be made up almost entirely of bacteria. Moreover, hog cholera bacilli closely reseujble ijiany putrefiictive forms, G5 so that even if they could be readily seen nothing- but a good diflfer- eutial stain would enable us to recognize tbem. That they are present, however, may be demonstrated by inocuhiting mice or rabbits with bits of the ulcer. A small number of mice may succumb to malignant oedema. The rest will die of hog cholera. In rabbits the local effect of such inoculation is usually quite severe, owing to the putrefactive bacteria introduced at the same time. Stainingof hog cholera bacteria, — On cover-glass preparations they are easil^^ brought into view by a few minutes' contact with water}' solu- tions of the ordinary aniline colors, such as methyl violet, fuchsin and methylene blue. Decolorizing agents, such as acetic acid, one-half to 1 per cent, must be used carefully lest the color disappear from the bacilli also. When stronger dyes, such as alkaline methylene blue orani- ]ine water fuchsin, are employed, the bacilli are decolorized with greater difficulty. Watery solutions should therefore be employed only for cover-glass preparations where decolorizing is unnecessary-. Forsections it is well to harden tissues in alcohol. The sections may be stained with Lofder's alkaline methylene blue or with aniline water methyl violet or fuchsin for from one-half to one hour. After a a few seconds' contact with a 1 per cent, solution of acetic acid they are washed in water, then passed through alcohol, turpentine, or xylol or cedar oil, and mounted in xylol balsam. Xo stain which differentiates these bacilli very sharply from others has been found. They are decolorized when the method of Gram is employed. Distribution of bacteria in the body.-^This can be best determined by the delicate method of cultivation. In acute cases the spleen contains the largest number. In coverglass preparations of spleen pulp there may be. four or five in every field of the microscope. In general, the liver contains almost as many bacteria as the spleen. The lungs, lymphatic glauds, and kidneys may also contain them in moderate number. They are fewest in blood from the heart (right ventricle). In slow, chronic cases, characterized by slight ulceration of the large intestine, the number of bacteria in the internal organs is very small. From the spleen of such cases cultures are made fertile only by using bits of tissue as large as split peas. Whcu it is of importance to make a diagnosis from a chronic case it might be well to adopt the method suggested byFriinkeland Simmonds for typhoid fever. They wrapped the spleen in cloths wet with a solu- tion of mercuric chloride and placed it in a warm room for twenty-four hours. The bacilli of ty[)hoid, capable of multiplying in the organs after death when the temperature is not too low, became suflScieutly numerous to be readily detected in sections. The same may be said of hog cholera bacilli. It must, however, be borne in mind that in chronic cases other bacteria may have gained entrance into the body and appear in the spleen. These, multii)lying at the same time, may give rise to erroneous inter[)retations. 15G12 II c 5 66 When the destruction of the mucous membrane in the large intestine is extensive, bacteria of various kinds may be found in the peritoneal cavity. The serum collected often contains several varieties of organ- isms, and when sections are made of the walls of the peritoneal cavity micrococci and bacilli are seen resting in a thin layer upon the perito- neum. Sometimes the pleural fluid, and still more rarely the pericar- dial fluid, may give rise to cultures of micrococci. These resemble the micrococci, causing suppuration in man {stajphiilococci) in their appear- ance and mode of growth in gelatine. The presence of anaerobic bacilli in spleen and liver has already been dwelt upon. The presence of bac- teria in the peritoneal cavity is easil}' explained by their passage through the ulcers in the intestines. It is a fact worthy of note that only very rarely bacteria other than those causing the disease were encountered in the spleen and the circulation. Perhaps those causes or agents which destroy bacteria are less active in the serous cavities than in the blood and spleen. The various complications of chronic ulceration already mentioned, such as peritonitis, pleuritis, and pericarditis, are without doubt due to this secondary invasion of bacteria, which have the power to produce inflammation of serous membranes. It need not be said that in the earlier investigations, when little was known of bacterial diseases, the explanation of the presence of these microbes was very perplexing and misleading. Biology of the hog cholera bacillus. — The cultivation of bacteria in nu- trient media outside of the animal body serves two distinct purposes: (1) The diagnosis of specific forms so that they may be easily recognized, and (2) the study of their biology or life history. a. Diagnostic characters. — Hog cholera bacilli are not readily dis- tinguished from a large number of other bacteria found in surface waters and in the superficial layers of the soil, either in their form or in their manner of growth in culture tubes. The more minor difteren- tial characters we can therefore obtain, the more certain our diagnosis will be. For this end the hog cholera bacillus was cultivated in as many media as were available. If a bit of spleen pul[) from swine which have succumbed to hog cholera be thoroughly shaken up in a 10 per cent, beef infusion peptone gelatine, liquefied by a gentle heat, and the whole poured upon a sterile glass plate protected from the dust by a bell glass and allowed to con- geal, colonies of hog cholera bacilli will a])pear within forty-eight hours as mere specks to the naked eye. Examined under a low power they are spherical, with sharply defined border. The disk of the sphere is homogeneous without any concentric markings, and of a brownish color. This description applies to colonies beneath the surface of the gelatine layer. Colonies which grow on the surface soon spread out into thin pearly layers several times the size of the deep colonies, and roundish or irregularly polj^gonal in outline. Besides the deep spherical and the flat surface colouies there is oc- casionally a third form present. This is a ver^- faint cloud like colon^y 67 growiug between the glass plate and the gelatine, si)reacliug as a very thin layer laterally and attaining the dimensions of a snrface colony. Many snch colonies have spherical prolongations upwards into the gela- tine layer so as to assume the form of a lid with a knob like handle at- tached to its center. It is very probable that the colony begins as a sphere in the gelatine layer near its lower surface. As soon as it touches the glass, by virtue of its enlargement, spherically, it spreads out into the attenuated, cloud-like layer. Such colonies are rare, ex- cepting in so-called line cultures made by drawing a platinum wireacross the gelatine layer before it has congealed. Perhaps the best device for studying the growth of such colonies is the Esmarch roll culture.* The gelatine, coating the inside of the test tube, is protected from contamination and desiccation for a long tinie. The colonies have thus the opportunity of expanding to their utmost capacity. In a roll culture ten days old, for example, the deep colonies W'Cre about one half millimeter in diameter, perfectly spherical, the disk homogeneous, yellowish white, when viewed with a hand lens. Under a 1-inch objective it appeared reddish brown, with no markings. The surface colonies in the same tube were about eight times as large, i. e., 4 millimeters across. They presented centrally an opaque white patch or nucleus, outside of this a more translucent zone, beyond this another opaque zone, and lastly a limiting transUicent border. The colonies were irregularly i)olygonal in outline. The alternation of thin and thick zones was very likely due to the variation in .temperature to which gelatine cultures were exi)osed in a badly heati d laboratory, for they are by no means always present. (Plate XI, fig. 2.) Tube cultures, made by piercing the gelatine in a test tube with a l)latinum wire previously forced into the spleen, show minute yellowish- white spheres in the track of the wire in forty-eight hours. These rarely exceed one half millimeter even after several weeks. The snrface growth spreads from the place of inoculafiou as a thin pearly layer of variable thickness, ev( ntually becoming 4 to G millimeters in diameter; under especially favorable conditions of temperature, etc., it may be- come still larger. ^Vhen the inoculated bacteria are very numerous the growth beneath the surface appears as a solid yellowish-white track, in which the colonies have become fused together. The gelatine is at no time liipietied. The bacilli grow somewhat larger in gelatine than in the body of diseased animals. Occasionally filaments of considerable length are met with, and in general irregular, involution forms are not " These roll cultiu-es are made as follows: The gelatine, luiueticd l)y j^entle heat in the tube iu which it was sterilized, is inoculated with the tissue, Idood, urine, or any lir|uid containing bacferia, and carefully stirred up. A second culture uuiy be made from the first by transferring from it with a platinum loop some of the liquid gela- tine. This is done when the number of bacteria in the lirst tube may be too numer- ous. A rubber cap is litted over the month of the tube after replacing and trimming the cotton- wool plug, and the tube i)laced horizontally iu ice water and rolled about its long axis until tlie inside of the tube is coated witli a uniform layer of congealed gelatine. The tube may also be rolled on a smooth block of ice, a method which I first saw in the Pathological Laboratory of Johns Hopkins University, and which is very useful when rubber caps are wanting, or when it is desirable to licep the phig free from gelatine. 68 uncommon. When a bit of spleen tissue is rubbed upon iin inclined surface of agar agar in a culture tube, isolated colonies make their ap- pearance within twenty-four hours as circular, grayish-white, semi- translucent, very flat cones 1 to 2 millimeters across. When the ba- cilli are very numerous a slight prick of the spleen pulp with a platinum wire is sufficient. Otherwise the too numerous colonies will coalesce into a grayish, shining, semi-opaque layer of scarcely perceptible thick- ness. Its appearance on a^rtrcan not be distinguislied from the growth of typhoid bacilli and a number of saprophytic bacteria. On blood serum the growth a^ipears as a very thin, grayish, translucent layer. In bouillon, either with or without peptone, the bacilli grow rapidly enough at 80° to 95° F. to produce a slight opalescence within twenty-four hours. This does not increase in density subsequently. There is no membrane formed on the surface of the liquid. When standing undisturbed for one or two weeks, a white ring-like deposit of bacteria frequently forms around the tube at the surface of the culture liquid. There is only a very slight deposit formed, showing that multiplication in liquid media comes to an end within a few days. The length of the bacilli in bouillon is about .9 micromillimeter, their width .4 to .5 micromillimeter, therefore somewhat smaller than in the spleen. When examined in a drop of bouillon suspended from the under surface of a cover-glass in a " cell," the bacteria are seen to be motile. Taken from cultures one or two days old thej^ execute very ac- tive spontaneous movements. Their movement is one of rotation as well as translation. They quite invariably occur in pairs, and the movement of rotation is about their point of union as an axis. The pairs of bacilli as they shoot across the field have thus an oscillating motion at the same time. The bacilli do not come to rest at all, but swarm about very rapidly until the liquid is dried up. Though this motility is most marked in recent cultures, it may still be seen at the end of one or two weeks in most liquid cultures. The same active motion is observed in bacilli taken directly from the animal, such as the spleen of rabbits, which have succumbed to inocu- lation. If a bit of spleen tissue be rubbed in a drop of sterile water on a cover-glass and the whole examined as a hanging drop, in one or two minutes the bacilli become as active as in cultures. Growth on boiled potato, when at 95'° F., appears as a faint straw- colored deposit within tw^enty-four hours after iuoclution. At 20° to 25° C, it appears one or two days later. It slowly spreads in all direc- tions as a layer of perceptible thickness. The color changes to a dark brick red, or may remain whitish. In general the growth is darker the more rapidly the potato dries up. The growth is also restricted by drying. In some sultures it has covered almost the entire cut surface of the potato. In others it re- mained as a broad band over the line of inoculation. The bacilli multi- ply very abundantly in milk without producing any alteration visible to the naked eye. G9 Tlio diagnosis of hog cholera bacilli may therefore be made by taking together the following morphological and biological characters : (1) Short bacilli with rounded ends, or ovals, readily stained in aqueous solutions of aniline dyes. (2) Growth at GS^toSCP F., on gelatine, with- out producing liquefaction. (3) A rather feeble growth in beef infusion coupled with active spontaneous movements. (4) Growth on t'lc cut surface of boiled potato at ordinary temperature as well as in the incu- bator, (o) Active multiplication in milii without any macroscopic changes. (G) Growth in racuo. (7) Absence of any odor arising from the cultures. (8) Fatal effect on rabbits, guinea-pigs, and mice when inoculated. This will be discussed later on. These characters are emphasized, since we have several times found bacteria in the internal organs of swine which may have many points in common with hog cholera bacilli; especially as regards their form, motility, and growth in gelatine. In fact in w;is quite impossible to decide until inoculations upon animals were m;ule. The absence of pathogenic power was thus made the chief critei ion. {!)) Other plujsiolooical characters. —Though alkaline media are as a rule most favorable for bacterial multiplication, yet there is a slight devel- opment in media containing a small amount of acid, such as Liebig's meat extract. A feeble development was observed in sterilized hny infusion. The temperature range of the active multiplication of hog cholera bacteria lies between (Joo aiid 104c F,, being most favorable between 85° and lOOo F. Hog cholera bacilli, though they seem to develop best in presence of oxygen, are capable of growing in what is practically a vacuum, *. e., they are facultative anaerobic organisms. Comparative experiments made with such obligatory aerobic organisms as bacillus subtilis deter- mined that while the latter shows no trace of growth in tubes from which the air has been removed, hog cholera bacilli grow quite as freely as in presence of air. When the latter are shaken up in liquid gelatine in test tubes and the gelatine rapidly congealed the colonies that appear throughout the gelatine show no difference in size, whether near the surface where air can penetrate or near the bottom of the tube. THE DIAGNOSIS OF IIOCI CHOLERA BY MEANS OF INOCULATION. The inoculation of small animals in the study of infectious diseases has been of the utmost importance from a diagnostic stund-point. Fre- quently bacteria which are nearly identical in form, size, and many biological characters, can only be distinguished from one another by their effect upon smaller animals. This is especially true of hog chol- era, since the specific bacillus closely resembles many forms found in decomposing liquids. In the following pages, therefore, a careful ex- position of hog cholera as manifested in small animals will be made to facilitate the diasrnosis of this disease. During the course of these in- 70 vestigatious rabbits have been fouud best for this purpose, altliongh ordinary bouse mice and guinea-pigs will answer almost as well. If a bit of spleen tissue from a case of bog cbolera be inserted under tbe skin of the tbigb, or simply rubbed upon a sligbt abrasion made on the inner surface of tbe ear, or if tbe bacilli from pure cultures be used, tbe disease will be induced. The rabbit will succumb within a period after inoculation varying from five to fourteen days (very rarely longer), depending upon the number of bacteria introduced. The period of incubation, during which the animal shows no symptoms, varies from three to five days before death. At this time the tempera- ture rises from the normal (102.oO-103.5o F., according to the age of the animal), to 107° or 108^ F.. and remains at that point unt'l shortly before death, when, if examined in time, a fall is observed. The height of the fever is accompanied by loss of appetite and a tendency to sit perfectly quiet. The disease thus induces in the rabbit a typical continuous fever in- variably ending in death. By way of illustration, the temperatures of a few cases are here reproduced : Kabbit inoculated June 18, with^ cubic centimeter culture liquid; weight, 2^ pounds ; temperature, 102.5° F. ; at end of first day, 102.7 ; of second day, 104.G; of third day, 105; of fourth day, 108; of fifth day, 10G.4: ; dead on sixth day. Eabbit inoculated June 20, with infected soil, one and one-half months old; temperature on fifth day, 10.'i.4 ; on seventh day, 103.8; on eighth day, 103.8; on tenth day, 107.fi; on eleventli day, 107.4; dead on twelfth day. Rabbit inoculated June 28, with i cubic centimeter of culture liquid ; weight, 2yg pounds; temperature, 103.7° F. ; end of first day, 103.3; of second day, 105.5; of fourth day, 107.8; found dead on seventii day. The lesions produced are very constant and characteristic. At the point of inoculation there is a slight infiltration of the subcutis and fascia, and occasionally a slight superficial necrosis of the muscular tis- sue. The spleen is very large, perhaps t hree to five times its normal size. The liver presents on its surface yellowish white patches which corre- spond to one or more lobules which have undergone coagulation necro- sis. These patches vary greatly in number but are rarely absent, pro- vided the animal lived long enough to permit their formation, i. e., not less than seven to eight days after inoculation. This necrosis appears chiefly in lobules near the surface, although occasionally the entire tissue is involved. In some livers the necrosis is complete so far as the lobule is concerned. In others it is restricted to the peripheral or portal zone of the lobule, in which case a large patch of lobules usually undergo the same change. There can be no doubt that they represent dift'erent stages in the process which seems to begin in the portal area. When sections are examined under the mi- croscope the liver-cells show as unstained nmsses without nuclei. There 71 is a remarkable absence of leucocyte infjltration aroniul the necrosed tissue. The bacilli are very well brought out in such tissues after thor- ough hardening in alcohol, by staining over night in aniline water methyl violet (tubercle stain), and decolorizing slightly in A to 1 per cent, of acetic acid. The deep bine bacilli a])pear in dense masses, chiefly in the capillaries along the edge of the necrosed area. The ne- crosis is most probably due to the plugging of the different vessels, thus cutting off the blood supply. The enlargement of the spleen and the necrosis in the liver are the two important characters of the inoculation disease. In a moderate number the intestinal tract is found diseased. The submucosa of the duodenum near the pylorus is dotted with ecchymoses, which may fuse into a single hemorrhagic patch. Besides this the submucosa of the large intestine 2 to 3 inches from the rectum, i.e., the straight portion merging into the rectum, may be iu the same condition. Sometimes the nuicosa is beset with minute bulging ha'matomata. These intestinal lesions are due to the discharge of bacilli from the necrotic foci in the liver into the bile ducts aud thence into the duodenum. The lesions in the large intestines may be influenced by the more or less prolonged stay of the feces before final discharge. In some cases when the disease has lasted from ten to thirteen days there is a peculiar exudate iu the large intestine, which may be drawn out of the anus in the form of bands or cylindrical masses ] or 2 feet long, consisting of a translucent, elastic, whitish material, finely fibrd lated when examined under a high power. The duodenum may be dis- tended with a straw-colored semi-gelatinous mass. Hemorrhagic lesions may also be present. It seems very probable that the exudate is the result of a fibrinous or croupous inflammation of the large intestine due to the presence of hog cholera bacilli. The lungs are occasionally the seat of hemorrhages. The kidneys contain more blood than usual, but hemorrhages are absent. Hog chol era bacilli are obtained by cultivation from uearl\' all the internal organs. They are usually so abundant in spleen aud liver as to be detected readily iu cover-glass preparations. The following experiment shows how few bacteria are required to pro- duce the divsease : Rabbit Ko.^;i^-l-itV Remarks. 17 1 oBii'jjBis c. c Dead on sixth day. 18 iBBOBij c. c Dead on ninth day. 19 1 4500OB5 c. c Dead on eighteenth day. 20 I jgnJsiyTj c. c Dead on eighth day. The beef-infusion culture was diluted so that one-quarter of a cubic centimeter of the liquid contained the equivalent given in the table. It s probable that ^o. 19 took the disease from No. 20, penned with it. The latter had ecchymoses iu the duodenum, indicating that the bacilli 72 bad escaped into the intestinal canal and were being discharged with the feces. The time of death of Xo. 1.9 suggests this view. A very small number of bacilli, therefore, are sufticient to produce in rabbits an infectious fever, or septiciiemia. The characteristic action of hog cholera bacteria on the mucous mem- brane is well illustrated by feeding cultures to rabbits: kSeptemljer 11, 1888. — Two rabbits were starved for one day and then fed hog cholera bacilli from an agar culture on clover. This was readily consumed. One rabbit was found dead on the sixth day. Agglutination of blad der to cajcum ; serosa of stomach reddened. Ileum about G inches from valve invaginated for 2 to 3 inches. Spleen congested, slightly en- larged. Liver and kidneys engorged. Large numbers of hog cholera bai.'illi in spleen, as tested by the microscope and cultivation on gela- tine. The other rabbit died in thirteen days. Spleen very large, con- gested ; coagulation necrosis in liver. Lungs contained several dark- led hepatized areas. Severe lesions were found in the large intestine. The mucous membrane of lower colon and rectum were dotted with small bulging hemorrhages, and the tube contained a cylindrical mass of a material resembling colorless gelatine, partially softened in water and very elastic (tibrin?). Tiie duodenum was distended with a pale yellowish translucent semi-gelatinous mass. Hog cholera bacilli as above. At the same time two other rabbits were starved for a da>' and then 5 cubic centimeters of a liquid culture was added to 20 cubic centime- ters wati-r and given them to drink. One rabbit died in ten days. The lesions were the same as those in the rabbit just described, with this exception, that there was no coagulation necrosis in the liver. The other rabbit did not take the disease. It is quite likely that it may not have taken much of the water. When rabbits are not easily procurable the ordinary house mice may be used. They usually appear quite well and active after inoculation until some morning they are found dead. The period of the disease is the same as that for rabbits. The spleeu is very large; the liver con- tains many centers of necrosis. Mice have been frequently fed both with pure liquid cultures and with spleeu pulp containing hog cholera bacilli. They invariably take the disease and die within seven or eight days after the first feeding, with lesions the same as those observed in mice inoculated subcutaneously. Two mice were peculiarly affected the day after eating some spleen pulp. They were scarcely able to move. Their limbs sprawled, and on being taken out of the jars they remained in this position unable to escape. They died subsequently of true in- fection. The symtoms recorded were due very likely to the absorption of the ptomaine produced hj the bacteria in the digestive tract. There is a remarkable regularity in the length of the disease in mice. Those inoculated at the same time and with approximately the same dose usually die not more than a half a day apart; they appear lively up to the night during which they die. In one case four mice, inoculated at the same time, all died in the night of the seventh day, though they appeared well the day previous. 73 The followiug- experimeut is wortb}' of record as iudicatiug the effect of hog cholera virus on mice that survived infection : October 28, 1S8S. — Two mice were fed witli bits of liver and kidney tissue from mice whicli liad succumbed to inoculation with hog cholera cultures. The material fed had been kept in the refrigerator Hoc nearly four weeks in salt solution. Before feeding it was thoroughly mixed with bread crumbs and placed in the mouse cage. Both mice survived the feetliug and were active December 1, over one mouth after feeding. One was thereupon killed with chloroform and examined. The spleen was very much enlarged, not congested abnormally. On the ventral aspect of the liver a whitish patch where diaphragm was adherent. Under the patch a large abscess. This, was without doubt the site of extensive coagulation necrosis, which was now broken down. The second mouse was killed December 19. over seven weeks after being fed. The spleen was likewise very large, the liver intact, but there were live abscesses in the left kidney, with adhesions to .surround- ing structures. On section one abscess was wedge-shaped, tlie apex being at the pelvis; the whole only partlj^ softened. These also were the result of coagulation necrosis. We have here a striking illustration of the mainly mechanical injur,y doue by hog cholera bacilli. The effect of hog cholera bacilli on guinea-pigs differs but little from that exerted on rabbits and mice. The duration of the disease and the lesions are the same. There seems to be a somewhat greater tolerance in guinea-pigs, although the small number used does not justify any decided statement. Pigeons arc also susceptible to this disease, but by no means to the degree witnessed in the animals just mentioned. It requires about three-fourths of a cubic centimeter of an ordinar^^ beef infusion pep- tone culture to produce a fatal result (/. e., about 150,000 to 3,000,000 times the dose necessary to destroy rabbits). The birds frequently died within twenty-four hours after the injection, which was usually made under the skin over the pectorals on one or both sides. The pectoral after death is x)artly or wholly discolored, and has a par- boiled appearance. The injected bacteria are present in the heart's blood and in other organs, notably the liver. If the dose is smaller than three-fourths of a cubic centimeter, the bird may survive after a week or two of pronounced illness. A large sequestrum forms in the pectoral muscle, which is gradually absorbed. Occasionally the birds will die after a week of illness manifested by diarrhea, ruffling of the feathers, and a quiet, somnolent attitude in a corner of the cage. Hog cholera bacilli are also present in the internal organs in such cases. Feeding cultures has no effect. Fowls have been frequently inoculated and fed with cultures without showing any signs of susceptibility. Among other animals inoculated were several white rats, one gray rat, one sheep, and a calf. lu none did the disease appear. In the sheep and calf a small abscess was found at the place of inoculation. VITALITY OF HOG CHOLERA BACILLI, AXD THEIR RESISTANCE TO VARIOLS DESTRLCTH E AGENTS. The vitality of bog cliolera bacilli in cultures remains for months nn- chauged. The following is perhaps an extreme illustration : A tube of beefs blood serum, coagulated by lieat, was inoculated with hog cholera bacilli November 28, i885. The platinum wire penetrated the blood serum and the bacteria grew as a slender i)lug in the needle- track and as a thin film on the surface. In July, 1887, more tlian one and one-half years later, a tube of beef infusion inoculated from the blood serum culture became promptly turbid, and contained the hog cholera bacilli only. Two mice inoculated subcutaueously with a few drops August 2, died Augusts and 9, respectively, with lesions characteris- tic of the disease and with the bacilli present in spleen anvl liver. The germs had not therefore lost their virulence. The blood serum had con- tracted but slightly from loss of water, there being very little evai)o- ration from the culture tubes used. Resistance of hog cholera hacieria to heat in liqnids. — A knowledge of the degree of heat necessary to destroy liog cholera bacteria is of con- siderable importance, not onlj" in its bearing upon the ap[)lication of heat as a disinfectant, but also upon the various processes that are used in the preparation of pork for consumption. Culture tubes containing about 10 cubic centimeters of beef infusion were inoculated from a culture of a certain age and then placed in a water-bath kept at the desired temperature. They were exposed for different periods of time and then removed to an incubator at 95° F. When the tubes remained clear it was inferred that the bacteria had been destroyed. A control tube was inoculated in every experiment to make sure of the vitality of the culture used. A momentary exposure to boiling water will destroy them. When the temperature of the surrounding water is 158° F. (7(P C). the in- oculated tubes remain sterile after an exposure of four to five minutes. As it takes about four minutes for the temperature of the culture liquid to reach 70° C, it is probable that a two minute^' exposure to 70° C. would be sufficient. An exposure to 130° to 138° F. (58°-59° C), is sufficient to destroy hog cholera bacteria in fifteen minutes. The same is true for bacteria taken directly from the spleen. An exposure to 130° F. (54.5° C.) will destroy them in one hour. Tubes exposed for one-quarter of an hour become turbid within twenty-four hours. Those exposed for one-half 76 and three-quarters of an hour become turbid within fort^-eight hours. This shows that most of the bacteria have beeu destroyed by such pro- longed exposure. Tubes heated for one hour remain clear. When the temperature is still more reduced, to 120^ F. (49^ C), ex- posure for a period as long as two hours is insufiicient to destroj^ them, altliough their growth may be slightly retarded. It must be remembered that these results mean that the bacteria must be actually exposed to these temperatuies for the length of time indicated. In the culture tubes employed it takes about five minutes to bring the temperature of the liquid up to 70° C, and less for lower temperatures. If, therefore, it takes longer than this for tiie heat to penetrate into meat or lard containing these bacteria, their destruction can not be regarded as certain within the time indicated above, and the exposure to the required temperature must be correspondingly lengthened. Hog cliolera bacteria in 10 cubic centimeters bouillon placed in a water-bath at — 1C0°C. (212° F.).. 70° C. (158° F.)... 58° C. (138<^F.)... 54.50 c. (ISO'^^F.). 49° C. (120° F.)... Time in which .destroyed. Immediately. 4 minutes. 15 minutes. 1 hour. Not in 2 hours. Bacteria do not so readily succumb to heat when dried and then ex- posed to dry hot air. It was found that dry heat at 80° C. (170° F.) is sufficient to destroy the bacteria when exposed in a dry state for fifteen minutes. In these experiments bacteria from cultures were rubbed on the inner side of plugged and sterilized test tubes. Gelatine was added after they had been exposed to the heat and roll cultures made. Absence of growth indicated the death of the contained bacteria. Kesistance to freezing is well illustrated in the experiments reported in the section on the vitality of hog cholera bacilli in the soil during winter. Vitality of hog clioUra bacteria in ordinary water. — The hardiness of this microbe is well illustrated by its capacity for multiplication in or- dinary drinking water. To determine this, the following experiment was made : September 8, a culture tube containing very clear Potomac drinking water* which had been sterilized several weeks previous by a tem- perature above 110° C, was inoculated with a platinum loop from a pure liquid culture of the bacillus. By mixing a given quantity of this water immediately after inoculation with gelatine, and making a plate culture of the same, it was found that the water contained about 20,240 * When drawn this water did not contain more than 100 to 200 bacteria to the cu- bic centimeter. 77 bacteria in 1. cubic centimeter. The water was kept in the laboratory, in wbicli the temperature corresponded closely ^ith that prevailing out- doors. It was examined from time to time on gelatine plates, and the number calculated for 1 cubic centimeter. The following figures give the results obtained : September 8, 2G,'-'J:0 in 1 cubic centimeter (immediately after inocula- tion). September 9, 201,<)()0 in 1 cubic centimeter. September 10, 1,290,000 in 1 cubic centimeter. September 11, too numerous on plate to be counted. September 13, 2,008,200 in 1 cubic centimeter. September 15, 1,519,500 in 1 cubic centimeter. September 17, ],.3()0,308 in 1 cubic centimeter, September 29, 83,700 in 1 cubic centimeter. October 12, 19,125 in 1 cubic centimeter. October 21, 10^880 in 1 cubic centimeter. November 18, 225 in 1 cubic centimeter. December C, a few bacteria still present, as determined b,y liquid cult- ures. January 4, 17 in 1 cubic centimeter. January 11, no growth on plates. According to another experiment the vitality lasted about two months. June 13, 18S8, 30 cubic centimeters, Potomac drinking water, sterilized in a Salmon culture tube, was inoculated with a platinum wire to whicli a minute bit from the surface growth of an aijar-agar culture adhered. Plate cultures prepared immediately after thoroughly shaking the tube, indicated that each cubic centimeter of the water contained from 1,000,000 to 2,000,000 germs. Plate culture of June 14 shows in Jg cubic centimeter of water a very large number of colonies. Roll cultures made June 22, July 3, and July 16 contain a smaller number. A roll culture of August 4 contains about 200 colonies {i. e., about 0,000 in 1 cubic centimeter). A roll culture of August 25 remains sterile. A tube of beef infusion to which about 1 cubic centimeter of the water had been added Sep- tember 15 contained a large coccus five days later; no hog cholera germs. These cultures show that the bacilli perished in about two months. The difference in the results obtained in this and the last experiment may have been due to the season of the year. That the bacilli can be kept alive in clear river water for from two to four months and perhaps longer is a fact very significant in itself. When we consider, moreover, that the added bacteria in the first experiment multiplied so that each individual was represented by ten at the end of five days, the hardiness of the bacillus is very evident. The danger from infected streams into which feces from sick animals find their way is thus proved beyond a doubt. Stagnant streams and pools are more dangerous, since the water is but slowly renewed, while in rapidly flow- ing streams the bacteria are speedily carried away. On the other hand, the latter may spread an epidemic from one place to another. 78 Besistanre to continuous drying at ordinary temperature (60° to 80° F. — A number of experiments were made to determine this point. Some of tbem are reported in full in preceding Annual Reports of the Bureau, and are therefore simpl3' summarized in this place. (1) A series of cover-glasses, upon each of which a drop from a liquid culture had been dried, were placed in bouillon at dift'erent times. No growth in bouillon after they had been dried from seven to nine days. (2) Minute bits of spleen tissue from a pig which had succumbed to hog cholera were tlried on cover-glasses. These were capable of infect ing bouillon uj) to the twenty-third day. (3) Spleen tissue dried on four cover-glasses gave rise to pure cult- ures of hog cholera bacilli after forty-nine days. (4) Hog cholera bacteria from a liquid culture one week old, dried on silk threads, were placed on a gelatine plate from time to time to ob- serve any growth. They were stilfcapable of develoi)ment after tweury- one days, when the stock of threads was exhausted. ^^5) Threads steeped in a liquid culture one day old and dried were placed on gelatine plates, as described in series 4. No colonies ap- peared on the twenty-seventh and twenty-eighth days. A few appeared later on, showing that even after thirty days a few still survived. In these series of experiments the vitality of the bacilli was not ex- hausted after forty-nine days in one series; in another it was destroyed in less than ten days. The following series of experiments, made during the i)resent year, show how very varied is the length ot time during which the bacilli remain alive when dried: June 15. — Minute bits of spleen tissue, from a rabbit whicli had died of hog cholera after inoculation with a pure culture, were rubbed on sterile cover-glasses and kept under a tlamed funnel, plugged with cotton- wool. On July 3, G, and 9 two cultures were made by dropping into each tube of beef infusion a cover-glass. All six tubes remained clear. The bacilli had thus perished within three weeks. In the following experiment hog cholera bacilli remained alive for more than four months: June S. — From an agar-agar culture, three days old, some of the abundant surface growth was placed upon sterile cover-glasses, each receiving about as much as the point of a platinum wire could hold. These were placed on a flamed glass support under a flamed and plugged glass funnel, and kept in the laboratory, the air of which was moderately dry. Two cover- glasses droi)ped into beef infusion pei)tone June 25. One culture remains clear, the other clouded in one day ; contained only n)o- tile hog cholera bacilli. Two covers were added to beef infusion June 20, July 0, and July 16. All six cultures became clouded and contained only hog cholera bacilli. Of two cultures made July 23 only one becomes clouded, and is a pure culture of hog cholera bacilli. Of two cultures made August 2, both become clouded with liOg cholera bacilli only. 79 Four cultures, made on August 0, 22, 30, aud September 14, became clouded with tlie same microbes, aud these alone. A tube into which a cover-glass bad been dropped September 21 remained sterile. A tube inoculated in the same way September 26, became turbid on the second day, and contained hog cholera bacilli only. A tube inoculated on Oc- tober 8 was still fertile. The stock of cover glasses had become ex- hausted. It will be seen from the above results that some of the germs were dead in one and a half and three and a half months; all the rest were capable of multiplication for four months. The prolonged vitality was no doubt due to the massing together of the germs from the OQar cul- ture, for on those cover glasses which failed to inoculate cultures, or in which the appearance of growth was retarded, the quantity of growth was smallest. The interesting question here arises whether it is the oxygen of the air which gradually destroys the bacilli, since this is more or less kept away when they are massed together, and since all pre- vious experiments with bacilli suspended in liquids have shown that the period of their vitality may average not more than two months when in a dry condition. On August 30, after having been dried for two months and twenty- two days, two mice Avere inoculated with a liquid culture obtained from one of the cover-glasses. Both died of hog cholera on September 14 and 15, respectively. The vitality of hog cholera bacilli during continuous desiccation may thus last from two weeks to more than four months. In the soil, and in nature generally, bacteria are rarely subjected to continuous drying, but to alternate wetting and drying. In order to observe the effect of such alternation, some of the same agar-agar culture used in the preceding experiment was placed in the bottom of a sterile watch glass under a funnel June 8. June 15. — About one-third cubic centimeter of sterilized distilled water added to the* watch-glass, so as to cover the dried film completely. The water was evaporated entirely next day. June 22. — Sterile water added again ; dried up next day. July 3. — Water added again aud two cultures made; both remain sterile. July G. — A liquid culture made by adding some sterile water to the dried culture mass, stirring it up aud transferring the water with a sterile pipette to a tube of beef infusion. This also remained clear. Thus bacilli from the same culture which resisted continuous drying for at least four months were destroyed in less than a mouth when a moist and a dry state alternated. This fact, so striking aud important, needed confirmation. September lij. — A considerable quantity of the surface growth from an agar-agar culture two days old was rubbed on the bottom of a sterile watch-glass covered by a plugged funnel as before. Thoroughly dry next day. September 18. — A small quantity of sterile distilled water added. This was dried up next day ; the germs had spreacl out into a thin layer. 80 September 21. — Sterile water added agaiu and a tube of beef infusion peptone inoculated with a loop from tlie liquid stirred u[>. Tube turbid with lioj;' cholera bacilli next day. September 20. — Sterile water added again. The tube of beef infusion peptone inoculated at the same time. Pure culture next day. October 1. — Tbe same process repeated ; culture contains hog cholera bacteria. October 8. — Dried bacilli wetted again with sterile water. Tbe cul- ture made from them becomes turbid; only hog cholera bacilli present. October 15. — The same i)rocess repeated; the inoculated tube be- comes turbid after forty-eight hours. October 22. — After wetting the dried growth again, it was thoroughly stirred up and several drops added to a liquid culture. This tube re- mained permanently clear. This experiment therefore confirms the other in showing that hog cholera virus is far more quickly destroyed when it is alternately mois- tened and dried than when it remains continuously dry. In both tests the germs died in one-third the time required to destroy dried virus. SOME EXPERIMENTS ON THE LENGTH OF TIME DURING WHICH HOG CHOLERA VIRUS REMAINS ALIVE IN THE SOIL. The virus of hog cholera is quite tenacious of life in spite of the fact that no spores are foruied. During the past year some preliminary experiments were made concerning the vitality of hog cholera bacteria in the soil. This becomes infected during epizootics of this disease by the discharges of the sick perhaps more thoroughly than anything else in the surroundings of the animals. Moreover, it is the most difficult to disinfect, as we have no knowledge of the depths to which the living virus may be carried by water. If it can be shown that the life of such virus in the soil is speedily destroyed, the piecantions to be taken would be quite different from those needed if it exists for a long period of time. Experiment 1.— A small flowerpot containing soil was sterilized by moist heat at 110° to 118° C, and protected from drying and dust by a large bell jar. On its surface about 100 cubic centimeters of a bouillon peptone culture of hog cholera bacteria was poured and the whole main- tained moist and at thelaboratory temperature. The soil used was a very fine loam from thegrounds of the Department of Agriculture. The bulk of the soil consisted of grains not larger than j-,\^ milliuieter (..^^^g iuch). Eoll cultures from the soil after a few days demonstrated the presence of immense numbers of bacteria. From this soil rabbits were inocu- lated from time to time by stirring up a little soil in some sterile beef infusion and injecting the clear supernatant li(iuid hypodermically. The soil was infected September 17, 1887. The appended table gives the inoculations into rabbits to test the virulence of the soil. The rab- bits which succumbed died of hog cholera, as indicated by the lesions and the bacteriological examination, 81 No. Date of inocu- lation. Time after in- fection of soil. Died. Kemai'ks. 1 Oct. 10 Oct. 18 Nov. 4 Dec. 12 Jan. 9 Jan. 23 Mos. Days. 23 31 40 2 2.3 3 23 3 23 Oct. 17 Enlargement of spleen ; coagulation-necrosis in liver; hemorrhagic lesions in duodenum and rectum, in lungs and heart; numerous hog cholera bacteria in spleen and liver. Spleen and liver and lungs as in No. 1. Spleen, liver, duodenum, and rectum as in No. 1. Spleen large, pale; coagulation-necrosis in liver slight ; no other lesions ; hog cholera bacteria as in No, 1. 3 Oct. 24 Nov. 12 4 Dec- 23 6 Eeniains Tvell ...do The infectious quality of tliis soil wheii a mouth old was tested on two pigs, by feediug each directly with a tablespoouful of the soil. One showed no disease; the second, a young i^ig, became very sick and was killed on the eighteenth day, being unable to rise. A utopsij. — Animal about eight weeks old, very thin. No skin lesions. Lungs normal, excepting the cephalic and ventral lobes of left lung, the ventral and the root of principal lobe of right lung. These are airless, bright red, mottled with yellowish points, indicating broncho-pneu- monia. The spleen was small. The lymphatic glands of large intestine very large, tough, whitish. The walls of caecum and colon over one- eighth inch thick; do not collapse when slit open. The mucosa is everywhere covered by a lirmly adherent yellowish-white slough, ex- tending as far as rectum. The ileum for about 2 feet from lower end has the mucosa likewise involved in superficial necrosis, but only on the summit of the longitudinal folds. In the stomach a portion of the fundus is covered by a friable deposit made up chiefly of large granular cells with single nucleus. Gelatine and liquid cultures from heart's blood and spleen contain only hog cholera bacteria. The gelatine cult- ures indicate only a moderate number of colonies. The bacteria had also penetrated into the diseased lung tissue. They were obtained on plate cultures, and a rabbit inoculated subcutaueously with some beef infusion in which a bit of lung tissue had been torn up died in eleven days with coagulation necrosis in liver, enlarged spleen, and numerous hog cholera bacteria in both organs. The broncho-pneumonia may have been due to the aspiration of some of the soil during the forced feeding. It has thus been shown that moist soil, not allowed to dry out and kept in a summer temperature ranging from G0° to 05° F., retained its virulence for rabbits from two to three months. At the end of this time fungi and other bacteria had found their way into the pot of soil? as shown in roll cultures. This and other reasons drawn from observa- tions of this germ lead to the conclusion that its life becomes extin- guished with its pathogenic effect on rabbits. This phase of the ques- tion is not to be overlooked, for even if a germ should no longer prove pathogenic, but remain alive, it is not improbable that it may regain its original virulence under certain unknown circumstances. 15612 H c 6 82 The severe disease caused iu the young pig with soil which had been iufected one month ago shows the great susceptibility of young animals to this disease. Since rabbits are most susceptible of any animals to hog cholera virus, it was not thought necessary to experiment on pigs after the former fiiiled to take the disease. It may be argued that the conditions of this experiment were abnor- mal, in that the bacteria were not exposed to the various meteorological conditions, such as rain and drought, freezing and thawing, and the competition with other bacteria in the soil. This is trne. The con- ditions just enumerated are opposed to such a long life in the soil. A condition favoring it, on the other hand, is the low temperature in winter, which may act as a means of preserving the life of bacteria. These objections were partially removed by the following experi- ments: Experiment 2. — A small pot, about 5 inches across the top, filled with soil, is placed in another pot of twice the diameter, also filled with soil in such way that the rims of both are on the same level. In this posi- tion they were sterilized for three and one-half hours, at a temperature of about 110<^ C, in a steam sterilizer. The outer pot was to protect the inner one to some extent from coming iu direct contact with the garden soil in which it was subsequent!}' placed. About 200 cubic cen- timeters of a beef infusion culture of hog cholera bacteria three days old was ultimately mixed with the soil of the inner pot by removing the upper layers and pouring the culture liquid upon the deep layers and then upon the surface, after replacing the superficial layers. The pots were then placed iu the grounds of the Agricultural Department so that the top was level with the surrounding soil. Nothing was placed over the surface to protect them from contamination with ordinary bacteria. The infected soil was placed in the grounds December IG, 1887 During the remainder of December the outdoor temperature oscillated slightly above and below the freezing point, remaining for several days below this point at the end of the month. The soil in the pot was saturated with water during part of the winter and the surface covered with it. It had probably become tightly packed, and hence impervious after the culture liquid had been poured upon it. The appended table indicates the persistence in virulence of the in- fected soil as tested upon rabbits. The soil was taken from the surface of the pot, or from near the bottom as indicated, and the inoculations made as in the preceding experiments : 83 [Soil infected December 16, 1887.] Ko. Date of inocula- tiou. 1 Jan. 5 2 Feb. 1 3 Feb. 7 4 Fob. 2?, 5 Mar. 5 6 Mar. 21 Soil taken from — Su'-face ...do . Depth . SuifrtCt' ..do . . . do . . Number of days afttn- iufoctiou of soil. Rabbit dies- 20 days ranuary 10 . 1 monili 13 days 1 inoiith 19 days 2 iiioiitlis 7 days Februaiy 18 Marcb 5 2 moutbs 18 days . Kemains well 3 mouths o days . . 1 do Eomarka. Oiip lobe of liver involved in coaji- iilation-necrusis ; bacilli of boj; cholera present. Spleen very large, darli; coautila- tion-necrosis in liver; nuiuerous hoj; cholera bacilli in both oigauj. Killed Febrnary27; not diseased. Si)leen and liver as in No. 2; hem- orrhagic lesions in duoileniim and rectum; bog cholci-a bacilli present. Eabbit No. 3 was inoculated with soil from beneath the surface. This was obtained by removing- the inner pot, thmstiiii? a small metallic cork-borer previously tlame, two pots of soil, one within the other, were sterilized as in the preceding experiments. The soil of the inner pof. was saturated from below up with 100 cubic centimeters of a beef infusion culture one day old, of hog cholera bacteria. The whole was buried in the garden on a lev^el with the soil and not protected in 9,ny way. Rabbits were inoculated with the soil as previously indicated . 84 [Soil infected February 20.1 No. Date of inocula- tion. Soil talicn from— Number of days after inoculation. Eemarks. 1 2 3 Mar. 10 Mar. 29 ..do.... Surface — Depth 18 days 38 days ...do Eiibbit dies on eleventh day. Spleen very large ; coagula- tion necrosis in liver ; hog cholera bacilli present. Eabbit died on eighth day ; lesions as in No. 1. Soon after tlie last inoculation the pot of soil was accidentally re- moved by laborers working in the garden, so that tbe experiment came to a premature close. It shows, however, that the bacteria in the depths of the soil were alive thirty-eight days after iuoculation, while at this same time they were dead in the surface layers. Experiment 4. — Soil prepared, sterilized, and infected precisely as in the preceding exi)eriment, was buried in the garden April 4, 1888. The soil soon became packed hard and dry on the surface to a depth of one- half to 1 inch. The foUowiug table gives the inoculations: [Soil infected April 4.] No. Date of inocula- tion. After soil infection. Soil taken from — Remarks. 1 2 3 Apr. 25 ...do.... May 12 ...do 21 days ....do 1 mouth 8 days .do Surface Depth Surface Depth - Surface Depth ....do ... do Dies April 30; enlarged spleen. Slight necrosis in liver. Dies May 2. Same lesions as in No. 1. Kemains alive. Dies May 21. Same as No. 1, besides hemorrhagic lesions in rectum. Kemains alive. 5 6 May 29 ...do.... Juno 15 ...do.... 1 month 25 days .. ....do 7 fi 2 months 11 days.. ...do Dies June 29 ; spleen and liver lesions as in No. 4. 9 in July U ...do .... 3 months 10 days.. .. do ....do do Do. Do. The presence of hog cholera bacteria was demonstrated by cultiva- tion from spleen and heart's blood in all the animals that died. Experiment 5. — Soil sterilized and infected with hog cholera bacteria as in preceding experinients. Placed in the department grounds Ma^^ 18. June 20, surface layer dry and very hard ; boring necessary to get some of it out. Two rabbits inoculated from surface and deep soil. The result of these and subsequent inoculations is givou in the follow- ing table : 85 iSoil infected May 18. 1 No. Date of inocu- lation. Length of time after soil infec- tion. Soil taken from— Ecniarks. 1 June 20 33 daj-3 Surface Depth Surface Depth Dead July 4 (hog cholera). Ueniains well. Do. Do. 9 do -do .. . 3 4 July 20 . . do .... 2 months 2 days. . . ....do Experiment 6. — July 14 a pot of soil was sterilized niul infected through- out with too cubic centimeters of a culture of hog cholera bacilli as before and placed in the Department grounds. No. Date of j Length of time inocula- 1 after soil infec- tion, tion. Soil taken from— Eemarks. 1 Aug. 10 Aug. 10 Aug. 24 Aug. 24 27 days Surface Depth Surface Depth .... Dies August 23! spleen very large. Necrosis in liver ; hog cholera bacilli in spleen ; intestines diseased. Died August 14 ; sjdeen and liver as in No. 1. Remains well. Do. ... do 3 4 1 month 10 days .. ... do These various experiments extended over the coldest as well as the hot- test period of the year, and may therefore lay claim to more or less com- pleteness. They may all be brought together in the following table: No. Date of soil in- tcction. Sept. 17 Dec. IG Feb. 20 Apr. 4 May 18 July 14 Rabbits failed to take the disease when inoculated — With surface soil after- 3 months 23 days 2 months 7 days 1 month 19 days Witli deeper soil after — 1 month 7 daj's . . 1 month 25 days . 2 months 2 daj-s 1 month 10 days . Not completed. 3 months 10 days 33 days. 1 month 10 days. It may be said in general that hog-cholera germs will [)erish in the soil in from two to four months, dependingon the season, moisture, and depth from the surface. In what direction these three factors influence their vitality the experiments are not complete enough to show. We may, however, safel^^ assume that frost has no rapidly destructive effect upon tlieiu, while dryiug (experimeuts 5 and C) seems much more de- structive. Attention has already been called to the destructive effect of alternate wetting and drying. So far as the above results go, a pe- riod of at least four months should be allowed for the natural destruc- tion of hog cholera virus in the superficial laj^er of the soil, /. c, in a layer extending about 2 or 3 inches below the surface. 86 A FEW ADDITIONAL OBSERVATIONS AS TO THE VITALITY OF IlOa CHOLERA VIRUS IN THE SOIL AT THE EXPERIMENTAL STATION. (1) A pen has a coucrete floor, with agentlu slope towards the back. From January to December, 18SG, at least 70 pigs died in tliis pen from liog" cholera. During tliis time all the liquid in tlie pen drained into the field back of it. During February and March of 1887 a number of pigs in this pen died of swine plague. Two survivors from the disease were removed September 15, leaving the pen empty. In December, 1887, the infected ground behind the pen was inclosed, making a yard G feet deep and IG feet long and communicating with tlie i)ei]. Decem- ber 15, 1887, 3 pigs about two months old were placed in the concrete ])en and allowed to run in the yard behind it. All three continued well. To make sure that there were no ulcerations escaping observa- tion one of the pigs was killed one and a half months after their trans- fer to this pen. There were no lesions indicative of hog cholera ; cult- ures from the spleen remained sterile. The two remaining pigs were well three and a half months later. These observations show that ground thoroughly infected for more than a year was free from infectious properties eight moiitiis after the death of the last case. (2) Upon a plot of ground of one-fourth to one-third aero about 100 pigs which had died of cholera during 188G were buried, being covered with li to 2 feet of soil. During 1887 no animals were buried here, but many had been interred within 3 to 8 rods of this plot during the latter half of the present year. A triangular yard 16 feet on each side was fenced off upon the old ground, with a movable pen in. one corner for shelter, December 15, 1887, 3 pigs were penned in this yard. They remained well ; one and a half months later 1 was killed and found healthy. The two remaining ones were well after three and a half months. This experiment shows that ground containing the bodies of numer- ous aiiimals which had died of hog cholera wi^s not infectious after one year. (3) The following notes are valuable in illustrating how rapidly the ground may be freed of infectious matter : A yard 6 by 10 feet was enclosed by a fcm-c and made to communicate with a double pr-n having concrete floors. This pen had been infected by pigs from the outbreak described on page 37. The soil of the yard is a clay loam. ]S\)vemhcr 27. — Nos. 434, 435 now occupy the i)cn and Nos. 4oG, 137 added to day. November 28. — Nos. 434, 435 both die of hog cholera. These had been infected by feeding (see p. 50 for notes on these and other animals in this pen). December 10.— Viscera fiom i^o. 42 fed to Nos. 43G, 437. December 12. — Viscera from No. 43 scattered over the soil of the yard, 87 readily eaten by Nos. 4oG, 437 ; later in the day :N"os. 439, 440, and 443 added. December 17. — Viscera from l^o. 47 and No. 48 scattered over the ground, and Xos. 448 to 453 inclusive placed iu the yard. December 27. — No. 443 dies of cholera. December 28. — No. 448 dies of acute cholera. December 29. -Nos. 43G, 439, 440, 149, and 452 all die of acute cholera. The pen may now be said to bo thoroughly infected. Januarij 1, 1888. — No. 437 found dead. January 3. — Nos. 450, 451, and 453 removed. Januarif 10. — After the yard and pen have been vacant for a week and simply brushed out but not disinfected nor cleaned thoroughly two healthy pigs (Nos. 479, 480) are placed in it to determine whether the ground is still capable of giving the disease. During the greater part of January the ground was frozen over, but during l^'ebruary and March there are frequent, i)rolonged thaws. March 29. — Nos. 479, 480 have remained well since January 10. They are now removed. The yard itself is now converted into a genuine mud-hole. March 30. — Two fresh pigs are transferred to tiiis yard. July 24. — They have remained well for nearly four months. This virus was in the first place either destroyed or made harmless by the prolonged frosts iu January, so that the pen and yard were thoroughly disinfected by natural agencies and perfectly safe two months later. The disease did not reappear in the following midsummer. It may also be seen from the notes that the two i)igs placed in the in- fected pen but one week after the removal of diseased and infected ani- mals did not take the disease, perhaps because the infectious matter was frozen up and slowly killed in this condition before they could get at it. THE EFFECT OF SOME DISINFECTANTS ON THE VIRUS OF HOG CHOLERA. In the report for 18SC there are given in extenso a series of experiments to test the destructive power of the more reliable disinfectants on hog cholera bacilli from liquid cultures usuallj' from one to two days old. The results, owing to their practical importance, are also summarized here. The method employed needs a few comments. A few drops of cult- ure liquid were added to the disinfectaut solution in a sterilized watch glass under a bell glass. After certain regular intervals of time plati- num loops holding about y^^ cubic centimeter were used to transfer this liquid to tubes of beef infusion. These were placed into a ther- mostat and watched for a number of days. The loop of disinfectant carried over into 10 cubic centimeters of sterile beef infusion is diluted to such an extent (about 1,000 times) as to be practically of no account whatever. This method is more sensitive than the method originally employed by Koch. He used bits of silk thread impregnated with the specific organism to be tested and placed them upon plates of gelatine to develop. 88 It has been suggested that hog cholera bacteria may survive in the brine from salted meats long enough to be exported to other countries and communicate the Tiisease. It need not be said that this is impos- sible, for the attenuating action of a concentrated salt solution would be in itself sufficient to speedily destroy the pathogenic power of the bacilli, even if their life were not destroyed. The following experiment shows, however, that they are absolutely killed within four weeks : Ten cubic centimeters of a saturated solution of common salt was added to each of three culture tubes. These were then sterilized and 1 cubic centimeter of a fresh bouillon culture of hog cholera bacilli mixed with the contents of each tube. Small quantities of liquid from one of these tubes were introduced into sterile bouillon every two or three days. Up to the twenty-first day the bouillon became clouded, indicating that the bacilli were still alive in the brine. After the twenty-ninth day the bouillon remained clear. The two remaining tubes of brine hitherto untouched were also found sterile when exam- ined by means of cultivation a day or two later. Mercuric chloride was found destructive to the bacillus when diluted in the proportion of 1 : 75000 (.001^ per cent.). Several drops of a culture were mixed with about 1 cubic centimeter of a .1 per cent, solution, and tubes inoculated from this at the end of two, four, six, eight, and ten minutes. Tubes remain sterile. To show that the antiseptic efl'ect of the liquid transferred with tbe platinum loop was nil, one of these tubes was inoculated again from another cul- ture. This tube was turbid on the following day. Five tubes treated in the same way with .05 per cent, solution. All remain sterile. Five tubes inoculated with bacteria exposed for the same periods of time to a .01 per cent, solution. All remain clear. Five tubes treated as before, using a .005 percent, solution. Perma- nently clear. Five tubes treated as before, using a .002 per cent, solution. All tubes clear, excepting the one inoculated after six nnnutes' exposure. Five tubes inoculated at the end of five, ten, fifteen, twenty, twenty- five, and thirty minutes after exposure to a .001 percent. (1:100000). Tubes inoculated after five and ten minutes turbid next day. On the second day all but the one inoculated after thirty minutes turbid and containing pure cultures of the bacterium. The limit of disinfection for this period of time must therefore lie between 1 : 500000 and 1:100000; hence five tubes were inoculated as above, using a solution of 1 : 75000 at the end of seven, ten, fifteen, twenty, twenty- five, and thirty minutes. All tubes remained clear. Carbolic acid destroys the bacillus in solutions containing from 1 to 1^ per cent, of the acid by weight. Five tubes inoculated after treating bacilli from a liquid culture with a 1 per cent, solution for five, ten, fifteen, twenty, and twenty-five min- utes. All turbid on the following day. The two last tubes were also examined on gelatine plates and the cultures found pure. With a 2 per cent, solution five tubes inoculated after ten, fifteen, twenty, twenty-five, and thirty minutes remained sterile. The same result witn a li ])er cent, solution. With a 1;^ per cent., tubes inocu- lated at the end of seven, ten, fifteen, twenty, twenty-five, and thirty minutes remained clear, excepting the first, which contained bacillus siibtilis. 89 Passings to a one-half percent, solntion, tubes inoculated at the same intervals became turbid with the bacterium sown. With a three-fourths per cent, solution the result was the same. Passing' back to a 1 per cent, solution, tubes inoculated at the same intervals remained sterile. There seems to bean incompatibility between the first and last series. If we examine the others, however, we must conclude that the limit of disinfection lies between 1 and i^ per cent. Iodine 2vater was ])repared by shaking' up some iodine in distilled water, which assumed an amber tint. This solution destroyed the ba- cillus in fifteen minutes, as the following experiment shows: Six tubes were inoculated with bacilli after they had been exposed to the action of the iodine water for seven, ten, fifteen, twenty, twenty- six, and thirty-one minutes. On the following day the first tube became turbid; on the second the teuminute tube was turbid and found to be a i^ure culture of the bacilli sown. The other tubes remained sterile. One of the tubes, inoculated later, showed its capacity for sustaining growth by becoming prompt!}' turbid. Fennanganate of potash. —A series of experiments with this substance, conducted in the manner described above, showed that the bacillus is killed by fifteeu minutes' exposure to .02 j)er cent, solution (1 : 5000). In order to obtain this result a 5 per cent, solution was tried first. Tubco inocidated after an exposure of the virus for seven, ten, fifteen, twenty, twenty-five, and thirt^^-one minutes remained permanently clear. One of these tubes, subsequently inoculated with the unaffected virus, was turbid next day. Two and a half percent., 1 per cent., one-half per cent., one-fourth per cent., one-tenth per cent., and one-twentieth per cent, solutions were tried in the same way. The six tubes used for each solution remained sterile. Finally, a one-fiftieth per cent. (1:5000) was used. Tubes were inoculated after an exposure of the virus for two, four, six, ten, fifteen, twenty, twenty-five, and thirty minutes. On the following day the four first tubes were turbid ; the fifth and seventh remained sterile; the sixth and eighth contained a fine bacillus. The.se two tubes, as was found later, belonged to a lot which, through some carelessness, had not been properly sterilized, and tiie majority became turbid before use. Mercuric iodide was found to destroy the bacillus in solution of 1:1000000 in ten minutes. Two grams of potassium iodide and 1 gram of mercuric iodide were dissolved in 100 cubic centimeters of distilted water, making a 1 per cent, solution of the disinfectant in a 2 per cent solution of potassium iodide. This solution, diluted with sterile distilled water so as to make .1 per cent., killed the bacillus of hog cholera taken from liquid cultures in less than five minutes ; .01 per cent. (1 : 10000), .002 per cent. (2 : 100000), .001 per cent. (1 : 100000), and .0005 per cent. (5: 1000000) destroyed the germ within two minutes. When the solution was diluted so as to make .0002 per cent. (2 : 1000000) and .0001 per cent. (1 : 1000000), it was found that with both solutions tubes inocidated with bacilli, after an exposure of two and five min- utes, were opalescent, the bacilli introduced having multiplied, while the remaining tubes (ten ti> thirty minutes) were sterile. These two solutions, therefore, were still powerful enough to kill the germ in ten 90 minutes. Tlie dilation Lad been carried so far as to make tliem prac- tically equivalent in disinfectiug i)ower. Sulphate of copper. — Tliis disinfectant, which seems to be more effect- ive than most other nutallic salts, was tried in solutions containing 2 per cent., one-half per cent., one tenth per cent. Both the 2 per cent, and the one half per cent, solutions destroyed the germ within five minutes. Tubes inocuhited with bacilli after an exposure to the one- tenth per cent, solution lor five, ten, and fitteen minutes, became tur- bid ; tLose inoculated alter an exposure of twenty, twenty-five, and thirty minutes remained clear. The disinfectant power for short periods of time may be said to lie between one-half and one tenth per cent. Tn this, as in other tests, one or two droi)s of the culture were added to 5 cubic centimeters of the dis- infectant. A slight flocculent precipitate formed each time. Of hyrlrochloric acid a .2 per cent, solution of the acid, made by adding 4.2 cubic centimeters of chemically pure acid (containing about 40 per cent. HGl) to l)a.8 cubic centimeters of water, destroyed the germ in less than five minutes. Chloride of zinc. — A 10 per cent, solution of this salt failed to destroy the vitality of the bacilli in ten minutes; 20 cubic centimeters of (Squibbs) chlorideofziui', containing .50 per cent, of the salt, were added to 80 cubic centimeters of sterile distilled water, to make a 10 ])er cent, solution. A drop from a culture five days old was mixed with G cubic centimeters of this solution, from which mixture tubes were inoculated at the end of five, ten, fifteen, twenty-five, and thirty minutes. The two first tubes became clouded. Sulpihvric acid. — A .05 per cent, solution (1 : 2000) w'as fatal to the ba- cilli of hog cholera in less than ten minutes. Without going into detail, it is sufficient to say that the results weie reached as indicated above. Tubes containing sterile beef broth were inoculated at the end of five, ten, fifteen, twenty, twenty-five, and tliii ty minutes with bacteria exposed to one-half per cent, and one fourth per cent. No development. Those inoculated with one-fortieth per cent. became clouded, each being a pure culture of the bacillus inoculated. When one twentieth per cent, was tried only the five-minute tube be- came clouded. The solution (by weight) was made from sulphuric aoid containing 96 per cent, of the acid (specific gravity 1.838). It must be remembered that the foregoing tests were made upon bac- teria in an active, vegetative state. It is probable that in the dried con- dition it would have taken solutions of the same strength somewhat longer time to destroy their vitality. To briefly summarize the results, placing the least-effective substance first, we obtain the following table : Chloride of zinc in a 10 per cent, solution destroyed the bacilli in liquid cultures in fifteen minutes. Carbolic acid, 1 to 1^ percent. (1:100), in five minutes. Iodine water, in fifteen minutes. Hydrochloric acid, one fifth per cent. (1:500), in less than five minutes. (Only a .2 per cent, solution of this acid tried.) Sulphate of copper, one-tenth per cent. (1:1000), in fifteen to twenty minutes. Sulphuric acid, one-twentieth per cent. (1:2000), in less than ten min. utes. rermanganate of potash, one-fiftieth per cent, (1:5000), in fifteen minutes. 91 Mercuric chloride, one seven liuiulrcd and fiftietli i>er cent. (1:75000), less than five minutes. Mercuric iodide in one ten-tbousaudtli per cent. (1:1000000), in ten minutes. The above table would without doubt be very materially altered if the test had been made with virus mixed with considerable organic matter. This is very well illustrated by the experiments on lime, crude carbolic acid, and additional experiments on sulphuric acid, given in full in the following pages. IMercuric chloride, for instance, often fails completely in albuminous liquids, although it is one of the best destrnctix'e agents of bacteria suspended in water. So permanganate of potash, which would have little or )io disinfectant power in liquids highly charged with organic matter, has a very high power in this direction iu the experi- ments detailed above. The only substances iu the above list, which, iu our estinuitiou, would be useful for purposes of disinfection, are mercuric chloride and car- bolic acid. Of the former, more will be said iu discussing the subject of prevention. Carbolic acid as it usually appears in the market is too ex- pensive tc^be used on a large scale. CRUDE CARBOLIC ACID. Laplace {Deutshe Med. Wochcnschrift, 1888, 121), found that the so- called crude carbolic acid, which will not dissolve in water, is capa- ble of solution when mixed with an equal volume of commercial sul phuric acid. A -L per cent, solution in water of this mixture was suflti- cient to kill anthrax spores within forty-eight hours, and a 2 per cent, solution destroyed them within seventy-two hours. Pure carbolic acid in a 2 jier cent, solution has no effect on anthrax spores. The crude material contains about 25 jier ceot. of carbolic acid. Experiments were made to test the germicide effect on hog cholera bacilli. The crude car- bolic acid used was a very dark, reddish, thick liquid, smelliug strongly of tar, and not translucent even in a layer one-half inch deep. When a drop of this liquid was added to water it broke up into a few globules, which settled to the bottom without undergoing solution. When an equal volume of commercial sulphuric acid was added and the mixture thoroughly shaken, a few drops added to water caused a faint turbidity, but none remained iu a globular condition. When more was added the water assumed a grayish, opalescent appearance, similar to water in which a small quantity of soap is dissolved. To test this mixture, a culture liquid was prepared like that used in testing the disinfecting power of slaked and unslaked lime. (See p. 90.) Beef infusion (to which the white of an egg was added in the pro- l^ortion of one egg to COO cubic ceutiuieters of the infusion) was neutral- ized and sterilized without previous filtration at 110° C. iu Erlenmeyer tlasks, containing each about 150 cubic centimeters. This turbid liquid, with its large quantity of flocculeut material, was inoculated with hog 92 cholera bacilli and allowed to stand for a week. Each flask then re- ceived a certain quantity of the mixture and was thoroughly sliaken up. After certain intervals of time a jdatiuum loop of liquid was withdrawn from each flask, mixed with gelatine, and a roll culture made to indi- cate tbe number of surviving bacilli. To make sure of the vitality of the bacilli in the culture a control culture was made from one of the flasks before adding the disinfectant. Flasks with 150 cubic centimeters culture-liquid, to which was added of the mixture of carbolic and sulphuric acids — J cubic centiraeter=J per cent, (vol). IJ cubic centimeters=l per cent 2i cubic centimeters=l § per cent 3 cubic centimeter8=2 per cent Check tube Number of colonies in roll cultures at the end of— The table shows that a one-half per cent, solution by volume is suffi- cient to destroy the bacilli within one hour. What share the'sulphuric acid has in determining this result can not be inferred unless tried by itself under precisely the same conditions. Tbis is what has been done in the following experiment: Five Erlenineyer flasks, containing each about 150 cubic centimeters of a culture fluid prepared precisely like that in the preceding experi- ment, were inoculated with hog cholera bacilli and allowed to stand at a temperature of 70° to S(P F., for lour days. At the end of this period each drop of the culture medium, as ascertained by roll cultures, con- tained countless bacteria. Commercial sulphuric acid was added fiom a sterilized burette to the flasks in defiiiite in-oportions by volume and roll-cultures made at the end of one, two and a half, tweiitylbur hours, and four days by transferring a minute quantity of the agitated culture on a platinum loop. The accompanying table indicates the result obtained, the specific gravity of the acid being 1.84-- Volume of sul- phuric acid added to 150 c. c. culture- liqiiid. Per cent. by weight. Check. Number of colonies in roll cultures .at the end of— Ouc hour. "ES' ^-:£?- Four days. c. c. .2 .4 .95 1.7 3 .24 .48 1.14 2. 04 3.6 Countless . . ...do Countless. .. 30 None do Countless .. 10 3 None 100 None .. do ... .. ... do None. Do. Do. Do. ' Do. do ...do ...do 93 One half per cent, of sulplmric acid (by weiglit) is thus sufficient to sterilize a richly albuminous liquid in three to four hours. Kemeniber- ing that in the crude carbolic acid mixture the per cent, of sulphuric acid (by weight) contained in the one half per cent, solution (which was capable of sterilizing a simih^r liquid in one hour) was .oO, we must conclude that there can be no great difference between the crude car- bolic acid mixture and the sulphuric acid in regard to disinfecting power. We shall, however, recommend the former in disinfection, since it may lust longer in the soil in which sulphuric acid soon forms sulphates and thereby loses its germicide properties. According to experiments giveu ou page 90, .05 per cent, sulphuric acid was sufficient to destroy hog cholera bacilli in ten minutes when no organic matter was present. In the above experiment, in which the liquid contained much organic matter, about ten times as much was necessary. ORDINARY LIME AS A DISINFECTANT FOR HOG CHOLERA. Eecent experiments made with ordinary lime (CaO) by Liborius {ZeitscJinff f. Hygiene II, 1887, p. 15) have shown that water containing but .0074 per cent, of lime is capable of destroying typhoid bacilli in the course of a few hours. Cholera spirilla are destroyed by a solution con- taining .0246 per cent, of lime. These two diseases resemble hog chol- era in the mode of dissemination of the virus. In all, the stools are the chief vehicle of the bacteria. Disinfection, therefore, becomes a most important aid in the prevention of the disease. Lime has many advantages over other disinfectants. It is, first of all, not poisonous. It may be used almost anywhere with imi^unity where mercuric chloride or strong acids are inapplicable. The soil, when containing the germs of the disease, is not injured by being covered with a small quantity of powdered or slaked lime. The material is ex- ceedingly cheap and can always be obtained without difficulty. The experiments given in the following images show that lime is a very effi- cient disinfectant with reference to hog cholera virus, and therefore with reference to the bacteria of swine plague, which are far less resistant than the former. The method is, in the main, based upon that used by Liborius, with some modifications, which it is not necessary to point out here. (1) It was desirable to observe what percentage of lime in solution was necessary to destroy hog cholera bacteria not mixed with any ap- preciable quantity of organic matter. For this purpose water contain- ing different quantities of lime in solution received about two drops from a beef-infusion culture, each drop containing approximately 500,000 bac- bacteria. Attheeudof one-half hour aboutone-thirtiethcubiccentimeter of the fluid (usually 8 to 10 cubic centimeters) was removed with a flamed platinum spiral and transferred to liquefied gelatine in a test tube. The same was done at the end of three hours. This tube was then placed in ice water and twirled between the fingers while in a horizontal position. 94 The gelatine, as it coiigealecl, uiiifornil.v coated the luside of tbe test tube, wliicli was immediately trausfericd !o a box in connection with a refrig- erator, where it was kept at a temperature of 75° F.* The temperature of the laboratory during these experiments was frequently as high as 95° F., scarcely ever below S(P F., (July). Any bacteria not killed by the disin- fectant would show as minute yellowish-white points in the layer of gel- atine within forty-eight hours. The number of points corresponded to the number of living bacteria introduced into the gelatine. These cul- tures will be denominated roll cultures in the succeeding images. By this method it was found that lime-water diluted with three times the quan- tity of distilled water was sufficient to destroy hog cholora bacteria in one-half hour. A dilution containing six times the quantity of water destroyed the bacteria in three hours, while a dilution containing twelve times the quantity of water was not capable of destroying them in twenty-four hours. If we take .12 per cent, as the quantity of lime in lime-water, .03 per cent, of lime will destroy all bacteria in one-half hour, .019 per cent, in three hours. Lime-water diluted so as to contain of CaO. 0.072 per cent . O.OG per cent .. 0.04 per cent.. 0.03 per cent. Number of colonies in roll cultures prepared at the end of — Liquid cultures inoculated at the end of twenty-four hours. Check tube Countless II. 0.03 per cent | None. 0.010 per cent 0.0092 per cent Check tube Very many. ....do Countless. None ....do ■ Very many Sterile. Do. Turbid. * Contains hay bacilli. The quantity of the disinfectant used must be increased, with many disinfectants, with the quantity of organic matter present in the mate- rial to be disinfected. The preceding experiment gives us therefore only the minimum quantity that is necessary to destroy hog cholera bacilli when organic matter is practically absent. A second series of experiments was therefore made by mixing beef infusion cultures with varying proportions of lime-water, and observing *A (iescriptiou of this method is given by it^ author, .^, Esmarch, iu the '/^eitschrift fur Hijfjiene, i (1886), Tp. 293, 95 the quantity necessary to destroy all bacteria present. A preliminary ex- periment was made by adding- lime water in varying proportions to cult- ure tubes containing about 10 cubic centimeters each of beef infusion which had been inoculated the day before and were now opalescent. A tlocculent precipitate formed after the addition of the lime-water, which soon settled to the bottom, the quantity of this precipitate varying di- rectly with the amount of lime water added. The following table shows that in all the cultures macle by transferring a loop of tlie mixture of cult- ure liquid and lime-water in the proportions there given at the end of thirty minutes, four hours, and twenty-seven hours, no destruction or retardation of bacterial growth could bo detected. In the first tube con- taining beef infusion and lime-water in the ratio of 2 to 1 the precipitate left at first a perfectly clear supernatant liquid. This did not, however, mean complete disinfection, as the roll cultures proved. Moreover, at the end of three or four days this liquid became opalescent again, owing to the rapid unchecked multiplication of the contained bacteria. A quantity of lime amounting to .04 per cent, was not sufficient to destroy the vitality of beef infusion cultures. III. a o a) Lime water. Lime. Number of colonies in roll cultures prepared at the end of — One-half Lour. Four hours. ■ Twenty-seven hours. Seven days. c. c. 10 10 10 10 10* c.c. 5 1 i Per cent. .01 .02 .01 .0057 Couutkss . . do Countless ...do Countless . do . Countless. Do ...do .... ...do ... ...do .... ... do ... . ...do ■ ...do .... ....do r-. * Check. This experiment was therefore continued with relatively larger quan- tities of lime. Four portions of 40 cubic centimeters each of beef infu- sion in culture tlasks, in which hog cholera bacteria had multiplied for twenty-four hours, were mixed respectively with one-half, one, one and one-half, and two volumes of lime-water, and thoroughly shaken. It was found by testing with roll cultures at the end of thirty minutes, four, and twenty-seven hours that for every 40 cubic centimeters of culture liquid it required GO cubic centimeters of lime-water to destroy all bac- teria within twenty-seven hours, while a large number were destroyed within four hours. It required 80 cubic centimeters to completely- ster- ilize the culture fluid in four hours, although nearly all bacteria were destroyed within the first half hour. In the flask to which 40 cubic centimeters had been added there was a partial destruction of bacteria at the end of twenty-seven hours. At the end of six days the bacteria 96 were as numerous as in the flask coutainiug 20 cubic centimeters of lime-water, in which uo destruction of bacteria or retardation of growth could be observed. The percentage of lime in these cultures is given in the following table : IV. a o a a M c. c. 40 40 40 40 Lime- water. Lime. Nui:ber of colonies in roll cultures prepared at the end of— One-half hour. Fourhours. Twenty- seven hours. Six days. c. c. 20 40 CO 80 Per cent. .04 .00 .072 .08 Countless . ....do Countless . ....do Countless . Very many. None ...do ... Countless. None. ....do A few .... A few When the lime-water was added to the beef infusion a light flocculent })recipitate was formed immediately as in the preceding experiment, the quantit.y depending on the amount of lime-water added. This set- tled to the bottom in a very short time, leaving a perfectly clear, slightly yellowish layer of liquid above. In those flasks, however, iu which dis- infection was not accomplished, this layer of liquid remained turbid, or else became clear at first, with the partial destruction or precipitation of bacteria, and then became clouded again as the remaining bacteria multiplied in it. The quantity of organic matter which is present iu substances to be disinfected is ordinarily quite large. This is true of bowel discharges which contain the specific hog cholera bacteria, and which should there- fore be thoroughly disinfected. To prepare a solution containing a con- siderable amount of insoluble albuminous matter, the method of Liborius was adopted. Beef was chopped finely and allowed to soak over night in the refrigerator in twice its weight of water, as in the preparation of beef infusion. After the meat had been removed from the liquid in a press the latter was neutralized and the white of an egg was added in the ratio of one Q:g,g to every 600 cubic centimeters of liquid. The whole was boiled and the coagulated masses allowed to remaiu in the liquid. The amount of solid particles and lumps, when deposited on the bottom, formed a layer nearly as deep as that of the liquid above it. This mass of liquid and solid matter was placed in Erlenmeyer flasks, each receiving 150 cubic centimeters. The whole was sterilized for sev- eral hours at a steam pressure of 12 pounds and subsequently inoculated with hog cholera bacteria. At the end of three days, when each drop of the culture liquid contained nearly a million of bacteria, milk of lime, made by adding lime in the ratio of one gram to 9 cubic centimeters of 97 water, or, iu other words, milk of lime coutaiuiDg 10 per cent, of lime, was added iu various quantities as sbowu by the following table; No. Beef infusion. Milk Number of colonies in roll cultures made at the end of — of Lime. Lime. One-half hour. Tliiee hours. Twenty- four hours. Six days. 1 2 4 5 c. c. 150 150 150 150 150 (§) c. c. Per cent. 40 2.1 20 1.2 None ...do ...dot .... ....dot .... Very many. Conntles.s. None* ....do None ... ..do None. Very many. 10 5 2 .62 .32 .13 ....do ....do Very many. . . do . . . ....do .. 50 '■About 12 funsi. t About 100 fuiisi. § Check (beef infusion). In all the experiments the cultures coutaiuing tiie preci])itated mat- ter were shaken up before testing so that the quantity taken for the roll cultures (about ^j^ to J„ cubic centimeter on a spiral ot platinum) consisted of solid particles as well as liquid. Within thirty minutes after the addition of the milk of lime the pre- cipitate had settled so as to leave the supernatant liquid perfectly clear in flasks 1, 2, and 3; in flasks 4 and 5 it was still tuibid as be- fore the addition of the lime. It cleared up in Ko. 4 soon after, but re- mained permanently turbid iu No. o. In none of the other flasks did this layer become turbid even after seven days. In these the bacteria were permanently destroyed, as the table shows. That the lime trans- ferred to the roll cultures could have had no retarding effect on the growth of any bacilli present was proved by adding at least four times the quantity of lime to a gelatine tube which had been inoculated with a drop of culture fluid. Countless colonies appeared in the gelatine layer in due time. The check tubes were tested o dy at the beginning of every experiment to test the vitality of the cultures used. Since hog cholera bacteria will remain alive m the beef infusion employed for weeks and months, there was nothing to be gained in making loll cult- ures from these check tubes more than once. The table shows that 5 cubic centimeters of a 10 per cent, milk of lime was sutBeient to sterilize within one-half hour 150 cubic centime- ters beef infusion containing much suspended albuminous matter. This would be equivalent to about one half gram of ordinary unslaked lime, or about .0032 gram for every cubic centimeter of liquid, i. e., .32 per cent. We may assume, therefore, that for every twenty pounds of fecal matter or discharges from diseased pigs only one ounce of lime in the form of milk of lime is needed, provided the two are thoroughly 15G12 II c — -7 98 mixed. The less complete this mixing- can be the more lime must be added to make the disinfection thorough. By compariug the amount of lime necessary when there is little or no albuminous or other organic matter present and when there is a large quantity of it, we are im- pressed with the importance of alwaj'S taking into consideration the circumstances under which disinfection is to take place. Thus the bacteria of hog cholera are destroyed in one-half hour when placed in water containing only .03 per cent, of lime. When there is i)resent beef infusion diluted to one third the original strength it requires .08 per cent, of lime. When the suspended albuminous matter is consid- erable it requires .32 per cent. It may be more convenient to use unslaked lime either in small lumps or powdered shortly before application to the mass to be disinfected. That this may be done the following experiments are sufficient proof: Erlenmeyer flasks, containing each from 100 to 200 cubic centimeters of beef infusion in which there was a large amount of suspended mat- ter, as in the preceding experiment, were used for this purpose. After inoculating each with hog cholera bacteria they were allowed to stand for forty-eight hours. At the end of this time the flasks contained raanj^ millions of germs in each cubic centimeter. Unslaked lime was broken up into lumps as large as peas or beans, and thoroughly heated over a Buusen flame to destroy any adherent spores and drive away any moist- ure. After cooling, this was thrown into the culture-flasks in the pro- portion, by weight, of 2, 1, ^, and | per cent., respectively. The flasks became very slightly warmer. After thorough shaking the sus[>ended matter soon began to settle down, leaving a clear, supernatant liquid, which remained clear after ten days' observation. The liquid in the last flask (^ per cent, lime) cleared up most tardily. The attached table shows that even as little lime as .^ gram in 100 cubic centimeters was sufficient to x)ermanently destroy all bacteria in a liquid very ricli in albuminous substances. Even at the end of eight days the flasks containing the smallest amounts of lime were s'terile. * VI. Beef infusion. Percent, of CaO. Number of colonies developed in roll culture pre- pared with j'j cubic cenlimetor ot infusion at the end of— One hour. Four liours. None A fow Xono ... do Twenty- four hours. Eight day.s. 100 cubic centimeters plus 2 grams CaO . 120 cubic centimeter.s pi us 1.2 grams CaO 200 cubic centimeters plus 1 gram CaO. 200 cubic centimeters plus .5 gram CaO. 2 1 .5 .25 None ....do Very r.! an J. . ...do None . do , . do .. do Noue. Do. The table shows that in the flasks containing one-half and one-fourth per cent, of lime there were still a considerable number of living bacteria 99 at the end of the first hour, altlioui;li destroyed at the eud of four hours. The presence of bacteria in the fiask containing 1 per cent, of lime at the end of four hours, although none were detected at the end of the first hour, shows that all bacteria are not necessarily destroyed simul- taneously. A second experiment, conducted precisely as the preceding, confirmed the latter in every respect. The quantities were chosen somewhat dif- ferently, as the appended table shows, in order to find out the lowest percentage of lime that will destroy all bacteria within a given period of time. VII. Lime. Number of colonies in roll cultures made with jV cubic centimeter of the beef infusion at tliie eud of — Beef infusion. One hour. Three hours. Twenty- four hours. Five days. 100 cubic centimeters plus 1 grain CaO 200 cubic centimeters plus 1 gram CaO . . . 200 cubic centimeters plus . 5 gram CaO . . - 200 cubic centimeters plus . 3 gram CaO . . . Percent. 1 -J .15 Very many . None Very many . Countless. .. ....do None ....do 50 Very many.. None . . . ...do.... ...do.... 50 None. Do. Do. Do. The lime was powdered, and heated in a platinum evaporator to de- stroy all adlierent spores. There was scarcely any perceptible rise of temperature when the lime was added to the liquid. The first flask con- tained a culture eight days old, the remainder contained cultures four days old. From the table it will be seen that one-half per cent, of un- slaked lime is sufficient to sterilize a very turbid albuminous liquid in four hours, one fourth per cent, in twenty-four hours. Fifteen-huu- dredths percent, was almost enough to destroy all the ge^ms in one daj" while at the end of five days all were dead. DISINFECTION OF THE SOIL WITH LIME. The same fine loam used in the experiments to determine the vitality of hog cholera bacteria in the soil was nsed here. The method pur- sued was briefly as follows : Into small beakers, plugged with cotton wool and sterilized at 150° C. for several hours, about 50 grams of slightly moist soil was intro- duced, and the whole sterilized under steam pressure at 110° O. About 10 cubic centimeters of a beef-infusion culture of hog cholera bacteria was then stirred up with it. After a certain length of time milk of lime was added and thoroughly mixed with the soil. The destruction of the bacteria was noted at certain intervals of time by taking small bits of the soil on a platinum loop and making roll cultures therefrom. 100 The table appended gives the results of a series of experiments carried out according to tliis plan : Quantity of lime in soil. Check culture Number of colonies in roll cultures prepared from a small bit of soil after— Number aud date of experiments. One-half to one hour. Three to four bours. One day. Two days. Three days. Five days. Six days. Seven days. 1888. T.— Jan. 18 Per cent. 1 2 h i i i i i 1 2. 4 1 'oo GO 00 00 00 (') (') 00 00 00 00 100 ■10 {') (-) 00 30 2.30 12 n II.— Jan. 20 III. -Jan. 23 3-4 1000 20 8 GO 10 I v.- Jan. 24 v.— .Jan. 31 00 C) VI.— Jan. 31 VII.— Feb. 10 00 Vni.-Feb.lO IX. -Feb. 23=.... (*) X.— Feb. 23 5 XL— June 7'- ... XII.— June?' ' Countless colonies. 2 Less than oc, but still too numerous too be esti- mated. ^ Fungi present. ■* A few fungi present. = Babbit died of hog chokr.i aftir inoculation with soil on nineteenth day. ^ A microccus multiplies in the soil. ' Kabbit inoculated with soil on clcveuth day remains alive. Tlie following may serve to explain more fully the tabulated experi- ments and results obtained: I. Fifty grams sterile moist soil, infected with 10 cubic centimeters of a beef-infusion culture January 5. January IS: 5 cubic centimeters of a 10 per cent, milk of lime (9 cubic centimeters water and 1 gram ordinary unslaked lime) was stirred up with it. This is equivalent to 1 per cent, of lime. A roll culture from the infected soil was made in all exi)eriments before the lime was added, to make sure of the pres ence of living germs. • Eoll cultures, to which three loops of milk of lime were added, showed no diminution in the growth of colonies, ])roving that the small amount of lime (fraction of a loop) added with the soil had no retarding effect. In this experiment 1 per cent, lime was suflicieut to remove from the soil countless bacteria (as shown by check-roll) in three to four hours. II. January 20 : To another beaker of soil, prepared and infected with the preceding, 2 percent, milk of lime was added and stirred up. The result identical with Experiment I. III. January 23: 2i cubic centimeters of 10 per cent, milk of lime added (= .J percent.). The check-tube contains so many colonies as to have an opalescent appearance. Disinfection is nearly completed after one hour. A few colonies develop in the one day and three day tube. IV. January 21: 1| cubic centimeters of 10 per cent, milk of lime (= 1 per cent.); no disinfection is brought about. During the first twenty-four hours there is a decided diminution in the number of colo- nies, but a decided increase thereafter. V. VI. January 31 : The sterile soil in two beakers was infected yes- terday with a beef infusion peptone culture three days old, 10 cubic centimeters being added to each beaker. Today enough milk of lime 101 (5 per cent.) is added to two beakers to make one-lialf per cent, aud one-quarter per cent., respectively. The check tubes show subsequently countless colonies. The table shows a slight diminution in the number of colonies for the first twenty-four hours, then an increase. JS'o disin- fection. For the one-half per cent, beaker there is apparently a complete destruction during- the first two days, but subsequently the few remain- ing multiplied again. No disinfection here. This result seems to disa- gree with the third experiment. The discrepancy was, however, caused by the fact that the milk of lime was not thoroughly shaken up when used. YU, VIII. In these experiments the lime was thoroughly stirred up before use, and in both beakers disinfection has taken place. The germs in the soil before adding the lime were not so numerous, because the soil had been infected from a liquid culture only fifteen minutes previous and no multiplication could have taken place. IX, X. The conditions of the experiment are the same as before. The soil is infected with a liquid culture two days old. Seven days later check-tubes are prepared from each beaker of soil. One receives one-half per cent, lime, the other three-quarters per cent. {I. e., 5 cubic centimeters and 7.5 cubic centimeters of a 5 per cent, milk of lime to 50 grams soil). The table shows that the beakers were invaded by a mi- crococcus after the first day, which multiplied enormously in the soil, so that hog cholera colonies could not be detected. After nineteen days two rabbits, inoculated with a little infusion made from the soil, suc- cumbed to hog cholera. March 13: Eabbit inoculated subcutaneously with sterile beef infusion, in which a little of the one-half per cent, lime soil had been stirred up. Kabbit dead March 19. Spleen enlarged, congested; kidneys, lungs, and duodenum with hemorrhagic foci. Beginning necrosis in liver. A second rabbit inoculated from the three-quarters per cent. lime soil in the same way and at the same time. Eabbit dead March 21. Lesions the same, in addition to a hemorrhagic condition of the lower portion of large intestine. In both hog cholera bacteria present. XI, XII. Experiments carried out as the preceding ones. The bac- teria were permanently destroyed, as shown by the roll cultures made up to the seventh day, and unsuccessful inoculation of rabbits later on the eleventh day. From these experiments we may conclude that three-quarters to one per cent, of lime will destroy hog cholera bacilli in the soil. It is highly probable that a smaller per cent, of lime (one quarter to one-half per cent.) will be amply sufficient when simply scattered in a thin layer over the surface where the great majority of tlie disease germs will remain until destroyed by natural agencies. IS THERE ANY RESISTANT SPORE STATE IN THE LIFE HISTORY OF THE BACILLUS OF HOG CHOLERA? This question can now be answered with the help of the foregoing experiments. Stained in dilute aqueous solutions of aniline colors the bacilli from the tissues of animals which have succumbed to the disease stain in such a way as to leave the impression that each bacillus contains an endospore. A narrow band of stained substance bounds an oval pale 102 body, which is but slightly tiuged. It appears that a rather resistant envelope prevents the coloring matter from passing readily into the in- terior of the bacilli. If a drop from a recent liquid culture be suspended from the lower surface of a cover-glass and examined in a glass cell witli a homogene- ous immersion objective and. small diaphragm, the following appear- ances are worthy of record : The bacteria in the center of the drop of culture fluid are in very active motion. If the periphery of the drop be examined there will be found a dense layer of bacteria caught there by the slow desiccation and consequent contraction of the drop. These, some of which are still moving slowly, appear slightly larger than the forms in the center of the drop. As the drying proceeds and the film of water becomes thin, the bacteria appear to be made up of a distinct dark border surrounding an almost transparent body. In most forms there is a slightly thicker border at the ends than at the sides of the short, rod-like bodies. When stained slightly this border takes the stain well, while the body of the rod remains pale. The fact that the structural and color pictures correspond is strong evidence that the microbe possesses a rather dense membrane, which in optical section is seen as a narrow dark border. Involution forms may occasionally simulate endogenous spore forma- tion. When hog cholera bacilli are placed upon the surface of gelatine with a drop or two of blood, a few days are sufficient for the formation of a large number of filaments from two to many times the length of the bacilli as they are found in the tissues of animals. The ends are rounded or irregularly pointed ; the width of the bacilli varies ; in gen- eral, they have the physiognomy of abnormal forms. In each bacillus there may be from one to four oval, square, or oblong, clear spaces. When stained they remain without color, thus simulating spores. When carefull}' examined in a fresh condition, there isnorefrangibility — they are mere holes or spaces left by the irregular breaking up and retrac- tion of the protoplasm. Microscopical characters, however, are now aiid then misleading, un- less we interpret them by physiological experiments. Judging from what have hitherto been considered properties of bacterial spores, the microbe of hog cholera can not lay any claim to the production of true endogenous spores. Their absence is determined by results of experi- ments recorded in the preceding pages : (1) The thermal death-point of the bacilli at 58° 0. An exposure to this temperature for fifteen to twenty minutes destroys not only the vi- tality of cultures of all ages, but also the germ in the tissues of the in- fected animal. A momentary exposure to boiling water is equally effi- cacious. (2) The bacteria are destroyed by disinfectants in solutions which are incapable of destroying spores. 103 (3) They are killed by simple dryiug- far more quickly than are spores; at the same time their resistance to drying is much greater than might be expected under the circumstances. In the experiments recorded some dried bacteria in spleen pulp were killed in less than a month ; otheis resisted lorty-nine d,\ys. For cultures we may put the limit, ac- cording to experimental data, between one and four months. It is this continued vitality in the dried state that suggests the existence of a membrane which is more resistant than that i)Ossessed by the great majority of bacteria in their vegetative state. (4) Subjected to various conditions of moisture and dryness, of freez- ing and thawing in the snperticial layers of the soil, they are destroyed after an exposure of between two and four months. The facts brought out by the study of the bacillus lead to the con- clusion that a distinct spore state, so called, does not appear either within the animal body or in nature. WAYS IiN WHICH SWIiNE BECOME LNFECTED. BY WAY OF THE DIGESTIVE TRACT. (a) Feeding diseased viscera. — In at least 90 per cent, of swine, hog cholera may be induced by feeding to them the visceraof animals which have died of the disease. The lesions produced are exceedingly severe. The mucous membrane of the large, intestine is extensively ulcerated or comiiletely necrosed. In animals which have contracted the disease in the ordinary way in infected pens the ulceration of the large intes- tine, at times very severe, usually stops abruptly at theileo ca'cal valve. When this is slit up, the mucosa belonging to the small intestine up to the free border of the valve is in the great majority of cases normal, while the mucosa of that surface of the valve facing the ca-cum may be extensively ulcerated. In many animals fed with infectious matter the ulceration involves the entire ileum. This is well illustrated by the following cases : January 8, 1886. — Pig No. 1G5 was fed with the viscera of two i)igs which had died of hog cholera. It was found dead January 20, after manifesting no marked symptoms of disease except a tendency to lio, quietly in its pen. On examination the subcutaneous fat was found diffusely reddened. There was a slight peritonitis, indicated by a con- siderable quantity of straw-colored effusion and some fibrinous stringy deposits. There were also a few local excrescences on the small intes- tine, due to the irritation ot echinorhynclii, ISplcen somewhat enlarged ; on its surface a few bright red punctiform elevations. Eight heart dis- tended with a clot. Local hepatizations in lungs, probably caused by lung worms, which were very numerous. Stomach but slightly reddened. A numberof ulcers in the duodenum, the mucosa of which was reddened. The mucosa of the ileum for li feet from valve was completely ne- crosed, the walls thickened, and the serosa of this portion dotted with ecchymoscs. On the upper portion of the ileum there were scattered ulcerations on a deei)ly congested membrane for G or 7 feet. The entire length of the large intestine was covered with dirty, yellowish ulcera- tions varying in diameter from a pin's head to nearly an inch. The mucosa itself was very deeply congested in the caecum and colon, and the walls much thickened. Ascarides and eclmiorliijnchi num«»rous in small intestines. The liver attached to diaphragm in several places by a whitish exudate. A tube of meat infusion with peptone inoculated from the spleen of this animal was found to be a pure culture of the motile bacillus of hog cholera. Line cultures on gelatine plates confirmed the microscopic examination. A tube of nutritive gelatine inoculated from the spleen at the same time contained in each needle-track, several days later, from ten to fifteen colonies of the same organism. Two cover-glass pre- parations revealed no bacteria. This fact, combined tVith the small number of colonies in the tube culture, gave evidence of the small num- 105 106 ber of germs in the spleen tissne. Inocnlations on mice and guinea- pigs gave substantially the same results as those obtained hitherto. No. 159 was fed with viscera of No. 1G5 on Januar^^ 28. Febru- ary 5, its eyes were sore and nearly closed ; it was quite weak. It died the following day, only eight days after infection. The skin ou ab- domen was reddened in patches; the subcutaneous tissue diifusely. The superticial inguinals, as well as the. glands in the abdomen, were deei)ly congested, the cortex more especially. Tliose of the thorax were nearly pale. The spleen was dotted with a few i)anctiform t)lood- red elevations. Beneath the epicardium and endocardium of both auri- cles and the endocardium of the left ventricle were extensive patches of extravasated blood. Kidneys enlarged and congested throughout. The lesions of the ileum, caecum, and colon in this animal were quite as extensive as those of the case just described ; there were no ulcers in the rectum, however. Those of the colon had black centers, point- ing to a recent origin from blood extravasations on the surface of the mucous membrane. In the spleen of this case the characteristic bacteria of hog cholera were exceedingly numerous, as determined by cover-glass preparations. Two liquid cultures proved pure when tested on gelatine plates. In the needle tracks of a tube culture in gelatine innumerable colonies ap- peared in afew^ days. Inoculations into animals from subsequent cult- ures proved equally positive. Pig No. 15C was fed with the viscera of No. 159 February 18, and after manifesting the usual symptoms of hog cholera, died February 25, seven days after feeding. Among the marked lesions produced by the disease was a complete necrosis of the upper two thirds of the colon, with scattered ulcers along the lower third. Eight feet of the lower ])ortion of the small intestine, beginning at the valve, was necrosed. In the spleen there were numerous small grayish spots, probably cen- ters of necrosis, as they showed no longer cell structure when crushed on a slide and stained. The fundus of the stomach was also deeply congested. The spleen, to which organ the microscopic examination was limited, contained the characteristic bjicteria, as shown b}' cover-glass prepara- tions. Three liquid cultures made from the same organ were found to be pure cultures of the same microbe when tested by line cultures. A tube culture in gelatine developed in each needle track numerous nonlique- fying colonies. In these animals the mode of introduction of the virus determined the seat of the severest lesions. It is probable that the food passes quite rapidly through the small intestine; that in the stomach the action of the bacteria is more or less limited, because they have not sufficient time to'multi[)ly, and probably because hindered by the acid condition of the organ, though they will multiply with considerable vigor in slightly acid solutions. The prolonged stay of the food in the large in- testine permits multiplication, and thereby causes the first and severest lesions to appear here. When these have become very extensive, so as to paralyze the action of the large intestine, the ileum becomes involved in a similar manner, possibly by a partial stoppage of the infectious matter in this portion of the intestine. It may therefore be said, in general, that the feeding of hog cholera viscera produces lesions like those found in natural infection, only more 107 severe and more extensive. The duration of tbe malady is also mucb shortened. The notes £;iven above are quoted from one of the reports of the Bureau. Since they were written numerous other pigs have been fed in this way in the course of vaccination and other experiments with precisely the same result. We must therefore emphatically deny the truth of statements made now and then in agricultural journals that hog cholera can not be communicated to healthy swine feeding upon the vis- cera of those dead from this disease. Such statements are pernicious in tendency, and aggravate the evil which this malady carries with it. * (b) Feeding imre cultures of hog cholera bacilli. — The successful re- production of this disease by feeding inue cultures of hog cholera bac- teria proves not only that the bacteria fed are the true cause of the disease, but also that infection may and does take place in this way. We again quote from the report for 1880 some experiments which demonstrate that swine may take the disease and die by simply swal- lowing somewhat more than half a pint of beef broth in which hog cholera bacteria were growing. December 13, 1886. — Three pigs were fed with 300 cubic centimeters each (three fifths of a pint) of a beef-infusion culture of liog cholera ba- cilli kept in the thermostat, at 95° F., for three days. The culture was contained in two flasks. When examined both Avere found pure. The l)igs were prepared for the feeding as follows: No. :U8 received no food for over twenty-four hours. A 2 per cent, solution of sodium carbonate in beef infusion was then given to increase the alkalinity of the stomach. Of this about 1 liter was consumed. It was then fed witli 300 cubic cen- tiuieters of culture liquid mixed with beef broth to make 1 liter. No. 350 was starved in the same way, but received no alkali before consum- ing the culture. No. 312 was not deprived of food before eating the cult- ure. The result confirmed our anticipations. No. 348 showed signs of disease in two days. On the third it was unable to rise, and died on the same day. The post-mortem examination showed a considerable congestion of the mucous membrane of the duodenum and jejunum, as well as of the large intestine. The fundus of stomach affected in the same way. The liver was gorged with blood, as well as the portal system. There were no marked lesions of the other viscera. That hog cholera bacilli had also entered the blood was shown by two pure cult- ures in beef infusion obtained from the spleen. A gelatine culture from the liver contained about six or seven colonies. No. 350 was a more typical case, and demonstrated the severe local effects of the bacillus much better, since the animal lived longer. It ate fairly well until the fourth day, when its appetite gave way and diarrhea set in. From this time it grew weak and thin, being scarcely able to walk. It died on the tenth day after feeding. The lesions of the alimentary tract were exceedingly grave. Beginning with the stomach, the mucous membrane was dotted with closely-set elevated masses as large as split peas, and larger patches of a whitish viscid sub- stance, made up entirely of cellular elements (diphtheritic ?). When removed, a raw, depressed surface was exposed. The membrane itself * It may bo possible that those who make this claim vrerc coufiouted with swine plaj^uo. This disease, although I'escmbliiig hog cholera yery closely in many features, we have not been able to reproduce by feeding. 108 was pale. Besides a general injection of the ileum, Peyei's patches were more deeply congested, and the uppermost covered with a thin, yellow- ish film, not removable, and most likely dead epithelium. In the cae- cum and colon the mucosa was superficially necrosed, and converted into a continuous layer of a dirty whitish mass about 1"'°' thick. The walls of the intestine were greatly thickened and veiy friable. Microscoi^ic sections showed an extensive cellular infiltration of the submucous connective tissue which had separated the masses of fat cells, concealed the connective tissue fibers, and caused a great thick- ening of the entire layer. The mucosa itself was greatly altered. The surface was necrosed and converted into an amorphous mass. In some l)]aces the necrosis involved the entire depth of the crypts of Lieber- kiihu, a series of t^trite indicating their former existence. Those whose epitlielium still remained were plugged with a cylindrical nn\ss, inclos- ing broken-down nuclei. The bacteria had exerted their poisonous effects from the surface of the mucosa towards the dei)ths, destroying the surface epithelium and glandular structures and involving second- arily the submucous layer. Near the rectum this continuous mass of dead tissue was replaced by isolated ulcers embedded in an intensely reddened mucosa. The ileo-C5iecal valve was much swollen, but the necrosis did not extend into the ileum, although there were a few ulcers near the valve, and the epithelium had a pale, lusterless aspect, as if dead. The liver was filled with blood, which readily clotted as it flowed from the cut surface. Spleen congested and but slightly' enlarged. Lungs hypostatic. The lypmphatic glands in general not much aflected. Two liquid cultures from the blood were turbid next day, and contained hog cholera bacilli only. In a gelatine tube culture from the liver about a dozen colonies developed in each needle-track. No. 342, which was fed with the same quantity of culture licpiid, but was not deprived of food previously, was somewhat ill on the folio wing day. It recovered, however, and continued apparently well for several weeks. It began thereupon to grow thin and weak. On January 20 it was no longer able to rise, and was therefore killed for examination, in order to conclude the experiment. On opening the abdominal cavity it was at once perceived that the animal had been suffering from a very intense disease of the large intestine, ai)ortion of which was firmly attached to the bladder. When dissected out and slit open, the mucous membrane of the CiBcuin and colon was found replaced by a brownish friable layer of necrosed tissue. The wall of the intesMue was infiltrated to such an extent that it was nearly one-fourth inch thick, and so degenerated that the forceps easily' tore through it. The thickness of the walls pre- vented the intestine from collapsing- after it was opened. Its oidy con- tents was a brownish liquid mass. The glands of the nieso colon were very large, some like horse-chestnuts. On section the entire tissue was very pale, almost white. The spleen was somewhat enlarged ; the Mal- pighian corpuscles unusually large and prominent on section. Lungs and heart normal ; kidneys deeply reddrned throughout. This case is very interesting in completing the information gaiaedby this feeding experiment. No. 348, which had been fed with sodium car- bonate, besides being deprived of food, died three days after the ingest- ion of the culture. No. 350, which was simply starved, died ten days thereafter, while No. 342, which ate the culture without being previ- ously starved, was dying on the thirty-fourth day. These results show that infection may occur by way of the digestive system, provided the destructive action of gastric digestion be pre- 109 veuiC'd, lis was done by .stiirviiij;" and b^' the use of an alkaline car- bonate. They also indicate how purely local this destructive action maybe. Gelatine cultures from these animals showed that the internal organs contained but very few bacteria. So few were they in fact that the microscope alone could not have demonstrated their presence in the spleen. In addition to the cases given, equally positive results were obtained at four different times by the feeding- of pure cultures. Some of these results have been mentioned in otherplaccs (see page 207 of the Keportof Bureau of Animal Industrj' for 1885). It was also found that small quantities up to 100 cubic centimeters (^ pint) may be fed to moi^t pigs without obtaining any fatal results. Sometimes the fed animal becomes very sick, but recovers; sometimes no disturbance whatever is pro- duced. These experiments pro\e conclusively the causal relation between the bacilli of hog cholera and the disease so called. They show that pigs fed with nothing but sterile beef infusion, to whicli the minutest speok of growth from a hog cholera culture was added and in which the bacilli thus introduced were allowed to multiply ibr one or more days, were destroyed by a disease identical with hog cholera, but far more rapid in its course and more severe in its manifestations. SUBCUTANEOUS INOCULATION. Subcutaneous inoculation with hog cholera bacilli fiom cultures is successful in only a small percentage of cases, except when these germs are unusually virulerit. In the report for 1885 several cases of success fid inoculation are given, among which the following deserve to be briefly quoted: NovcDihcr 27, 1885. — Two pigs (Nos. 112, 114) were inoculated sub- cutaneously into the thigh with ,'3 cubic centimeters each of a jnire liquid culture. No. 114 died nine days after inoculation. The superficial ingui- nal glands were swollen, with hemorrhagic points in medulla. Spleen en- larged, dark. Extravasations on auricular appendages of heart. Lungs cedematous; bronchial glands enlarged, dark red throughout (hemor- rhagic). Glands of abdomen in general hemorrhagic, except those of mesentery ; petecchite under serosa of c;ecum. Kidneys with glomeruli appearing as blood-red points, the entire organ congested. Mucosa of fundus of stomach, lowest portion of ileum, and of the ca'cum and colon deeply reddened with slight extravasation. Cover-glass preparations as well as cultivations in gelatine and beef infusion revealed hog cholera bacilli, and these only. No. 112 died on the 15th day. Diairhea appeared two days before death. The lesions in this animal resembled those of No. J 14, with the ibllowing differences: Spleen very large, dark, friable. Kidneys less congested. Lungs with minute hemorrhages throughout the paren- chyma. Ecchymoses beneath the endocardium of left ventricle. Lym- phatics and digestive tract even more congested and hemorrhagic than in No. 114. no The success of tbese inoculations among numcrou , failures in subse- queut trials must be ascribed to the exceptionally virulent disease of that year, for noi cases have been observed since which died so sud- denly and i^reseuted such severe hemorrhagic lesions of the various vital organs. The following experiments, made with blood taken from the heart of swine affected with hog cholera and killed for the purpose, are taken from the report for 188G : September 10. — A pig dying with the disease was killed, the heart care- fully exposed, and the blood drawn with a disinfected hypodermic syringe. ISTos. 329 and 333 received subcutaneously 5 cubic centimeters each, one-half in each thigh. ]^o. 329 in a few days lost its appetite, be- came weak and stupid. Found dead October /i. Slight local swelling at the points of inoculation ; superficial iuguinals greatly enlarged; hypo- static congestion of lungs ; complete necrosis of mucous membrane in cjecum; large scattered ulcers in colon, showing as whitish patches on serous surface and encircled by a crown of enlarged blood vessels ; bac- teria in spleen. No. 333. Slightly ill for a time; fully recovered ; died December 2, with iro other lesions than engorgement of liver; no signsof former ul- ceration. A second experiment was made in the same way. October 13. — Nos. 324 and 325 inoculated as in the preceding experi- ment, 10 cubic centimeters of blood being used for each animal. No. 324 was found dead November 1, after being off feed for a time ; deeply red- dened skin over caudal half of abdomen; sui)crlicial lymphatics ex- tremely hirge and serously infiltrated; on section, hemorrhagic points; at ])oint of inoculation the connective tissue is infiltrated ; 50 to 75 cubic centimeters clear amber serum in abdominal cavity ; i)ai)ill;e of kidneys deei)ly reddened ; slight congestion, but no ulceration in large intestine; lymphatics in general moderately tumefied and congested. No. 325 found dead October 29; reddening of skin as in 324; ex- travasation in connective tissue; spleen greatly enlarged, purplish; lymphatics of thorax and abdomen purplish — enlarged; petecchije on section of kidney and pelvis, also over entire surface of epicardium ; lung tissue mottled both on surface and on section with purple spots, due to blood extravasation into alveoli, so that it scarcely tloats ; mucous and serous surface of small intestine dotted with jietecchiie ; small hem- orrhages on the surface of the mucous membrane and into the submu- cous tissue of the caecum and upper colon; ulceration beginning. On first thought we might be inclined to attribute these successful lesults to a greater virulence of the germs in the injected blood. This >iew needs further confirmation, however. The injected blood coagu- lating in the connective tissue contains in it the bacteria, which are not only protected from the aggression of cellular elements, but have actu- ally a store of nourishment upon which they may live and nudtii)ly. No such advantages are presented to bacteria suspended in liquids which are readily absorbed, leaving them to the mercy of the tissues surrounding them. The local reaction in the above animals was very insignificant compared with that produced by liquid cultures. In order Ill to come to any conclusion it would be desirable to add a few bacteria from cultures to fresh blood, and observe tlic relative virulence by sub- cutaneous inoculation. Elsewhere in this volume will he found a small number of successful inoculations with pure liquid cultures among a large number of unsuc- cessful ones. The inoculations were made for the purpose of determin- ing whether they would confer immunity. In reading over these ex- periments it will also be seen that such injectious produce swellings varying from the size of a pea to a hen's egg. The tumor is developed in the subcutisaud consists of a yellowish white, tough tissue, breaking down in the center into a grumous mass alter a period of one or more months. In view of these facts we can not consider wounds or bites inflicted on the surface of the body a means of infection, excepting, perhaps, in epizootics of extieme virulence. Nor can we ascribe much influence to the stings of insects in inoculating the virus from one animal to another, as this would correspond to subcutaneous inoculations on a minute scale. Flies may, however, infect food in various ways, to be dwelt upon in subsequent pages. INTRA- VENOUS INOCULATION. The injection of hog-cholera virus (from the spleen of a pig examined near the city of Baltimore, Md.) into the circulation was tried but once, and this trial was successful in producing a hemorrhagic septicjemia such as we frequently encounter in outbreaks of the disease, and which proved fatal in less than three days. N'ovemher 12, 1888. — Pig No. 90, black and white, about five months old. The right crural vein was exposed by raising a triangular flap of skin over it after thoroughly disinfecting the latter with a one-fifth per cent, solution of mercuric chloride. Five cubic centimeters of a beef infusion peptone culture inoculated from an agar culture about a week old was injected into the exposed vein with a hypodermic syringe thoroughly dis- infected with 5 per cent, carbolic acid. The li(iuid culture was two days old when used. Two hours after the inoculation the temperature had risen from 103y F. to 107°. November 13 there was no swelling, but a slight serous oozing at the place of inoculation. The appetite was good. November 14, at 3 p. m., the temperature was lOTf. The animal was disinclined to move, although it came to eat in the morning and even- ing. November 15 it lay on its side quietly, with occasional kicking. Found dead at 4 p. m. Autopsy held immediately. General blush on skin of ventral aspect, snout, and lips. No swell- ing at the point of inoculation; slight blood extravasation. Spleen en- ormously enlarged, 14 inches long, 2 to 3 inches wide, and one-half to 1 inch thick, gorged with dark blood, and friable. Superficial in- guinals enlarged, (edematous; on section diffuse pale red spots; cortex congested. Bronchial and renal glands enlarged, partly hemorrhagic, gastric glands hemorrhagic throughout substance. The blood is thick, dark colored, coagulation slight, even after several hours' exposure to the air. Several petecchia^. on epicardium of right auricle. Kight side of heart distended with blood: in it a small Avhite clot. Left side 112 coutrauted, empty. Liiugs normal, cxceptiD bacilli produce quite uniformly disease of the lungs, as i)as i een assumed by other ob- 113 servers without adequate proof. In the uotes of tbe outbreak ^iveu on page 54, this subject lias been pretty thoroughly discussed in the light of evidence furnished by bacteriological tests. The results there reached may be briefly summarized that lung disease or pneumonia of a severe character is not often found in hog cholera. The slight broncho-pneu- monia frequently met with is most probably due to. catarrhal conditions and to the aspiration of foreign bodies. There is, however, this very dis- eased condition of the lungs which may favor infection through tliem. When there are present foci of broncho pneumonia, hog cholera bacteria inhaled may lodge there, multiply in the secretion of the smaller bronchi, and cause an extension of tlie disease not jwssible in healthy lungs. From there they may be coughed up and swallowed, carried into the large intestine, where they exert their most destructive activity. In this sense the lungs may become the entrance of the virus, but only when previously diseased. In the examination of such diseased lobules of the lungs, in the outbreak referred to, hog cholera bacteria were found in almost exery case. In these case« it is difficult to decide whether they entered the diseased lobule from without by way of the bronchi — i. e.f with the air inspired — or whether they were deposited there by the circulating blood. The question of the relation of lung disease to hog cholera has been (;omplicated by the existence of an infectious pneumonia in swine, which we have called swine plague. This disease, which will be treated of in a special jjublication, appears over a large part of our country at times in virulent ei)izootics. It is caused by a widely distribute! septic organism, and ai)pears occasionally in swine suffering from hog cholera. In a number of such cases both disease germs have been obtained from the same animal. We do not exclude infection through the lungs as improbable in hog cholera, especially in epizootics characterized by more than usual viru- lence. At the same time long experience at the experiment station has shown that swine do not become infected in pens only a few hundred feet away from i)ens full of sick and dying animals. Currents of air can thus have but little power in distributing germs capable of inducing the disease. SOME OBSERVATIONS ON THE PATHOLOGICAL ACTION OF HOG- CHOLERA BACTERIA. We have frequently recurred to the fact that the intestinal tract seems to suffer more or less exclusively in hog cholera. The changes there produced belong chiefly to the necrotic and ulcerative' type, combined with a variable amount of neoplastic growth in tiie bottom of the ulcer. In connection with this work it has been impossible to nuike any ex- tended observations on the genesis of these ulcers owing to the exactions of other work. Whatever may be suggested here must be regarded simply in the light of inferences from lesions as they were observv^d post mortem. I06I2 H c- — 8 114 The ulcers are produced in most cases by a process beginning at the surface of the mucosa. This is shown very well by sections of ulcers in which only a portion of the tubular glands have been necrosed. What this process is must be left an open question. It seems very probable that the bacilli invade the tubules and blood vessels of the mucosa, by their rapid multiplication plug the latter, and cause a coagu- lation necrosis of the most superficial portion of the membrane. The various bacteria present in the intestine then complete the breaking down of the membrane, and an ulcer is formed. Ulcers may, however, be formed by bacteria carried thither by the blood, for ulcers are pres- ent in those animals upon which subcutaneous inoculation has been practiced (p. 110). In these cases the plugs or infectious emboli are situated probably in the submucosa. The resulting ulcer is deeper and more extensive. The formation of plugs or thrombi is confirmed by inoculations in rabbits (p. C9). The process of coagulation necrosis, as the result of plugs in the capillaries of the liver, may be seen in almost every case. Microscopic examiuation likewise reveals their growth in masses in the internal organs. The nature of the hemorrhagic ksions so frequently observed in hog cholera demands some attention. The rupture of minute and some- times larger blood vessels is no doubt due to the same process of throm- bosis and embolism in which the thrombi and emboli nuiy be made up more or less entirely of bacteria. Whether these i)lugs have a directly di'Structive action (necrosis) upon the delicate vascular wall so as to produce rupture and extravasation, as has been suggested in former reports, or whether the action is merely mechanical, or whether both causes are at work, it would be impossible to say. At* all events these hemorrhages are frequently the precursors of ulcers in the intestine, and in some cases the only lesions which were observed were hemor- rhages fiom large and small vessels. We may picture to ourselves the process, beginning, in most cases, with local ulceration in the large in- testine (cfEcum). The bacilli may be carried thence through injured vessels into other parts of the body, and to other portions of the iu- testine, where fresh ulcers may apx)ear; or the bacilli may be carried onward from the first ulcers to portions of the intestine lower down, where they again attack the mucous membrane. In many cases the quantity of virus introduced into the digestive tract is so great — as when pure cultures of hog cholera bacilli are fed — that destruction of the raucous membrane goes on at the same time throughout the csecum and colon, becoming less severe as the rectum is approached. The paralysis of the large intestine may cause extensive necrosis of the ileum. In these cases the action of the bacilli is purely superficial at first, penetrating deeper and finally reducing the entire wnil to a friable mass, greatly swollen by the infiltration of leucocytes. In such feeding experiments we may also observe gras deep red throughout; glomeruli visible as dark points. Lungs pale, not fully collapsed. Right heart filled with semi-coagulated blood. Liver gorged with blood. Mucosa of stomach intensely reddened, especially along fundus, and covered with a thick layer of tenacious mucus. JNIucous membrane of ileum similarly affected. Peyer's patches exceedingly 120 dark red, showing tlirougli serous coat. Wlien viewed from tlie mu- cous surface tbe elevated border gives each a slightly concave boat- shaped appearance. The colon also deeply congested, almost hemor- rhagic in patches, filled with a small quantity of serai-liquid feces. The rectum still lilled with consistent masses. The mesenteric glands con- gested. The feeding had thus produced a very severe inflammation of the digestive tract. The diagnosis was further confirmed by obtaining pure li(iuid cultures from the spleen, the liver, and blood from the heart. The bacteria were not snfhcieutly numerous in these organs to be detected by the microscope. To make sure that the carbonate of soda had no corrosive effect, another animal was treated precisely in the same way by starving and feeding a solution of the salt. ISfoill effects whatever were manifested. In order to test the specific pathogenic character of the bacillus obtained from this animal a large rabbit was inoculated subcutaneously with about oueeight cubic centimeters of a liquid culture from the blood. On the sixth day the rabbit was lying on its side; abdominal breathing very labored. It was found dead on the next day. Slight thickening of the subcutaneous tissue and fascia covering the thigh muscles at the point of inoculation. The muscular tissue covered with minute ecchymoses around the infiltrated patch. Small quantity of serum in the i^eritoneal cavity. Spleen very large, blackish, exceedingly friable, and crowded with bacteria. Liver enlarged; interlobular tissue pale; the entire parencliyma very soft and brittle. Dotting both surfaces of all the lobes are small, grayish-white patches, involving one, two, or three, larely more, acini, and bounded very sharply by the acini themselves. I'eculiar figures are thus formed, three contiguous ones giving the l)atch a clover leaf appearance. On section they are found to extend to the depth of one or several acini into the parenchyma. The great ma- jority of these masses of coagulation necrosis involve lobules ou or near the surface. Only a few are in the depths of the organ. When such a whitish mass is spread on a cover-glass and stained innumerable bac- teria of hog cholera make their appearance. The rest of the tissue is likewise crowded Avith them. Beneath the inrlmouary pleura are large ])urplish patches of extravasation, which ou section extend deeply into the parenchyma. The lung tissue is in general congested. Blood from the heart contained very few bacteria. No cultures were made. Maryland. — During September and October, 1888, an epizootic of hog cholera was started at the experiment station by a sick x>ig brought from near the city of Baltimore, Md. The hog cholera bacillus had been previously obtained from the spleens of two animals killed at Balti- more. At least twenty, which had been either simply exposed in pens or fed with the viscera of dead animals, saccumbed to the disease. In all cases pure cultures of the specific bacillus were obtained directly from the sj^leen. Its effect upon rabbits and mice, its appearance and mode of growth, did not differ from the bacillus as described in the fore- going pages, RELATION OF HOGr CHOLERA TO THE PUBLIC HEALTH. The importance of knowing whetber or not certain infectious animal liiseases have any deleterious influence upon human health, or are .the 121 direct cause of Imman disease, is not even second to the economic im- portance attacliing to aiiiaial diseases. There are some animal diseases, such as glanders, tuberculosis, anthrax, and rabies, which are directly communicable to man. This transmissibility was known before the si)ecific bacterial organisms of these diseases had been discovered. There are other animal diseases not proved to be transmissible to man, whose causes have only been definitely recognized within the past few years. As regards these it is quite pertinent to ask, in the light of l)resent knowledge, whether they have any relation to human diseases. Animal diseases when communicated to man may become so changed in character as to be unrecognizable. Hence we must determine whether the specific micro organisms of animal diseases are found in human dis- eases or not; in other words, whether the causes are identical. During the course of these investigations this problem has been constantly borne in mind. The question to be settled first has reference to the presence of hog cholera bacilli in human diseases. There are two mala- dies of mankind which resemble hog cholera in many respects— typhoid fever and dysentery. Typhoid fever is an infectious disease of man, prevalent throughout the civilized world, while hog cholera is known to exist only in North America and the British Isles, and during last year it has been identi- fied on the continent of Europe. Hence there could be no close relation- ship between the two diseases, for they would naturally occur together if they were identical. But there is another reason for their non iden- tity ; the uiicro-organisms which produce them are different. Thus the typhoid fever bacillus is a longer rod than the hog cholera bacillus, its movement in liquids is more sluggish and of a somewhat different char, acter. Its growth on boiled potato is almost pecnliar to itself. More- over, it has no pathogenic effect upon any animal thus far tried, and we know that the hog cholera bacillus is fatal to mice, rabbits, guinea. pigs, and pigeons after subcutaneous inoculation, and to pigs when fed to them. Hence there remains not the shadow of a doubt that genuine typhoid fever and hog cholera are distinct diseases. They do, however, belong to the same general class of infectious diseases. In both, infection very likely occurs chiefly through the food and drink. In both the lesions are ulcerative in character, located in the pig in the upper portion of the large intestine, in man in the lower portion of the small intestine. It is true the ulceration may be the secondary stage of processes primarily' diff"erent anatomically speaking, but we know as yet too little of the relative effect of irritants of the same kind, but of different intensity, to venture any positive statement. In both diseases the invasion of internal organs by the specific micro-or- ganisms takes place, so that they are readily obtained from the spleen. In both they appear in chimps or colonies in the capillaries. There is also a general resemblance of the two organisms, both as regards their appearance, motility and growth in various media when we compare 122 them with the bacteria of other infectious diseases in man and animals. We may tlierefore conclude that although these two diseases are en- tirely distinct there exists a close relationship between them as to the cause, the manner of infection, and the type of disease. Hog- cholera is allied to the disease or group of diseases known as dysentery even more closely than to typhoid fever. It resembles, per- ha ps, most nearly that form called epidemic dysentery. Of the causes of tliis disease very little is known. That the epidemic type is caused by microorganisms of some kind is now generally accepted, and it is also believed that there may be several distinct species of microorganisms which are capable of producing diphtheritic and ulcerative lesions of the large intestine.* Anatomically hog cholera and diphtheritic dys- entery are very much alike. The question whether hog cholera virus can ever produce a dysenteric afl'ection in man is not answered until we have learnt more of the causes of the latter disease. The danger, if any there be, of causing disease in man would only oc- cur upon farms where the opifortunity is afforded for infection of food and water by the discharge of diseased pigs. The preparation of pork by cooking is sufficient to destroy the bacilli if by any chance the flesh of diseased animals should get into the market. Experiments have shown that a temperature of 140° F. is sufficient for their certain de- struction. The temperature reached in boiling, roasting, etc., is of course mnch higher than this. In addition to these conclusions, which follow from the facts devel- oped by our experiments, it may be said that with the thousands of post-mortem examinations made by ourselves and other investigators, there has not been a single case where the operator became infected. In several instances it has been recorded that fresh wounds upon the hands have been covered with virulent material during the examinations without producing any appreciable effect. And through all the years that this disease has prevailed so extensively in the United States tbere has not been a case reported where it has been shown on good evidence to have been transmitted to the human species. Notwithstanding these facts, however, we should expect, with the prevailing carelessness in disposing of the carcasses of swine in many sections during such outbreaks, that there would be a more or less deleterious effect upon human health, not from the specific nature of the disease, but from the decomposing organic matter. Too often these carcasses are left to putrefy near dwellings, or are thrown into streams to contaminate them with decomposition products. Such practices are dangerous to the health of the community and should be prevented by the local sanitary officers. investigations of the Egyptian dysentery by Kocli a,utl Kartulis Lave shown that the cause is an organism helonging not to the class of bacteria, hut to the protozoa, and assuming the form of an amreba. This is ibund in hu-ge numbers in the ulcerated walls of the intestine. PREVENTION OF HOG CHOLERA. ISOLATION, DISINFECTION, AND CLEANLINESS AS PREYENTIYE MEAS- URES. It is frequently necessary to apply preventive measures before infec- tious diseases have actually appeared in a herd. The disease may have appeared on a neighboring farm, and the problem then arises : How can the infection be prevented from si)reading to other farms ? How can the surrounding farms keep the malady from their premises ? The sources and channels of infection are as follows, the most common and important being placed first : {(() Pigs purchased from infected herds, or coming in contact with those from infected farms, or running over grounds occupied by diseased sicine within two or three months. (b) Infected streams mag communicate the disease to herds below the source of infection. (c) Virus may be carried in feed, implements, and on the feet and cloth- ing of persons from infected herds and premises. {d) Winds, insects, birds {particularly buzzards), and various animals may transport hog cholera virus. {a) In regard to a, it may be said that no pigs should be purchased from any locality until one year after the death of the last case of chol- era. There are frequently near the end of an epizootic chronic cases which may live for three or four months without showing any distinc- tive signs of disease until they suddenly die. The post-mortem exam- ination usually reveals extensive ulceration of the large intestine. The disease may thus linger in a herd long after all danger has appar- ently subsided. By bringing any chronic cases in contact with hitherto unexposed healthy swine the disease may spring up anew, as a dying fire Avould when supplied with fresh fuel. Although our experiments have shown that the disease germs may all disappear from the soil in three or four months, the uncertainty of knowing whether there are any chronic cases continually adding fresh virus to the soil makes the period of one year not too long to avoid the introduction of unexposed pigs. It is advisable, in districts where hog cholera is very prevalent and is rarely absent for any length of time, for farmers to raise their own pigs and not trust to any animals from outside. In this way infection may be at least in part kept under control. When animals have been ob- tained from i)laces which are not above suspicion they should not be brought in contact with swine already on the place, but quarantined as 123 124 far as possible from them aud kept under careful observation for at least one mouth. (b) Perhaps the most potent agents in the distribution of hog cholera are streams. They may become infected with the specific germs when sick animals are permitted to go into them or when dead animals or any part of them aie thrown into the water. They may even multiply when the water is contaminated with fecal discharges or other organic matter. Experiments in the laboratory (p. 70) have demonstrated that hog cholera bacilli may remain alive in water for four months. Making all due allowance for external influences and competition with other bacteria in natural waters, we are forced to assume that they may live at least a montli in streams. This would be time enough to infect every herd along its course. (c) Hog cholera germs are not immediately destroyed by drying. Laboratory experiments show that they may retain their vitality from two to four months. Hence it is not difficult to see how a person walk- ing on infected ground and among infected animals may carry on his shoes and clothing dried germs of the disease to any neighboring herd. For the same reason hog cholera germs may be carried from infected grounds to others by fe^d, and by farming implements which have come in contact with infected ground. {il) There is no reason to suppose that currents of air have much in- fluence in spreading the disease. Observations at the experiment sta- tion of the Bureau have left no doubt that healthy pigs may be kept on the same farm with diseased ones without becoming infected, provided the infection is not carried in feed and implements, or on the shoes and clothing of persons from the sick to the healthy. Moreover the disease is an intestinal malady, and all evidence points to infection through the food rather than through the air inspired. The agency of flies and other insects is perhaps equally limited when infection is to be carried from one place to another. Our experiments show very well that the sting or bite of an insect is not sufficient to pro- duce the disease. It is possible, however, that they may carry the virus from one place to another in the same yard. This will be dis- cussed more fully under another head. The agency of buzzards in distributing the disease in the Southern States seems probable, although there is no positive proof. These birds will readily consume carcasses of dead swine. If the hog cholera germs are not destroyed by digestion it is reasonable to assume that the feces contain the living germs, which may cause the disease to break out at some distant place. Of course, the remedy would be to immediately destroy or bury dead animals. There is some reason to believe that rats, dogs, aud perhaps other small animals may carry the germs upon their feet or in their hair and thus infect premises. It is probable that the contagion is only rarely transported in this manner, but there are outbreaks the origin of which 125 it is difficult to exi)laiii otheiwise. We uuiy readily conceive, bear- ing in mind the facts enumerated above, bow sucli auimals might be- come contaminated with moist, semi-liquid, or liquid matters containing the germs, and that these substances drying upon the feet or hair would adhere for a considerable time. If an animal thus infected should go into uninfected lots occupied by swine and deposit there the smallest l^article of the germ containing material, either in liquids standing in the feeding troughs or in moist organic matters suitable for the multi- plication of the microbes, an outbreak of the greatest virulence might be set up. The number of conditions which must coincide for the spread of the disease in this way probably accounts for the comparative rare- ness of this kind of infection. Granted, tlien, no communication between infected and uninfected farms, there still remains the danger of infected watercourses, upon whicli it is impossible to lay too much emphasis. In fact, if the disease exists anywhere along a stream all farms below that point are liable to infection unless use of the water in any form whatever is given up dur- ing the season. By paying particular attention to these points, there is no doubt that the disease can be warded off, even when in the immediate neighbor- hood. Hog cholera is analogous to typhoid fever, dysentery, and Asiatic cholera in man in many particulars, and there is a quite unanimous opinion that these diseases are most commonly transmitted through drinking water. The same may be predicated of hog cholera, ajid the mysterious spreadof tliis plague will no doubt frequently be understood by examining the water courses. When the disease is in the neighborhood it has been customary with some to feed swine on some so-called " preventive" medicine. These arc frequently prepared or invented by individuals who Lave little, if any, knowledge of the action of medicines. The outcome is that the animals fed with these unknown compounds are not only not benefited, but their vitality is af;tually reduced, and when the disease appears it destroys the weakened animals much more easily. The writer has made post-mortem examinations of several animals in the West where such preliminary treatment was going on, and the peculiar changes of the internal, organs, not like any known disease, could only be referred to the action of such preparations. It must be remembered that there are few medicines which are not injurious or poisonous in large doses* They should not be used thus excepting under special conditions, and only given as recommended by those who have been trained to know the peculiar value and effect of drugs. The condition of the animals themselves is of great importance in favoring ur preventing infection. When pigs are fed with liquids in which the specific bacilli only are present, those that have been de- prived of food for some time previous take the disease, while those v;hose stomachs contain food that is undergoing digestion do not take it 126 readily. If, besidr.'s starving tlie animals, they are fed witli some alka- line solution, by which the alkalinity of the stomach is increased, the pa- thogenic effect is still more pronounced. Any disorder of digestion by winch the secretion of gastric juice is diminished or checked and the mucus is increased in quantity will increase the susceptibility of the animal to infection, because the alkalinity of the mucus mIU favor rather than destroy the virus. Any mode of feeding which produces constipation and over-distension of the large intestine is likely to favor the disease, as the virus is retained for a longer time. During epizootics, therefore, besides the preventive measures suggested, the animals should be carefully fed upon food which tends to keep the bowels open and the feces soft, and which does not interfere with normal digestion. When there is a suspicion that a herd has been infected, although the disease has not yet appeared, disinfection, and all the rules laid down' below (p. 130) should be carried out with great care, as if the dis- ease were actually present. When hog cholera has appeared in a herd or on a farm, precautions should be taken for two reasons: (1) To jirevent the virus from being carried to other farms and infect other herds. (2) To prevent the loss of the entire herd, or, if this is not possible, to stamp out the disease in such a way that the ground shall not infect healthy animals subse- quently. The rules under the first head should be prescribed by law to protect l)roperty frotn the consequences of the carelessness or the willfulness of those who refuse to take proper precautions. They may be summar- ized as follows : (a) The dead animals should be immediatehj disposed> of^ cither by burial or by burning^ or if ihey arc talcen to some rendering establishment their transportation should be gorerned by well-defined rules which will prevent the dissemination of virus on roads, in wagons, cars, etc. {b) Streams should be carefully protected from pollution. (c) No animals should be removed from any infected herd or locality to another free from the disease for at least six months after the last case of disease. {a) The proper disposal of dead animals is a matter of great impor- tance, for the bodies not only contain the germs of the disease, but the latter will multiply enormously during summer heat in the internal or- gans after life has been extinguished. Each dead body must therefore be regarded as a focus of the disease unless properly disposed of. It may be buried. In such case it must be so deep that no animal can get at it. It should be covered by a layer of powdered or slaked lime sev- eral inches thick, and the ground over the body likewise sprinkled with a thin layer of the same. If the carcasses are burnt, care should be taken that any parts not consumed are buried as directed. If they are carried away some distance to rendering establishments, at best a dan- gerous pocedure, employes of such establishnieiits should be compelled 127 to wrap arouiiu the carcasses impervious cloths wetted with a 2 per ceut. solution of carbolic acid, so as to protect the roads from the virulent drippings. [b] The danger from infected streams has already been mentioned at length. These must be protected by law iu such a way that no sick ani- mals should be allowed to go near them, and that no carcasses be thrown into them or deposited where drainage may carry the virus from the body into the water. Nor should the drainage from pens be permitted to flow into them. (c") Hogs are frequently affected with cholera of a mild form, which lasts for several months before some form of septic infection or degen- erative changes in the internal organs produce death ; hence it is im- portant to insist upon knowing when the last case of disease occurred. Since it hits been demonstrated that hog cholera germs may remain alive iu the soil from three to four mouths, this rule will not appear un- reasonable as a safeguard. These rules will be sufficient, if properly executed, to confine the disease within narrow limits. There is no doubt that hog cholera virus dies out over the greater part of our country after epizootics have swe[»t over it. We have no reason to believe that it can survive iu the soil from one end of the year to the other. It is, in fact, highly probable that it is transported and distributed from a few places where, for some reason, cases have occurred throughout the year and have thus kept the vii'us alive. There are no experiments on record which show that the hog cholera germ may be found in the soil and water independent of the disease. It has been looked for, but has never been found, ex- cepting in the body or discharges of diseased swine. In view of the fact that the disease can be kept under control, the legislatures of those States which suffer most severely from this plague should take steps to enact rules similar to those formulated above. The States of Kansas and Nebraska have on their statute-books laws of this character, which read as follows: AN ACT to prevent the spread of disease among swine. Be it enacted by the ler/islature of the Slate of Kansas, It is hereby made the duty of every person who owns or who has the control of any hog that has died of any dis- ease to bury or burn the same within twenty-four hours after such hog has died, and any person who knowingly fails or Refuses to comply with the provisions of this sec- tion shall be deemed guilty of a misdemeanor, and upon conviction thereof shall bo fiucd not exceeding one hundred dollars. Sec. 2. Whoever shall knowingly barter or sell any hog afflicted with any disease without giving full information concerning said disease sliall be deemed guilty of a misdemeanor, and upon conviction thereof shall bo fined not exceeding one hundred , and c, together with directions for their proper execution. The disease, spreading so easily and rapidly, requires great promptness of action and quite different rules from those which must be adopted iu the suppression of glanders or tuberculosis, for example. The difference is due to the nature of the specific microbe, so unlike those causing the two diseases mentioned. It is not strange that so little attention has been paid to the restric tion of this disease in the past, since legislators and boards of health and State veterinarians have had no scientific basis upon which to frame laws. Even now efforts are being made in varioas^ quarters to controvert or openly deny the accuracy of the investigations and re- sults obtained by the Bureau, and throw the whole subject back into the chaos iu which it was but a few years ago. This must have any thing but a salutary eifect upon those intrusted with the framing and execution of specific laws for the protection of domesticated animals. Having thus far dwelt upou the means which must be adopted to prevent the spread of the disease from one place to another, it becomes necessary to consider someof tlie measures that should be employed in checking it after it has once taken foothold in a herd. But how are we to recognize the disease? To answer this question it may be well to recai)itulate briefly some of the more important features of the mal- ady in as simple language as possible: It is quite common for the disease to announce itself by a few sudden deaths. The stricken animals may seem well a day, perhaps only a few hours, before death. In order to remove any doubts as to the precise nature of the disease, it is best to examine one or more of the animals before burying or burning them. This should be done in a secluded 129 place which pigs can not reacb, and the ground thoroughly disinfected, as will be described later. The disease in the sudden cases can be easily recognized. The spleen is, as a rule, ver^' black and enlarged. Spots of blood from the size of a i)in's head to a quarter inch or more will be seen in the fat under the skin, on the intestines, lungs, heart, and kidneys. The lymphatic glands are purplish instead of a pale pink. When the largo intestines are opened they are found covered with these dark spots of blood more or less uniformly and entirely. Often the contents are covered with clotted blood. Any or all of these may be considered as signs of the disease in its most virulent form. In many outbreaks the early cases do not succumb so rapidly. They grow weaker, lie down much of the time, eat but little, and usually have diarrhea. Most of such cases maj^ linger for weeks, meanwhile scattering the poison in the discharges. The disease may be recognized in these cases as soon as they are observed to act suspiciously, and there should be no delay in determining at once the nature of the disease. When the animal has been opened the large intestine should be carefully slit up and examined, beginning with the blind or upper end. There will be seen roundish, yellow or blackish spots, having an irregular, depressed, sometimes elevated surface. These spots correspond to dead portions of the mucous membrane, and they are frequently seen from the out- side as soon as the animal is opened. Sometimes the membrane has been entirely destroyed. (See also pp. 39-52.) In order to comprehend fully the reasons for the preventive measures suggested, let us briefly trace the various ways in which hog cholera bacteria may pass from a diseased or dead animal to a health^' one. Pigs may become directly infected by feeding on the carcasses of such as have died of the disease, or by eating food contaminated with the feces and urine of sick animals, or they may become indirectly infected by feeding upon material in which hog cholera bacteria are accidentally ])resent, and in which they have multiplied. This would include milk^ water, and perhaps most vegetables in a boiled condition. It has been pointed out in i:>receding pages that hog cholera bacteria multiply very abundantly in milk, especially in warm weather, that they remain alive in water for months, and that they multiply upon boiled potato. It has also been shown by an extended series of experiments (p. 80) that they may remain alive in the soil for from one to four mouths. The sources of infection are thus numerous enough. It has likewise been demonstrated that these disease germs will resist drying. Hence, dried discharges of the sick or the dried body of dead animals are still in- fectious. The channel of iufection is in most cases the food and drink. This has been frequently demonstrated and emphasized in these pages. The food, after leaving the stomach, passes in a liquid condition through the small intestine, so that this never seems filled; in fact, its only contents are a coating of semi-liquid matter over the mucous mem- 15G12 n c 9 130 braue. It pas^ses tbiougb the small intestine quite rapidly, but on reaching- the large intestine the undigested remains become more con- sistent, because the liquid is re-absorbed, and are kept here for some time. The bacteria, if not destroyed by the gastric juice, pass quickly through the small intestine, but in the large intestine they begin to multiply and attack the mucous membrane, which they destroy. Thus the feces or discharges of diseased pigs, wherever deposited, scatter larger or smaller quantities of the virus in this way, completing the circle of infection. In order to prevent the remaining healthy animals in an infected herd from takiug the disease the following measures are suggested as of importance, some or all of which may be carried out according to cir- cumstances : {a) Removal of still healthy animals to inclosed uninfected ground or pens, as far as possible from infected localities. (b) Destruction of all diseased animals. (c) Careful burial or burning of carcasses. (d) Repeated thorough disinfection of the infected premises. (c) Great cleanliness, both as to surroundings and as regards the food, to prevent its becoming infected. (rt) The importance of this measure need not bo insisted upon, after what has been stated of the various ways in which pigs may bo infected. The distance to which they may be removed will, of course, depend on circumstances. They should be kept so far away that there can be no means of communication, eitlier by direct contact, by drainage of the surface of the soil, or by gusts of wind. They should not be kept too closely confined, for if the disease should have attacked one or more and not manifested itself before removal, the infection would become general. Even after this precaution is taken, latent disease among such as are apparently healthy may infect the new grounds and the remain- ing healthy animals. This danger is increased by the fact that not un- frequently a number of animals become infected from the same source at the same time. Some will show symptoms very speedily ; in others the disease will remain latent for a longer time. Under such circum- stances it is impossible to properly isolate the well from the sick. Then there is the difficulty of preventing the well animals from carrying the virus on the skin and feet into their new quarters. These drawbacks may be in part overcome by very promjit action when the first signs of disease appear in a herd, before the virus has had an opportunity of being scattered about. The bodies of those to be removed may be fairly well disinfected by pouring over them a 2 per cent, solution of carbolic acid, and forcing them to walk through such a solution. (b) This measure is recommended to prevent the further spread of the virus by the diseased animals. In view of the fact that few re- cover, that even these few are stunted and of little value, that there is no reliable means of treatment which will eventually cure, destruction of 131 all sick aiiiimils is tlie simplest uiul most economical inocedure in the end. ((•) The (lisi)()sal of carcasses has alrea'iy been discnssed (i). ll*8). This very important measure should never be lost sight of. {(1) Among the various disinfectants which can be recommended are the following: No. 1. Slaked or unslaked lime, used both as a powder and as slaked lime, containing about 5 to 10 per cent, of dry lime (from i to 1 pound of lime to a gallon of water). iSTo. 2. Crude carbolic acid, i^repared by adding to the crude carbolic acid obtainable from druggists at about 90 cents a gallon an equal quantity of ordinary sulphuric acid. This mixture is to be carefully added to water in the i)roportion of 2 ounces to 1 gallon of water, about ]^ per cent. A'olume (see p. 91). iSTo. 3. A 1 per cent, solution (volume) of ordinary sulphuric acid (^ ounces of the acid to 1 gallon of water). No. 4. A 2 per cent, solution of pure carbolic acid. This is prepared by heating the crystals slightl}' until they melt and adding the resulting liquid to hot water, in the proportion of 1,^ ounces to half a gallon of water. (A pound of carbolic acid, crystallized, retails at 55 cents.) No. 5. Boiling water. The careful laboratory experiments with these disinfectants, upon which their practical application is based, are given on p. 87. We shall confine ourselves in this place to a description of their employment. Disinfectants are substances which, in solutions of a certain strength, are capable of destroying disease germs. Consequently they should be applied wherever the disease germs are supposed to be. In case of hog cholera they are attached to the sides and floorings of pens and to the various utensils used in cleaning them. They arc mixed with the earth over which the diseased animals have run, or in the water which they have frequented. In the report of the Department for 188G the use of mercuric chloride (corrosive sublimate) was recommended, as it is a pow- erful disinfectant. Since that time other disinfectants have been tested which are equally cheap and easily procurable. The main objection to mercuric chloride is its extremely poisonous character, which makes it undesirable to deal with. This substance has, therefore, in spite of its powerful germicide properties, been thrown out of our list of available disinfectants. The wood- work of pens, fences, flooring, etc , is best disinfected by using upon it, with a broom, solution No. 2 until thoroughly wet. In preparing this solution it should be stated that the mixing must be done in a glass bottle or jar and the mixture poured slowly into the proper amount of water in a wooden pail. This should be rinsed out after using to jirevent the acid from slowly destroying the iron hoops. Whenever No. 2 is not obtainable No. 3, which seems to be equally efficient, may be used in its place. 132 Lime is a very efficient disinfectaut for hog cholera. Experiments have shown (p. 93) that a solution containing only .02 per cent, will de- stroy the bacteria. When much organic matter is present, as nuich as .5 per cent, to 1 per cent, may be necessary. We recommend the pro- portions given under No. 1, which give from 10 to 20 times the strength required. The resulting liquid is not too thick to be easily manipulated It may be used on wood-work as a whitewash, and it may be spread as a thin layer over the soil which has been infected. The 2 per cent, solution of pure carbolic acid should be used when- ever No. 2 ma3^ act injuriously by virtue of the sulphuric acid which it contains. In general we recommend the use of No. 2 or No. 3 as often as it maj^ heem necessary. It should be dashed upon the infected pens, troughs, tools, and over the infected soil. Wheu there is no objection to lime this may be used on the soil, as it is equally efficient. The discharges should be covered with powdered or slaked lime, and this should be thrown in abundance into pools or wherever water stagnates. In the case of troughs for feed, iron tools, etc., which are liable to injury, the disinfectaiit should be washed away with boiling water if this is at hand. Boiling "water will destroy hog cholera germs by simple contact, and the disinfection will thus be made more complete. Shoes may be dis- infected b.\ rubbing them with solution No. 4. It must be carefully borne in mind that no manure from sick i)igs should be removed until it has been treated with disinfectants. The cleaning must be done after disinfection and not before, to prevent the dissemination of living virus. The agency of mice and rats in transporting virus will dej)end upon the promptness and thoroughness with which disinfection and cleanli- ness are practiced. Mice are more dangerous than rats, in so far as they may take the disease by feeding (p. 72). Flies can cnly carry such small quantities of the virus that they are not likely to prove dan- gerous if disinfection and cleaning of feed troughs are attended to. If these measures are carefully carried out, the disease may either be checked or else mild cases only will appear, owing to the small quantity of poison which the animals are likely to consume with the food. The epizootic may be terminated by the destruction of most of the herd. This unfortunately is usually the case. What x)recautions must be taken to prevent subsequent outbreaks'? If only a few animals remain, it is best to slaughter thehij they are likely to suffer with the disease in a mild form and continue to infect the premises. If no more animals remain, there should be a tinal thorough disinfection and subsequent cleaning of the whole exposed teriitory, including every nook or corner where the disease has existed. This should be done with solution No. 2 or No. 3 as directed, used as freely as possible. After one or two days the ground may be covered with a thin layer, one eighth inch or more, of slaked lime in the strength 133 above given and left undisturbed. If there is no objection to wliitewasb, tbir, may be applied to infected woodwork as an additional safeguard. Even after this thorough treatmeut, it is best not to place any fresh pigs on the premises for at least four months after the final disinfection. When animals still remain that have been exposed and have not taken the disease, no fresh animals should be introduced for at least six mouths after the termination of the outbreak. The disinfection must have been equally thorough. After all this trouble has been taken there is still remaining the dan- ger of a fresh introduction of the disease, and we would therefore again call attention to the rules laid down in tlie beginning of this chapter. These, after all, must be considered as most important. It is much easier to keep the disease away than to eradicate it after it has been intro- duced, without great loss of time and money. We would also suggest that in those regions where the danger from hog cholera epizootics is always present, the methods of keeping hogs be simplified in such a way that disinfection may be practiced without too much labor and un- certainty as to the results. It is only necessary to visit a few farms to be convinced of the difficulty that may be met with in endeavoring to eradicate the disease. The hogs are allowed to stray into the most out of the-way places when sick instead of being kept in inclosures of definite form and size, which are readily nccessiblo. The poison is thus scattered in such a wa^' as to make disinfection impossible. It is cer- tainly not necessary in raising pigs to allow them to stray into arbors, behind hedges, hide themselves under barns and outhouses. In some farms which we have visited, and which were said to have hog diseases most of tlie year, there seemed to be no places about the house or gar- den where pigs did not go. Under such circumstances disinfection is is quite impossible. The pens and other wooden structures, fences, etc., are also apt to be in a very dilapidated condition, so that cleaning is very much complicated. Even under such circumstances the germs will finally perish without disinfection if enough time be given, since they gradually die in the soil and water, as our experiments have shown. A period of from six to nine months after all animals have been removed will be, in general, sufficient to purify the soil of these disease germs. In fact the natural disinfection is very probably accomplished in many cases in from three to four months, but it would not be safe to rely upon this. TREATMENT OF HOG CHOLERA. Upon tbio subject very little sboiild be said, for the reason tbat dis eased animals are a source of poison aud a menace to bealtby animals, and sbould be destroyed. Moreover treatment is exceedingly unsatis- factory, as tbe disease either terminates fatally, whatever remedies are used, or generally makes the animal useless if it sbould recover. We therefore urgently recommend slaughter of the sick aud thorough dis- infection as the safest and most economical treatment in the end. Treatment, however, is resorted to by a large number of owners of swine. Tbe number of specifics, so-called, which are being advertised is legion. We have tried some of the best recommended and found them of no avail. ISTor is there any "specific" known in the range of veter- inary or human medicine that will cure diphtheritic and ulcerative dis- ease of the large bowels except time, combined with ciirefiil dieting, rest, and a few palliatives to relieve pain. It is impossible to carry out this treatment on swine. The success frequently reported with sp^v cities iu hog cholera are very probabl3' due to the fact that the tieat- mentis usually adopted in mild forms of disease of a different nature which is mistaken for cholera, or when the acute outbreak is over and the plague has assumed a chronic character. The affected swine linger for a time with very slight symptoms of disease, and this change is credited to tlie "specific" employed. Remembering that the severest injury is done to the walls of the large intestines in this disease, we regarded it important to determine what medicine would give a prompt ami copious evacuation of the bowels in the very beginning of the dis- ease. Various medicines wtre tried by Dr. Kilborne, at the Experiment Station, among others the following: (1) Calomel and jalap.—Fehruixry 20, 1888. To No. 4G3, 30 grains calomel ; to Xo. 407, 23 grains jalap; to No. 4(38, 30 grains each of cal- omel and jalap. February 21. Same dose given again to Nos. 403 aud 408; no result. (2) Calomel. — March 7. To Nos. 441 and 442, each one dram of dry calomel. March 8. To 441 same dose mixed with castor oil; to 442 about li drams with castor-oil. No. 441 was freely purged after second dose, continuing for twenty to thirty-six hours. No.- 442 was freely purged after sixteen hours, continuing sixteen to twenty hour-j, when it died. At autopsy were found intense intiammation of stomach, super- ficial necrosis of the mucosa of large intestine with deep reddening resembling hog cholera. No bacteria found in cultures Irom spleen. These changes were no doubt due to the calomel. 135 136 (3) Calomel. — March 8. Nos. 403 and 4G8 received each one dram Coloniel in 2 drams castor-oil. No. 408 was purged freely in twenty hours, continuing- thirty six hours. No. 403 was purged in sixteen hours and made ill for several days. (4) Epsom salts. — Nos. 403 and 405 (w^eight 50 pounds) received each 1 ounce. Bowels slightly relaxed for one or two passages. Nos. 339 and 377 (weight 50 jiounds) received each 2 ounces in water. No. 339 Avas purged and made slightly ill. No effect on 377. (5) Barhadoes aloes. — Nos. 402 and 404 (weight 50 pounds) receiv^ed one-half dram each; no effect. Nos. 372 and 380 (weight 05 i:)Ounds) received each 2 drams, mixed in molasses ; no effect. The same ani- mals, five days later, received each 4 drams with molasses; no effect, except discoloration of feces. (0) Castor-oil and turpentine. — Nos. 387 and 388 (weight 50 to GO pounds) received each If, ounces castor-oil and one sixth ounce turpen- tine ; no effect. No 387 received, five days later, 2^ ounces oil and one- sixth ounce turpentine. No. 388 received, five days later, 2^^ ounces oil and one-third ounce turpentine; no effect. (7) Linseed-oil and turpentine. — Nos. 383 and 399 (weight 50 to 60 pounds) received each 2i ounces oil and one sixth ounce turpentine ; no effect. No. 383 received, five days later, 4 ounces oil and one-sixth ounce turpentine. No. 399 received five days later, 4 ounces oil and one- third ounce turpentine. Both were made sick for a day or two. No catharsis. These trials show how difficult it is to cause movement of the large bowels in swine, and they also suggest that this very sluggishness may make them susceptible to inflammations and ulcerations such as we find in nog cholera and frequently in swine plague. It was our intention to obtain a cathartic which would freely purge without causing any inflammation or irritation of the large intestine. Of those tried, calomel is the only available one. This must be carefully given, as it may produce the very inflammations which it is designed to check, and destroy life, as was acttmlly done in experiment 2. Concerning calomel EUenberger* says: Calomel (in combinatiou with castor-oil) is especially serviceable with swine; with larger animaLs Avheu the cont(!nls of the intestinal canal are to be disinfected, and in inflaminatory fevers. It shonhl be given to ruminants with the greatest cantion. It\vas our purpose to try calomel after having made these trials upon healthy aninnils, when the disease died out at the Experiment Station, and further investigations had to be postponed. If the large intestine has been promptly evacuated the next important step is to give only that food which leaves but little irritating waste to pass into the large bowel, sucli as milk and gruels. In short, it is best to use only boiled or scalded food so as to help the process of digestion as much as possible. It may be necessary to repeat the dose of calo- mel after a few daj^s. As to this mode of treatment our experience is not sufficient to warrant any positive statements, and it is simply sug- gested to those who wish to run the risk of treating this disease. * Lehrhiich d. aUtjemdiieii Tlierapie d. Ha used iigeth here, indf), p. 676. 137 There is another line of preventive and cnrative treatment which may prove valuable in the future, namely, the feeding of substances with the daily food which, while not injurious to the animal itself, may keep in check the multiplication of the virus in the intestine by an antiseptic action. It is very imi)ortant, however, to bear in mind that a large number of those medicines which act as disinfectants and antiseptics are likewise injurious or even poisonous to the animal itself. A too abundant feeding of such material, while it may reduce the mortality and lessen the severity of the di.'^ease in the sick, is liable to cause in jury to liver, kidneys, and other vital organs, whereby the nutrition of the animal may be permanently injured. Such medicines, when care- lessly given to healthy animals as ])reventives, may irritate the large bowel sufficiently to reduce its vitality and power of resistance when the disease actually appears. The proper medicine to feed must therefore be selected with care, and we trust that experiments to this effect may be carried on at the Experiment Station at an early date. There is still another line of treatment which demands attention, namely, the introduction of a sufficient amount of some disinfectant into the body to be absorbed and thus to make the whole body oppose the multiplication of bacteria. Koch tried this method by injecting mercuric chloride into guinea-pigs and afterwards inoculating them with anthrax bacilli. The animals all took the disease and died. At the laboratory of the Bureau mercuric iodide, a still more power- ful disinfectant, was tried upon rabbits, A solution was prepared containing .001 gram mercuric iodide and .002 gram potassic iodide in a cubic centimeter. Of this .5 cubic centi- meter was injected beneath the skin of the back of four rabbits (Nos. 1, 2, 3, 4) for eight successive days. On the third day Nos. 1, 2, 3, and a fresh rabbit (check\ No. 5, received hypodermically into the inner sur- face of the thigh ^ cubic centimeter of liquid containing one millionth (Hibic centimeter of a beef infusion culture of hog cholera bacteria about one day old. All the inoculated rabbits died, the dates being given in the ai)pended table. Rabbit No. 4, which had received the iodide only, to observe any ])oisonous etteet, remained well. The lesions were those of hog cholera, and the specific bacteria were present in the spleen. The total amount of the iodide given was .004 gram, about jL grain. 'So.* .5 cubic centimeter of f'r, per cent, luercuiic iodide daily. Inoculated with one-mil- lionth cubic centimeter culture bog cholera bac- teria. Ilemiirk.s. 1 1 2 3 4 June 22 to 29, inclusive. .... do June 2t ...do 1 Died June 30. Died July 3. Died July G. Died July 3. ...do . . do ...do .do * Wf'isrliin;; oai'li :ibout 2 pouiid-s. 138 At the same time healthy pigs were fed with the same substance in minute doses, to observe any toxic effect that might appear. These exper- iments were likewise interrupted in tlieir application by the disappear- ance of the disease at the beginning of the year. While we therefore recommend in general the use of a purgative, such as calomel, in the beginning of the disease, and careful feeding subsequently, we have as yet no actual experimental evidence that such treatment will be of any avail, owing to the frequent interruptions of the work. EXPERIMENTS ON THE PREVENTION OF HOG CHOLERA BY INOCULATION. DiiriiJi;' the piust six or seven years tbe atteutiou of tbe world has been centered upon the brilliant experiments of Pasteur in tbe line of preventive inoculation for animal diseases. Many others have since then followed his footsteps witli variable success. Among those dis- eases for wliich preventive inoculation is more or less in vogue in some European countries, especially in France, are anthrax among cattle and sheep, charhon sympfomatiquc, afiecting the same animals and perhaps identical with the disease known as bhick quarter or black leg in this country. This is not the place for discussing the absolute value of vac- cination in these diseases, nor to point out the reasons why they are not regarded of much value by scientists of Germany and other States. SufBce it to say that the Bureau has devoted a largo amount of time in testing all the available methods of attenuating hog cholera virus for vaccinal use, to determine whether any vaccine could be placed at the disjiosal of the public that might prevent the enoimous losses entailed each year by this dreaded germ disease. In the following pages most of the work done (chiefly during the winter and spring of 1880) is briefly r('i)roduced Inocuhitions of small doses of strong virus in the form of liquid cultures was first resorted to, because it had been observed that i)igs rarely take the disease when culture liquid in such quantities is injected directly under the skin. We reasoned that if injections of suuill doses do not cause the disease, why may the}" not prove effective in preventing natu- ral infection? The cultures were not therefore attenuated, as Pasteur has done, with anthrax, because the step was deemed uunecessarj'. A lot of animals were at first inoculated twice with very small quan- tities, the period between the two inoculations being about two weeks. This time was sufBcient to reveal any disease which might Lave been induced by the inoculations. Two weeks after the second inoculation the animal was infected either by allowing it to feed upon the internal organs of pigs which had died of the disease or by exposing it to the sick and dying in an infected pen. It was soon found that the inocu- lations were by no means prot ctive, in whatever way the virus entered 140 the system, for subsequent feeding usually luoduced cases of the most acute character and ^Yith the most severe and extensive lesions. The doses of inoculated cultures Avere gradually increased in quantity with- out yielding any better results. Of a large number of animals sub- jected to inoculation only five took the disease unmistakably as a con- sequence of the operation. The experiments, iucluding tables and poHt-mortem notes, are given in extenso as they were made. In reading them over it will be uoticed that the virus was cultivated chietiy in liquid media, and the solid media, more particularly nutritive gelatine, were only employed to test the i)urity of the cultures. When- ever these cultures were used for inoculations they were previously tested on gelatine plates by drawing a i)latinuni wire, dipped into the culture, through the gelatine layer two or three times before the gela- tine had become solid. Among the hundreds of cultures thus tested in the space of several months not one was found impure. Series of cult- ures extending uj) to the tenth generation were usually carried on by inoculating fresh tubes each day. The last culture tested as describetl above gave precisely the same colonies as the first in all the series thus far prepared. The culture-tube, described in the First Annual Eeport of the Bureau, was used almost exclusively for these cultures in liquid media. The advantages and accessibility of cultures in liquids for l)urj)oses of inoculation, the readiness and ease with which quantities or doses may be determined, finally, certain characteristics of growth in liquids, place this nsethod on a level with, if not above, that of solid cultures for experimental purposes. For diagnostic purposes, solid media are to-day a shw qua non of bacteriological work. Experiment 1. — Pigs Xos. 152, 1G7, 1G8, and 175 were inoculated with pure cultures in beef-infusion peptone as follows: On January 23, one drop of the seventh culture, derived from the spleen of pig No. 114; on Februarys, with one eighth cubic centimeter from a culture derived Irom a guinea i)ig. Both cultures were ddutcd in sterile normal salt solu- tion in such a way that 1 cubic ceutimeter of fluid was injected each time. Theinneraspectof the thigh near Pouparl'sligameut was chosen, and the iiqnid was introduced beneath the skin into the subcutaneous tissue with a hypodermic syringe. There was no perceptible swelling at the site of either inoculation, excepting in No. 175, in which there were two tunu^rs, each the size of a walnut, at the seat of the first inoculation. In order to test the extent of the immunity which these inoculations might have conferred, feeding the viscera of pigs which had succumbed to hog cholera was resorted to, the animals being transferred to the large in- fected ])eu for this puri)ose. Nos. 1G8 and 175 were fed in this way March 5, and two animals not inoculated (Nos. 158 and 180) were fed with them. All four died; the two vaccinated animals in about twenty days, the others in about fifteen days after feeding. March 13, Nos. 152 and 107 were fed with two check animals, Nos. 176 and 190. These four also died of hog cholera; the two vaccinated ones averaging twenty days, the others eleven days after feeding. The inoculation may be said to have simply retarded death from five to nine days. A table 141 giving- a summary of those facts is appemlcd, togetber with a brief descriptiou of tha j^ost mortem appearances: Ko. January 23. Fed with hoo;. i'"(l)niar.v 8. cholera vi.s Cera. Died. Number of d.ay.s after feeding. 152 1C7 168 175 158 189 17(j 190 Drops. 1 1 1 1 c. c. i h i Mar. 13 Mar. 13 Mar. 5 Mar. 5 Apr. 3 Apr. 1 Mar. 28 Mar. 22 M.Tr. 91 21 19 23 17 10 H 10 12 Mar. 5 j Mar. 19.... Mar. 13 t Mar. 23 Mar. 13 \ Mar. '>.'>. . . . Auti>2)sy notes. — Xo. 152. Skin of limbs and abdomen dotted with purple spots; on abdomen, general reddening. Points of extrava.sation and ecchymosed spots throughout the subcutaneous connective and fatty tissue and on gastro-splenic omentum. Superticial inguinal glands greatly enlarged and congested. Spleen enlarged, filled with l)lood, and very soft. Petecchise on epicardiura. Numerous lobules of the lungs collapsed. Glomeruli of kidneys ajtpear as deep red petecchi^B. In ciecnm and upper portion of colon extensive and deep ulcers, A few in the ileum near the valve. The mucosa of the stomach, small and large intestine, thickly covered with dark red points or petecchia'. JS^o. 1G7. Dying, and hence killed by a blow on the head. Spleen swol- len, friable; epicardium dotted with points and spots of extravasation. In lungs a few collapsed lobules. Lymphatic glands generally very deeply congested, similarly the mucous membrane of fundus of stomach and the kidneys. Large ulcers in caecum and upper portion of colon. ^NTo. 168. Subcutaneous and subperitoneal tissue contains numerous ecchymoses from one eighth to three-fourths inch in diameter. Spleen enlarged, gorged with blood, friable. Petecchia? on epicardium. Lungs not collapsed; its parenchyma contains numerous deepl^^- congested areas from one-eighth to one-half inch in diameter. Kidneys enlarged, with extravasations on surface and in parenchyma. Cortex of lym- phatics in general deeply congested. Extensive, almost continuous, ulceration of caecum, and upper portion of colon, in part blackish, the remainder of the large intestine being the seat of severe inflammation and extravasation. Mucous membrane of stomach similarly involved. No. 175. Subcutaneous tissue dotted with pale red spots. Tumor at the place of the first inoculation firm throughout, pale yellowish. Su- perticial inguinal glands, as well of those of thorax and abdomen, with purplish cortex. Spleen tissue still firm, dotted with numerous bright red i)oints, but slightly enlarged. Beneath the entire e])icardium and endocardium many extravasations. Ctecum and upper portion of colon extensively ulcerated. Serous surface of large intestine dotted with extravasations. No. 176, Slight reddening of skin and subcutaneous fatty tissue. Cortex of lymphatic glands in general deeply congested. Spleen much eidargcd and surface dotted with numerous bright red elevated jioints. A lew ])etccchi;Te on endocardium and epicardium. Lungs deeply con- gested throughout; kidneys likewise inflamed. Stomach slightly red- dened at fundus; small intestine also slightly congested. Serosa of large 142 intestine dotted with extriiviisatious. Tlie mucosa of caecum and small portion of colon one mass of necrosed tissue. Walls thickened. ^o, ISO. Exlensi\'e and dee}) reddeninj;' of skin of abdomen, throat, and limbs. Subcutaneous tissue oidy slightly reddened; spleen en- hiiiicd, gorged with blood, friable. Besides the general congestion of the lungs there are small darker areas, representing hemorrhagiclobuies. IJronchial glands and those along lesser curvature of stomach swollen and gorged with blood; the other lymphatics only moderately congested. Besides a small number of ulcers throughout the large intestine, the mucous membrane is deeply congested and dotted with occasional hemorrh;igic i)oints. Kidneys extensively inflamed ; on section the cor- tex shows extravasations. No. 190. Considerable reddening of the skin of abdomen and ventral aspect of limbs; very slight in subcutaneous tissue. Spleen greatly enlarged, dark ])urple; blood flows freely on cutting into it; very soft. Lungs contain regions of congestion and hepatizations, possibly due to the presence of a few lung worms. Lymphatic glands near stomach, tlie bronchial and superficial inguinal glands, deeply congested. Mu- cous membrane of stomach extensively congested; a large patch of extravasaiion in fundus; large intestine severely inflamed, with occa- sional extravtisalions; no ulcerations. The diagnosis of hog cholera was confirmed in every case by finding the specific bacillus in cover-glass preparations of splenic tissue and obtaining therefrom juire cultures in liquid media and in gelatine. Experiment 2. — In conjunction with the first series of inoculations, two pigs (iS^os. 149 and ICl) were inoculated at the same time, as follows; January 23, with 1 cubic centimeter of the seventh culture in beef-infu- sion i)eptone. No reaction at the place of inoculation in No. 149; a tumor as large as a marble in No. 161. On February 8 both received a second injection of 1 cubic centimeter. Two swellings as large as a chestnut at the place of the second inoculation in No. 149; in No. IGl also a considerable thickening was present. No. 149 was fed March 5 with four of the jueceding series; No. 101 on March 13 with the remainder of the preceding series and some to be subsequently spoken of. Both died of hog cholera. The accompanying table and brief autopsy notes explain themselves : No. Inoculation. Fed. Died. Daya after feeding. Jau. 23. Feb. 3. 149 ICl c. c. 1 1 c c. 1 1 Mar. 5 Mar. 13 Mar. 24 Apr. 14 19 32 No. 149. Slight reddening of the skin and subcutaneous connective tissue; the tumors produced by inoculation firm, pale yellowish, only one showing soitening within ; spleen considerably enlarged and full of blood; ascarides in gall bladder, which is ulcerated; mucous membrane along fundus of stomach intensely congested; the mucous membrane of ctecum and upper portion of colon one mass of ulcers; in the remain- der of colon they are isolated; kidneys con^rested. 143 No. IGl. Great ciiiaciatioii; si)leen eiilarj^eil aii\g. In IsTo. 115 a tumor as large as a marble was found at the seat of inoculation March 9. In No. 160 the tumor was elongated, about 2 inches long and three-eighths of an inch thick. No. 115 was fed with viscera taken from cases of hog cholera March 19. No. 160 was simply exposed to the disease by being transferred to the large infected j^en. No. 115 died April 8. No. 160 recovered and was well May 6. The detailed account of this experiment is appended : • Tel). 13. Date of feeding and exposure. Effect. Days after feeding. 115 IGO c. c. 1 1 Fed Mar. 19 Exposed Mar. 22 Died Apr. 8 . Kecovered . . 29 Post-mortem yiotes. — No. 115. Firm, i^ale yellow tumor at seat of in- oculation, encysted ; center undergoing softening. Spleen tumefied, very dark and friable. A few extravasations beneath serous coverings of heart. In cortex of kidneys numerous hemorrhagic points ; cystic degeneration of right kidney; advanced ulceration of ciecum and colon ; scattered petecchicie in mucosa of stomach and small intestine. No. 160. Was very low for a time, beginning with April 1. It was barely able to stand and its appetite was poor. It rapidly recovered, however, and was gaining flesh in May. Whether the animal was suffer- ing from hog cholera or from the l^clerostoma pinguicola (kidney worm), with which some of this lot were found affected, can not be said. In order to determine whether a single injection of a comjiaratively large quantity of culture liquid, while not inducing the disease, would protect against the disease itself, the following experiment was per- formed : Experiment 6. — Four pigs (Nos. 202, 204, 205, and 212) were inoculated April 2 with 1 J cubic centimeters of a seventh culture in beef infusion with 1 percent, peptone one day old. Four additional pigs (Nos. 206, 207, 208, 147 and 209) received but one cubic centimeter of the same culture. The re- maining four of the same lot (Nos. 203,210,211, and 213) were reserved as checks upon the experiment. Of these ISTos. 203 and 213 had a temperature of 106"^ F., and hence were suspected of disease. This suspicion was soon confirmed after they had been placed in a pen alone. Both had a severe diarrhea, one dying April 11, the other Ai^ril 13. The lesions were con- fined to the mucous membrane of the large intestine, which was dotted with numerous elevated lemon yellow tough masses a few lines across, sim- ulating ulcers. On close examination, however, this impression was dis- X)elled. These tough masses were easily removed hi toto from the mu- cosa, which ij)resented a slight depression without any loss of substance. They were evidently exudates from the mucosa (croupous ?). There were no bacteria in the blood or in a bit of spleen dropped into a culture tube. No development took place in either tube. Of those inoculated with 1^ cubic centimeters two died from the imme- diate effects of inoculation. No. 204 died in eleven days and No. 212 in seven days. In No.204 atough tumor had formed atthe point of inocula- tion on each side. The mucous membrane of the large intestine was com- pletely necrosed and the spleen enlarged. In No. 212 local swelling was present on one side. The stomach and large intestine were deeply con- gested, with points of commencing ulceration in the latter. In both ani- mals the bacillus of hog cholera was presentin cover-glass preparations of the spleen. Nos. 202 and 205 seemed to remain unaffected by the inoc- ulation. One month and a half later both were exposed to the disease in the large infected pen. A mouth later they were removed with oth- ers to a clean pen, after having apparently resisted infection. No. 202 was gradually wasting away, and died July 24, more than two months after exposure. In the large intestine were cicatrices of healed ulcers and such as were healing. The severest lesions were in the lungs. Both were adherent by means of bands to the costal pleura, and were exten- sively hepatized. No. 205 was alive and well August 15. Of the second lot, which had received 1 cubic centimeter of the same culture the results were nearly the same. Two succumbed to the inocula- tion, one died of infection, and a fourth survived. No. 208 died fifteen days after inoculation. Besides the inoculation swellings, enlarged and congested spleen, the mucous membrane of the largeintestine was covered with extensive deep ulcers, and the walls much thickened and softened. The corresponding lymphatics in the meso colon deep purple. No. 209 died in six days after inoculation. There was general congestion and extravasation of blood in the internal organs, involving the entire mu- cous membrane of the alimentary tract, especially the large intestine, the lymphatics and serous membranes, the spleen, and kidneys. Ulcera- tion had not yet begun. In both animals the spleen was crowded with bacteria and furnished pure cultures of the specific germ. Nos. 20G and 207 were not affected by the inoculation. They were exposed with the iirecedinglot, as indicated in the table. No. 207, after 148 appareutl^" resisting iufection in the infected pen for a month, diedJuly 18, after liaving been in a clean pen since June 21. The extensive ne- crosis of the mucous membrane of the caecum and upper portion of colon, with the absence of any acute inflammation elsewhere, gave evidence of a chronic case of hog cholera. No. 20G, though still alive, is emaciated. The two remaining check pigs, which were exposed with the preced- ing animals in the same infected pen, both died of hog cholera; No. 211 found dead June 21. The most marked changes were a small num- ber of ulcers on a pale mucous membrane scattered over the caecum and colon. No. 210 lived a month longer than its mate. The existence of hog cholera was demonstrated by a general necrosis of the mucous membrane of the CiBCuiu and an extensive pigmentation in the remain- der of the large in testine. The lungs were adherent in places and much congested. When we gather together the facts presented by this experiment we shall find a certain number of interesting c" ductions springing there- from. In the first place, we note the peculiarity of the intestinal lesions of the two animals which died from some unknown cause, presumably not hog cholera. We next point to an additional demonstration of the specific nature of the bacillus of hog cholera, for out of eight inoculated four died, and the age of the lesions corresponded well with the length of time elapsing between inoculation and death. Those animals which resisted the inoculation were in part protected, as two among four were still alive on August 17, and the remaining two died, probably from effects of the ulceration, months after exposure. No. Inoculattd April 2. Died from inocu- l;it ion. Exposure in infected peus. Kemoved from infected pens. Remarks. *202 204 1^ c. c. culture liquid. do April 13 May 18 June 21 Died July 4. 203 do ....do .. June 21 Alive August 17. 0]^9 do April 9 206 1 c. c. culturo liquid .. May 18 June 21 Alive Augu-st 11, but unthrifty. Died July 18. 207 .. do 203 do April 17 April 8 209 do t203 Died April 11, irom a )nie unknown dis- ease. Died Julv 21, of hog cholera. 1210 May 18 ...do .. Juno 21 1211 j Died Juue 21, of hog cliolera. 1213 DiiHl April 13, from sarao disease as No. 20.3. * These animals were one and a half months old at date of inoculation. 1 Checks. Experiment 7. — Having determined that even large doses of liquid cultures of the bacillus of hog cholera can be borne without produc- ing the disease in most cases, it was thought advisable to make two in- oculations of strong virus, a first one with a small quantity and a second with a large quantity. 149 First inoculation, April 21 : Xos. 214, 227, 223, and 222 received ^ cubic centimeter of a tbiid culture in beef inlusiou coutainiug 1 per cent, each of peptone and glucose. Tbe liquid was diluted with sterile salt solution, so as to make i cubic centimeter. It was injected, one- half beneath the skin of each thigh. After waiting two weeks, in order to determine whether the inoculation had not produced disease, a second injection was practiced May G, the thirteenth and fourteenth cultures of the same series being used for this purpose. The animals received 1, li, 2, and 2^ cubic centimeters of the culture li(piid, respectively. No untoward results following the injection of these large doses, they were transferred to the large infected pen May 25. A second lot (yos.22G, 228,215, and 229) were treated in precisely the same way and at the same time, excepting in receiving i cubic centi- meter for the first dose instead of 4- cubic centimeter. No. First inoculation, Apr. 21. Second inoculation, May U. Expos- uie in infected pen. Time of death. Days after first exposure. 214 227 223 232 226 228 215 229 *224 *225 c.c. i i i i i J i 4 c. c. 1 2 2i 1 n 2 2h May 25 ...do .... ...do .... ...do .... ...do .... ...do .... ...do.... ...do ... ...do .... July 1 June 27 July 2 July 1 July 3 July 13 July 30 June 27 Aug. 4 June 27 37 33 38 37 39 49 46 33 71 33 do ' Checks. No. 214, being in a dying condition July 1, was killed. In the cfEcum and colon were found very large, deep, blackish ulcers upon a pale mu- cosa. The case was evidently one of chronic hog cholera. A pure liquid culture of the hog cholera bacillus was obtained from the spleen. No. 2'J,7 died June 27. The lymphatic glands were deeply congested ; the mucosa of large intestine was generally pigmented and co\ere'itb strong virus. The reaction * Comi)t. rend. Acad, des Sciences March 21, 1881. *CentraJbl. f. Bakteriologie und I'arasitenlunde, 1888, i. 571. 167 168 after the vaccinal inoculation was very slight. Hog cliolera virus is destroyed by a fifteen to twenty minutes' exposure in a water-bath at 5S^ C. ; a momentary contact witli boiling water is sufficient to destroy it, so that Kitt's method is not applicable to it, but only to bacteriii which form spores. The following experiments were undertaken with a view to test the method of Pasteur on hog cholera bacilli, and to obtain, if possible, a vac- cine similar to that employed in the prevention of anthrax. Although only a preliminary step has been taken in this matter, and the promise of favorable results is not tiattering, we consider it best to publish the results thus far obtained. The first step in the process was to obtain, if possible, a cultivation which should prove harmless to rabbits. This was to be accomplished by placing tubes in a thermostat, kept at a certain fixed temperature as nearly as possible, and inoculating rabbits from time to time to deter- mine anjf diminution in the pathogejiic activity. April 9, 1888. — Four Salmon tubes of beef infusion peptone were in- oculated from an agar agar culture of hog cholera bacilli two weeks old and j)laced in a d'Arsonval thermostat, the internal temperature of which registered between 42° and 43° C. Two series of inoculations were made on rabbits, one from one of the original liquid cultures at different intervals, the other from a culture renewed at the end of every five days by inoculating a fresh tube. The result is most easily under stood by examining the following table: Agar culture. Apr. 19, rabbit Apr. 25, died. inoculated Apr. 30, rabbit. May 4, died. May 9, rabbit. May 18, died. Apr. 0, b. i. p. *(a). Apr. 14, b. i. p. (a,)- Apr. 19, b. i. p. (a,,). Apr. 24, b. i. p. (a^) Apr. 30, 1). i. p. (ai). May 4, b. i. p. (ar,; May 9, b. i. p. (an). Apr. 19, rabbit inoculated. Apr. 24, died. Apr. 30, rabbit. May 5, died. May 9, rabbit. May 10, died. Beef inlusiou phi.s 1 per cent, peptone. 169 The first inoculations were made April 10, with culture «, wliicli had been in the thermostat ten days, ar,d culture Both died May 4 and 5, respect- ively. Lesions the same as with the first pair. Two rabbits were inoculated May 9, one from the culture «, now thirty days old; the other from ^^-,, the fiftii renewal of a. Both rabbits died on the 7th and the 9th day, respectively. TIic lesions were itractically the same, with the addition of slight hemorrhagic lesions in the iu- testinal tract. The period of the disease was slightly prolonged. The result was not very satisfactory. If any attenuation was go- ing on, its, final attainment would demand too long a i)eriod of time. The experiment was therefore stopped and another undertaken. The temperature of the thermostat was raised to 45° C, to hasten the pro- cess of attenuation. ^pr. 23, agar culture. May 12, b. i. p. (b). May 22, rabbit inoculated. May 17, b. i. p. (b')- May 29, died. May 22, b. 1. p. (b'). It was found that cultures inoculated from b failed to develop at the assigned temperature, so that this exi)eriraent was not continue*! any farther. It deserves to be mentione (Culture dead. June 8, rabbit. June 15, dead. Juno 18, rabbit. Juno 24, dead. June 28, rabb:t. July 5, dead. Juno 4, 1). i. p. (a.) .June 8. 1). i. p. (fails to grow). June 13, b. i. p. (aj). June 18, b. i. p. (aj) Juno 23, b. i. p. (aj). (Supposed imiiurf, but found pure.) June 28, guinea pig. Juno 28, b. i. p. (34). July 10, dead. July 10, rabbit. -Inly 10, rabbit. (Remains alive.) (Uimains alive.) May IC, cigar culture. May 29, b. i. p. (b) (43io-4<° C.) July 14, placed at 3C°-3."o C. July 10, b. i.p. (as). (Culture dead.) July 25, rabbit. July 30, dead. August y, rabbit. (Reuiaina well.) August 4, b. i. p. (Sterile.) 171 The rabbits inoculated from the original culture after remaining at the temperature of 43.50-44° (J. for ten and twenty days died from the inoculation disease, but those inoculated from the same tube, after thirty and forty-three days, remained permanently well. This was not due to an attenuation of the culture, but to its death. Turning to the series of rabbits inoculated from the cultures renewed every tive or ten days, those receiving culture liquid ten, twenty, and thirty day« old died from the inoculation disease, while one inoculated after forty-three days remained alive, because the culture was dead, i. c, it failed to fertilize frrsh tubes after repeated inoculation. An adult guinea pig, inoculated from the same culture material, thirty days old, died in twelve days as a result of the injection. In this case only a few drops had been injected. This experiment demonstrates that in general the pathogenic i)ower of hog cholera bacilli is only destroyed by the death of the organisms themselves. This is a very important fac'. It will be remembered that in the attenuation of an- thrax bacilli their virulence was gradually diminished, and a time was reached when ihey failed to kill all but mice, while they still retained the power of multii)lying in nutritive liquids. In the above experi- ments even guinea-pigs, which are less suscei)tible to this disease than rabbits, died twelve days before the culture was found dead. The latter may have been dead some days before this, for no tests were made meanwhile. This fact has an important bearing upon the nature of the pathogenic activity of hog cholera bacilli. It shows that there are two elements involved, (1) the ptomaine action of the organisms; (2) their mechanical effect. That there is a ptomaine action of these bacilli has been con- clusively proved in the experiments of the Bureau made upon pigeons several years ago. But this ptomaine action is evidently secondary to the mechanical effect of the bacilli in forming plugs or thrombi in the blood vessels and thus causing destruction of tissue by impeding the circulation. This tendency to act mechanically is not lost as long as the bacilli are alive, as shown by their fatal effect on rabbits and guinea- pigs shortly before they themselves are destroyed. At the temperature employed (43.50-44o C), the original bouillon- peptone culture a died between the twentieth and the thirtieth day after the beginning of the exposure. The culture from this, renewed at the end of every lifth or tenth day, died between the thirtieth and forty-second day. Another culture b (see table), which had been re- moved from the thermostat after the forty-sixth day and kept at the temperature of the laboratory (about 300-33° C, during July) was still fatal to a rabbit on the lifty-seventh day. Another rabbit, inoculated ten days later, remained well, and a fresh culture made at the same time remained sterile, showing that theapparent immunity of the rabbit was due to the death of the bacilli injected. This experiment also shows pretty conclusively that the pathogenic power of these specific organisms expires oidy with their life, and not long before. 172 It is evident from our own experiments, and more recent ones made in France and Germany, conducted on the same lines, tliat the amount of immunity which we may expect to gain from preventive inocuhi- tion will depend on the quantity of ptomaines produced by the s])ecific microbes i. e., upon their poisonous nature. In other words, our suc- cess will depend upon the relation borne by the ptomaine to the disease process. If this factor is very great it is highly probable that prevent- ive inoculation either with ptomaines or with attenuated cultures will be successful. But if there is in addition a mechanical element, which may or may not overshadow in importance the ptomaine element, the problem is not only complicated, but may fail. There are two other points in connection with these experiments which demand attention. One is the variation in the length of life of the dif- ferent cultures exposed to the same conditions. This would be a seri- ous hindrance in obtaining vaccinal cultures of uniform strength, should this method ever ])rove successful. There was a noticeable change in the appearance of the serial cult- ures after a sojourn in the thermostat. There was a tendency to mul- tiply rather more abundantly, to grow in minute flakes and to rise to the surface to form a thin, unbroken membrane. The motility was somewhat impaired after a time. These changes gave rise to the sus- picion of impurities, but tests on gelatine plates showed that the sus- picion was unfounded. These experiments will be continued on pigs under similiar conditions to determine whether any immunity can be produced by this method. HOG CHOLERA, OR DISEASES CLOSELY ALLIED TO IT, IN OTHER COUiNTRIES. GREAT BRITAIN. This disease was first detected in 18G2, where it has been known under various names, the most common of which is swine fever. Owing to the fact that there are recognized at the present time three distinct in- fectious diseases of swine in different parts of Europe and America, it is impossible to state whether the disease known as swine fever in England represents two distinct maladies, hog cholera and swine plague, or hog cholera alone. This question can only be solved by a thorough bacteriological investigation, such as has not been made there in very recent years. There is enough evidence, however, to warrant the state- ment that hog cholera is prevalent in Great Britain. There is, on the other hand, no experimental basis for the statement that the other dis- ease, swine plague, also exists there. These two diseases produce le- sions of the large intestine, so easily confounded with each other, that great care must be taken in making a diagnosis. We must also con- sider that the three well marked swine diseases now known as hog cholera, swine plague and roitgct, were only a few years ago regarded as one disease designated by a great variety of names; that even to- day no clear idea exists among most pathologists as to what the precise differences between these diseases are. In a brief report on swine fever in Great Britain, by Professor Brown, of the Agricultural Department, in 1880, we do not notice that any doubt exists in his mind as to the oneness of the disease in Great Brit- ain and its identity with hog cholera. He even reproduces a plate from the report of the United States Department of Agriculture for 1885, in which the characteristic ulcers of hog cholera are shown as an illus- tration for his text. That there may be several diseases included under the term swine fever is evident from tiie statements made in this report concerning the annual importations of diseased swine from other countries. Swine fever is said to have affected animals imported from Holland, Denmark, Sweden, Norway, and the United States. Now, hog cholera appeared in the North European countries for the first time in 1887. The swine marked diseased may have been affected either with swine plague, which exists on the Continent, or with lighter non-infectious forms of lung disease not uncommon in pigs at any time in the year. 173 174 We quote, from Professor Brown's report tbose parts wliicb may prove iuterestiug- to American readers, using- the languageof the report itself whenever possible: ISymptoms of su'ine fever. — It is most important that the farmer should be acquainted with the signs which indicate the existence of swine lever at tlie earliest period of its development ; bnt unfortunately the disease is very difficult of detection in the early stage in the greater number of cases, and the symptoms which are generally believed to be specially indicative of the affection, viz., redness of the skin on certain ])ortions of the body, and diarrhea of a i)eculiar kind, do not appear until the disease is fully developed, and in nnmerous instances are not ob- served at all. The animals W^ed fairly well, show no rise of temperature ; they are vigorous, and for several days, and even for several weeks, be- tray in no way the disease. It requires very careful and prolonged ob- servation to notice that at one time or another — at any rate at rare in- tervals — the swine have a short cough, not an important departure from the healthy state. Very few experts, to say nothing of the owner of the pigs, would suspect swine fever because he happened to hear the ani- n)als cough at rare intervals; and there is in these mild cases, which Dr. Klein considers constitute the majority, absolutely nothing else which would be noticed; the ski-n remains quite free from any appear- ance of disease. It is true that the inguinal glands are distinctly en- larged, but nidess the owner thinks of inspecting these small lymphatic glands (kernels) under the skin of the pig's groin, and knows what their proper size is in health, he has no chance of recognizing the dise.ise in this obscure form. In the organs of these ai)parently healthy pigs there are found on dissection very pronounced symptoms of disease, so pronounced in fact, that it seems astonishing that during life the ani- mals presented such slight signs of it. And these very slight signs, it may be remarked, were only noted by the observer in the cases of pigs which were under constant observation after they had puri)osely been infected with the disease. Swine which are affected with swine fever in the occult form may be moved about freely, sent to market, bought and sold over and over again, distributing the infection wherever they go, without exciting the least suspicion in the minds of those who buy or sell or keep them that they are infected with a deadly and highly contagious disease, and in this way many outbreaks may occur without the origin of the infection being discovered. In the more pronounced forms of swine fever the symptoms which are shown by the sick animal will uot be very definite until the affection is fairly advanced. Dullness and diminished appetite, with hot skin and occasional shivering tits, with rise of internal temperature from the normal 103° to 105° or 100° F., are among the first signs of infection, and should always be taken as justifying a strong suspicion of the ex- istence of swine fever, espedialiy if the disease is known to be in the locality. It has been remaiked that pigs when suffering from swine fever in the early stage often seek to hide themselves beneath the litter on the floor of the stj* ; but this action is so common among swine that it would hardly be likely to attract any attention, and even when noticed it would not be looked upon as a symptom of any disease. There is, however, to the practiced eye a great difference between a healthy pig, which, in its desire for warmth, or quiet, or for some other reason, buries itself under a lot of litter, and one which performs the same act inobe- 175 dieuce to the instiuctivc oftoit of a sick aiiiinal to jrct out of the way of the light aucl its coiiipauioiis, and everything nuder the sun, and suffer in seclusion. Tlie liealthy pig when disturbed emerges from its rt'treat al( rt and ready for action. The sick one objects to move, and if compelled, crawls tVoni his lair, trembling and discontented. Sometimes tliere ai() signs of partial paralysis, and the pig moves in an unsteady manner trom side to side, Irequently losing the use of one or buth hind quarters, aiul dropi)ing to one side, or dragging both hind legs as it attempts to move forward. There is no loss of sensibility wilh the defective motion, as the animal if touched will indicate pain by a sharp cry. Diarrhea may occur early in the disease, after a short period of con- stipation ; and the evacuations are generally light in color at first, be- coming darker by and by, often from the mixture of effused blood. In severe cases the intestinal discharge consists almost entirely of blood, with masses of clot and loosened |)ieces of exuded lymph from the in- flamed and ulcerated mucous membrane of the digestive canal. A symptom which is considered to be characteristic of swine fever may sometimes be detected early in the disease. Eed patches or blotches a]ipear behind the ears, inside the arms, and under the bell^'. Professor Axe describes a distinct eru])tion in the form of red spots, from one to three lines in diameter, slightly raised above the surface, so that they may be felt by drawing the finger over the skin. The erup- tion is not always present, and often there are not more than half a dozen spots extending over a large surface; but in other cases they are very numerous. After two or tlirce days the spots subside, and are followed by a second, third, or even a fourth crop, and after their final disap- pearance the cuticle becomes ragged and scales off. Small water bladders (vesicles) appear on the surface of the red spots when the fever remains very high, and the tluid contained in them either escapes or becomes dried up, forming a gray crust on the surface. Discharges of thin fluid from the eyes and nose commonly takes place early in the course of the disease, and, as it advances, the discharge becomes thick and purulent, sticking about the eyelids and openings of the nostrils. Diarrhea is more constant as the disease goes on. The voided matter is offensive and often streaked with blood; prostration occurs and is soon followed by complete collapse, and the animal dies in a state of unconsciousness or in violent convulsions. Death may take jdace at various periods from the commencement of the affection, some- times after a few days' illness, while in other cases tie animal may linger for two or three weeks. In reference to the change of the color of the skin in marked cases of swine fever, it may be observed that there ma^^ be, independently of the raised spots which Professor Axe describes, a diffused redness, or regular i^atches of redness, or a purple tinge in different parts of the surface; but these signs are not to be expected in all or even in the majority of cases of the disease; and it is well known that redness of the skin is a symptom of some common diseases of swine. It arises, for example, from exposure to wet and cold ; contact with sea- water, or spray during a voyage, will also produce it; a journey in a railway truck which has been lime washed is another cause; consumption of wash with which salt liquor has been mixed is followed by severe, often fatal, inflanmiation of the mucous membrane of the digestive canal and sympathetic irritation of the skin; and the symptom has also been noticed in acute indigestion which has resulted from eating freely of mangolds. Redness of the skin, therefore, either in patches or gener- 17G ally, cau not be acce[)ted as snfficieiit ovideuce of the existeuce of the swine fever. In certain instances tlie symptoms of swine fever may be so well de- fined during life that an opinion may be given promptly and withont much risk of error, but ni^^ler ordinary conditions the conclusion must be the result of the careful consideration of the history of the outbreak, or of the evidence which can be obtained by dissection of the organs of a diseased animal; and for this purpose it is better to kill a suspected pig than to take the carcass of one which has died some time before the commencement of the inquiry, and has probably undergone post-mortem changes which will render obscure the true morbid appearances. Experience has placed beyond all doubt the fact that swine fever when it once obtains a hold on a herd of swine does not spare them. It is true that a proportion, and it may be a considerable one, of the older animals particularly, will escape with a mild attack, and in some of these mild cases there will be no characteristic symptoms to attract attention. In fact, it will appear that animals have escaped the dis- ease ; but the critical observer will find some signs of the disease in the majority of the swine which have been exposed to infection. Cases which arc often reported of swine fever attacking two or three swine of a large herd and sparing the rest may safely be put down to the credit of any disease but swine fever. And the same thing may be said of those cases which are traced to the consumption of indigestible food, or the exposure of the animal to hardship or unsanitary conditions of exist- ence. Fostmortcm appearances in sicine fever. — Some of the changes which are affected in the organs of the body by the ravages of swine fever can only be appreciated by the pathologist ; others, and those most distinctive perhaps,, are patent to the ordinary observer; and on this point it is worth while to note the description which was given before the members of the Eoyal Agricultural Society in 18G5 by Dr. William Budd, of Clifton, who was the first scientist in this country to investi- gate the disease, which was at that time looked upon as a new one. Dr. Budd's attention was particularly attracted to the changes which Lad occurred in the digestive organs, which he called a series of ulcer- ations of peculiar character, variously distributed over the intestinal tract, from the stomach to the rectum inclusive. The first stage of the local affection appears to be the development (amid all the phenomena of acute inflammatory disturbance) in the sub- stance of the mucous membrauce and in the submucous tissue of an adventitious deposit (or cell growth) resembling in manj^ of its charac- teristics the well-known yellow matter of human typhoid. When Dr. Budd gave this description, the outgrowth from or deposits on the mu- cous membrane of the stomach and intestines were seen more frequently than they have been of late years; in fiict, in all well marked cases they were the prominent objects in the post mortem appearances — soft, spongy masses, sometimes in very severe cases stained a dark red by the blood, which was extravasated into the intestines, varying in size from that of a large pea to a walnut, circular or oval in shape; some- times several masses were joined together; but whether large or small, separate or confluent, the deposits, from their color in contrast with the membrane on which they were placed, were very striking objects. A very curious appearance was sometimes seen in the intestines of swine which had partially recovered from the fever and afterwards died from exhaustion, or were killed for the purpose of examination. The mucous membrane in these cases was spotted with the small masses of 177 deposit wliicli had lost the soft, spongy or fungoid character, and be- come dense and, so to speak, leathery looking, not unlike yellow leather buttons, marked with concentric rings, or, as Dr. Budd remarks, like slices of columba root.* The first simile will i)erhaps be more suggestive to the farmer than the latter, as slices of columba root are not familiar objects. The mu- cous membrane of the intestines, especially the large intestines, was often covered with ulcers, and the masses of deposit which have been referred to were generally found to be in connection with deep excava- tions, the result of the ulcerative process ; but in all cases the edges of the ulcers were elevated above the surface of the mucous membrane, and presented a soft fungoid character. In some cases the whole of the mucous membrane of the intestine was covered with a croupous or diphtheritic deposit of a dirty white color; and it was only after the deposit had been cleared away that patches of inflamed, and perhaps ulcerated, structure could be seen. In some instances tlie dipliiheritic deposit was so abundant as to fill the intestinal tube, and leave no canal for the passage of the feculent matter, and rupture of some part of the intestine was the natural re- sult of this blocking up of the passage. The next illustration is copied from a report on swine plague in the Keport of the Bureau of Animal Industry, Washington, United States (for 1885), and it may serve to indicate at the same time the character- istic appearances of the disease and the identity of the swine plague (hog (;holera) in the United States of America and the swine fever of this country. Besides the appearances which have been described as occurring in the stomach and intestines, especially in the large intesrine, there are nearly always observed patches of congestion in the lungs, with here and there condensation of the lung structure, which ])resent a ilesby character quite distinct from the healthy state. There are also changes, easily distinguished by the pathologist, in the liver, kidneys, spleen, lymphatic glands, and also in the cr^vities of the heart. In short, it may be aflirmed that the moibid changes in swine fever are so ])er- fectly well detined that no error in opinion can occui when all the evi- dence which a post mortem inspection aftbrds is in possession of the inquirer. In this description we are led to infer that the writer has before him genuine hog cholera. At the same time some of the features dwelt upon, such as the croupous and diphtheritic deposits or exudates in the large intestines, are more like those found in severe epizootics of swine plague. t There is another fact which proves that at least part of the swine fe\ er of England is the hog cholera of the American continent. This is presented by the investigations of E. Klein. In his report upon swine * These neoplasms wo have also encouutereil chiefly in adults. They mnsb be looked upou as results of a greater resistance on the partof tlie mucous membrane, such as we may expect in old animals. t A phigiie like hog cholera may ]ierhaps change its character under influences such as climate and locality, or under influences found in race, breed, etc., of animals. This may frequeutlj' account for modifications of diseases causfd by the same micro- organism. 15612 H c 12 178 fever in the supplement to the Seventh Auimal -Eeport of the Local Gov- eniiueut Boanl for 1877 Dr. Kleiu gives a very good account of the pathological anatomy of this disease, together with some researches on The nature of the cause and the mode of infection. Though calling the disease pneumo-enteritis, his text, as well as the statements of Professor Brown, quoted above, show that the accompanying lung disease is no more severe than in hog cholera. The microbe which he described in this re[)ort is a large spore-bearing bacillus. The methods which he emi)loyed in his bacteriological work were those of the times, not con- sidered now as capable of giving any trustworthy information. Conse- quently, at a later date he regarded it as necessary to again go over the ground, and published his results in Yirchow's Archiv, XCV, 4C8, in IbStt. In this monograph he describes the inoculation disease in mice and rabbits very much as we have found it, laying particular emphasis u[)o;i the coagulation necrosis found in the liver. His cultures con- tained a motile bacillus from .002 to .003 millimeter in length. We may therefore conclude that a germ closely resembling or identical with the hog cholera bacillus is found in cases of swine fever, and that hog cholera actually exists in England. The history of the struggle with swine lever in Great Britain since 1878 shows that it has been very severe. iSTumcrous orders have been issued, beginning with the contagious diseases aet in 1878, to restrict the extension of the disease, but all appear to have been without avail, since the malady was as widespread and as virulent in 1885 as ever before. This was without doubt due to the inefiicient and incomplete execution of the orders. By the order of December 17, 1878, the slaughter of swine affected with the disease was made compulsory, and compensa- tion was to be paid out of the local rates for all swine slaughtered by order of the local authorities. The order also provided that no swine should be moved out of a pig-sty or other jdace without a license, and then only for slaughter. After this order had gone into effect weekly returns were received from the inspectors of local authorities, which showed that in 1870 the disease had prevailed, at some time during the year, in forty-four counties in England, six in Wales, and three in Scot- laud. The continued spreading of the disease gave rise to the swine fever order of 1879. This contained provisions for the declaration of infected places and for the slaughter of healthy swine which had been herded with diseased ones, and also for regulating the exposure for sale of swine in fairs and markets. This order was only partly carried out, for out of 17,074 swine attacked 3,410 were allowed to die and 124 recovered. In 1882 the disease was more prevalent than in 1870. Slaughter of diseased and exposed animals was continued as before. Tlius of 14,703 swine attacked 11,903 were slaughtered, 2,799 died and 18 recovereer a country: "The disease did not, as was supposed, appear in Marseilles toward the end of June, but in the month of April, and I have been able to locate three entirely distinct centers of the outbreak due to tlie same cause — the introduction of African swine. These three centers are : The village of Caillols, midway between Aubagne and Marseilles ; the village of St. Marthe, G'^'". northeast of Marseilles, and the herds of the Mediter- ranean distilleries. (I) From the 10th to the 15th of April, a breeder of Caillols received a drove of black swine from the province of Oran (Algiers). From the lirst week some cases of paeumonia| showed themselves among the last animals; the disease gained rajiidly, causing many deaths. The surviv- ors v/ere sold on the 1th of May following. On the 8th of June the same piggeries were restocked, partly with African and partly with Russian swine. Towards the end of the month there were cases of pneumonia. The Russian swine resisted less than the others. August IG the piggery was again emptied. Finally during September the third attempt was made, exclusively with African swine. This also i)roveda failure. The survivors were sold in October. During this time the disease reached the neighboring piggeries stocked with a mixed Marseilles breed. The breeders of Caillols, alarmed by the ravages of an ei)izootic the nature and cause of which they dul not know, decided to sell out at any price. The neighboring localities, St. Marcel, St. Loup, San Joan dii Desert, etc., were successively infected. Infection v\'as spread by the sales and exchanges of sick and suspected animals, by means of trans])ortation (carts often used in common by sev- eral establishments soiled by the dejections of the sick and afterwards used to transport healthy animals and their feed), and also by the lat- eral canal of Hu^■eaune, which receives at certain points running water coming from the grounds on which the piggeries are located. At the beginning of September all the valley of Huveanne, from Au- bagne as far as Marseilles, was infected. Diseased ])igs from this re- gion we meet again in the market of Aubagne, at the fair of September 21, and which became later one of the most active agents in spreading the disease in the departments. (L*) Toward flic middle of the month of August the disease appeared in a piggery in St. Marthe, stocked exclusively wMth African swine. These animals came directly from Oran without coming in contact with any other of their species. Several days later one of the largest breeU- ers in that vicinity, who for three months had not brought a single pig to his establishment, and whose piggery was at least GOO feet away from the preceding one, sustained a considerable loss, especially among the pigs of 130 to 175 pounds. * lu a locont review of tlie ie}inrts of the Burean of Animiil Iiulnstry by Dnclanx (AiDinh'S dc V fnstitiit Pasieur, July, 1888), the reviewer regards this disease as iden- tical with hog cholera, and states that Coriiil and Chanteniessc had at first overlooked the molilitii of the r/enn thev were stndviug. 1 1 c. p. G7U. t The writer calls the disease infections pneumonia for want of a l)etter term, although Rietsch distinctly states the intestinal nature of the malady. Fouquc was no doubt led astray hy the early, misleading notices of Cornil and Chantemesse. 189 (3) Filially, on the 2oth of June, sick pi.i>s came from Oran to the pig- geries of the Mediterranean distilleries. There were very soon a num- ber of victims of [)neumonia, not only in the distilleries but also in the neighborhood, where there ^Yere from 4,000 to 5,001) in a comparatively small territory. A great many of the sick died ; the others were quickly sent to ditiereut cities to be delivered to the butchers. I have traced the history of six sows which were sold from the midst of infection to Estaque; thence they passed through the commune Rove and arrived in August at Gignac, where they introduced the disease. By an odd coincidence some sick pigs from the same locality were taken to the fair at Aubagne and bought by a breeder of Gignac. The fair at Aubagne, on September 21, marked the most important phase in the progress of contagious pneumonia. During the first fort- night in October there was a veritable ex[)losion of the disease, which, up to this time, had been scarcely known. The importation of the disease by aniuials bought at the fair of Au- bagne can be traced with the great st precision in the suburbs south and north of Marseilles, also as far as Gardanne, in the communes of Septemes, Vitrolles, Pennes, etc., to Gignac, as mentioned above, even into the neighboring dci)artments, which continued with the others to receive consignments of Marseilles swine. It is also necessary to men tion Puget, Ville et Grasse, among the localities infected. In the beginning of December 153 swine were shipped from Mar- seilles to Nice; nearly all died in a few days. From that time cases ai)peared among the native pigs. Un December 22 another lot of 133 pigs were shipped; 33 were des- tined for Nice and 100 for Italy. These last were sold on the 24th, in the market of Vintimille; nearly all died very soon. For several years Marseilles annually exported to Spain, and es])e cially to Barcelona, a great number of pigs. Contagious jjuenmonia had been causing losses there for several months, even, it is said, at Majorka, in the Balearic Island^-. The Spanish breeders, believing the outbreak of the disease with them was attributable to the importation of French ]:>ork, obtained from the authorities the permission to imi^oso a quarantine of six days, at Port Bouc, on swine from Marseilles, to be- gin on the 1st of the following February. This measure has not been enforced up to the present day. From what has preceded I believe 1 can conclude that the epizootic of contagious pneumonia which has raged during the year 1887 in the interior of France, and which at this time continues its ravages there, is of African origin. It has been introduced by Algerian swine which came from the province of Oran. This disease has made 20,000 victims in several mouths in the province of Bouchesdu Phone. Pigs, and especially those from three to nine months old, areoftcnest attacked; larger pigs appear less susceptible. The Marseilles breed, the English (Yorkshire and Berksliire), and the Kussian swine are more susceptible than the African swine. T\A o months ago about 50 pigs two to three months old, coming from Cazeres and Le Fousseret, in the arrondissementof Muret, were used to stock a farm in Gignac. These pigs, placed in the pens which had con tained sick ones, and which had only been very imperfectly disinfected, remained in good health, while more than a hundred cases of conta- gions [)neumouia appeared around them in the same piggery. After- wards more than 2,000 Gascon swine were imported by the single com- mune of Gignac. Up to the present time the disease has not re-a])peared. Are we here confronted bj a new example of natural immunity com- 190 panible to that noticed long ago by Cbauveau in Algerian sheep in regard to anthrax ! " Taking into consideration what we know now of these epizootics and enzootics of swine diseases in foreign conn tries, we are forced to the conclnsion that the disease in Sweden, Denmark, and France is closely related to if not identical with hog cholera as it is found in our own country, while the minor differences in the disease as manifested in these epizootics, and in the germs producing it, can be explained on the principle of the variability of disease germs, a principle in favor of which much evidence has already been obtained in recent bacteriologi- cal researches. DESCRIPTION OF PLATES. Plate I : Casciiiii of a pig aftecte.ci with bog cholera laid open to sliow the ulcers of tho laucous luombrano. Th(5 ileo-ciccal valve is Dear the center of the page, and the small intestine, with tho cut end tied, is above. The smallest ulcers have slonghsofa uniformly yellowish color; the larger ones have zones of differ- ent color, while the largest are brown or blackish. It will be seen from the plate that the slongh or new growth in most ulcers projects slightly like a small flat button. Plate II; Caicum of a i)ig fed with viscera from a case of hog cholera, slit open to show the mucous membrane thickened and quite uniformly necrosed, with isolated deeper ulcerations. The ileo-crecal valve is very much thickened, its mucous membrane ccchymosed and ulcerated. The lymphatic glands of the meso- colon and those in tho angle formed by the entrance of the ileum into the csecum are purplish, with cortex engorged with extravasated blood. They illustrate tho condition of the lymphatics of both thorax and abdomen in the acute hemorrhagic form of the disease. Plate III: Caecum of a pig inoculated with blood from a case of hog cholera. The entire mucous membrane is necrosed. In the upper portion of tho figure about the valve there are groups of minute pigment spots. The valve is open to show tho intact mucosa of the ileum. This figure also serves to illustrate the con- dition of the mucous membrane of ctecum and colon in ]>ig8 fed with cultures of hog cholera l)acilli. Plate IV: CcBcum of a pig, showing round and elongated ( avities on and around the ileo- cEecal valve. These are ulcers from which the slough dropped away during removal. The base of the ulcers is formed by the muscular tissue of the in- testinal wall. Tbe ulcers appear as if the mucosa had been punched out with a sharp instrument. The edge of tho ulcers in the u[)per portion of the colon with the slough still adherent. The lungs in this animal were normal, if we except a few collapsed areas from one-half to tbreo-fourths inch across. Plate V: Ulcers in the lower portion of the small intestine (ileum); not very frequent. Note the large, deep ones with puckered, ragged border, and the very small ones with a thin superficial slough, stained with bile. Plate VI: Kidney from pig No. 7 (see p. 41), showing tho hemorrhiigic coiulition of cortex and engorged glomeruli. In this animal the disease was marked by the hemorrhagic condition of other organs. 191 192 Plate VII: Right lung from a caso of hog cholera. The luDg tissue is nowhere iufiltrated or hepatized, hut studded with hemorrhagic sx^ots which are found iu the parenchyma as well as under the pleura. This animal, placed in an infected pen, died on the twenty-second day of exposure. There were hemorrhages iu the subcutaneous connective tissue ; lymphatics in general hemorrhagic. Petechia) iu stomach and large intestine. In the crecum and on the valve a few ulcers with hemorrhagic base. Plate VIII: Heart with subepicardial hemorrhages especially numerous on left auricle. Plate IX: Fig. 1. Collapse of various groups of lobules in the pr-ucipal lobe of a pig's lung. Frequently found in young pigs which have died of hog cholera, in those af- fected with lung worms, and in a small percentage of those slaughtered dur- ing health. Fig. 2. Broncho-pneumonia aifecting animals under various conditions and not infrequently fouud iu animals which have succumbed to hog cholera. (See j). 54). The air cells and smallest air tubes arc shown distended with a yellow- ish material which is of a dry, caseous consistency, and may be teased out in the form of minute branching cylinders. Plate X: Fig. 1. From a cover-glass preparation of the spleen of a pig which died of hog cholera. Stained in an aqueous solution of methyl violet and mounted iu balsam. Outlined with a camera lucida, using a -j^ homog. immersion (Zeiss), ocular 2 (x 800) : a, distorted red blood corpuscle ; h, bacilli iu pairs. Fig. 2. Section from the enlarged and cougested spleeu of pig No. 94 (see Secoud Annual Report Bureau of Animal Industry, p. 193), which died very suddenly with extensive hemorrhagic lesions of A^arious organs. Spleeu hardened iu alcohol two hours after death ; stained iu aniline water methyl violet and decolorized in 1 per cent, acetic acid ; mouuted in xylol balsam ; outlined as in Fig. 1. Note the large group of bacilU occupying the capillary meshes of the siileen pulp, all extra-cellular. Plate XI : Illustrative of the growth of hog-cholera bacilli on gelatine. Fig. 1. Various colonies from gelatine plates : a, embedded in the gelatine layer (deep colony), usually spherical or egg-shaped; ?>, flattened colony growing on the surface of the gelatine layer; c, c', c", growing betweeu the layer of gelatine and the glass plate as very thin films; the knobs on c', c" repre- sent the part of the growth in the gelatine layer. Fig. 2 represents both deep {a) and surface colonics (h) growing iu a gelatine layer coating the inner surface of a test tube. A tube of gelatine was inocu- lated by stirring up in it, while liquid, a minute fragment of spleeu tissue from a case of hog cholera (No. 464, p. 51), transferriug a drop from this to a second tube, and then rolling out the latter in ice water. Culture seven days old. The zones on the surface colonies are very liiiely due to changes of tem- perature in the laboratory, alternately retarding and augmenting the growth. This mode of growth is by no means common. Figs. 3, 4, .'> represent the growth of hog cholera bacilli iu tubes of nutrient gela- tine, showiug the isolated colonies iu the depth of the gelatiue and the con- fluent growth on the surface. Fig. 3 represents a culture three days old (epizootic near Washington City, 18S5), inoculated from the spleeu of a pig. -Fig 4, fourteen days old, inoculated from a culture which was prepared di- rectly from the spleen of a pig iu Illinois, 1886. Fig. 5, inoculated from the blood of a rabbit which died from inoculation with bacilli from Illinois cult- ure ; ten days old. The difference in growth observed may be due to a greater or less alkalinity of the culture medium or to a slight physiological difference in the bacilli themselves. 193 Plate XII : Fig. 1. Jgar agar culture of hog cholera bacilli in thermostat, four days old. Fig. 2. Potato culture under a bell glass, twelve days old. Fig. 3. Potato culture in a test tube containing an abundance of moisture. The plug was made impervious with sterile paraffine. The growth is whitish, very glistening. The difference in color between Fig. 2 and Fig. 3 is caused by the different conditions of moisture. Plate XIII: Fig. 1. Coagulation necrosis in the liver of arabbit which died six days after in- oculation. The small, yellowish spots are groups of acini completely ne- crosed. The larger patch to the left shows the necrosis in the form of a net- work. Fig. 2. Liver of a rabbit inoculated with one thirty-second cubic ceutimeter (by dilution) of a beef infusion peptone culture one day old. Dead on the seventh day. The coagulation necrosis on the left is more ditfuse. On the right are cysts of coccidium oviforme. Fig. 3. Enlarged spleen from the same rabbit (natural size). Weight of rabbit, 1| pounds. The spleen of this rabbit was but moderately enlarged as com- pared with the spleens of most rabbits which succumb to hog cholera. Fig. 4. Spleen from a healthy rabbit weighing 2| pounds (t. e., one and a half times the weight of the diseased rabbit. Plates XIV, XV, XVI : Photomicrographs of hog cholera bacilli which developed in different media. All were made at a uniform magnification of 1000 diameters, with the Zeiss apo- chromatic objective of 3™™ and 1.30 numerical aperature, using projection ocular No. 4 and Abbe condenser with largest diaphragm. Orthochromatic plates and picric acid screen. Plate XIV : Fig. 1. Coverglass preparation from spleen of rabbit inoculated with hog cholera bacilli. Stainec>two to three minutes in aqueous solution of fuchsin. Mounted in xylol balsam. X 1000. Fig. 2. Coverglass preparation from bouillon-peptone culture five days old. Stained in aniline-water- fuchsin for five minutes, and decolorized in one per cent, acetic acid for a few seconds. Mounted in xylol balsam. X 1000. Plate XV: Fig. 1. Coverglass preparation from bouillon-peptone culture one day old. Stained same as Fig. 1 of Plate XIV. Mounted in xylol balsam. X 1000. Fig. 2. Coverglass preparation from gelatine culture two days old. Stained same as Fig. 2, Plate XIV. X 1000. Plate XVI : Fig. 1. Coverglass preparation from colony of hog cholera bacilli taken from an Esmarch tube, made directly from spleen of pig, fifteen days old. Stained same as Fig. 1, Plate XV. X 1000. Fig. 2. Coverglass preparation of hog cholera bacilli from agar culture fifteen days old. Stained same as Fig. 1, Plate XIV. X 1000. 16612 H C 13 Plate I. Plate n. Plate IK. U L C E U AT K D CAK( I U M A.f^QeniC. Ll:n.ca:,-.;i,: 3alti Plate "R'. I u ; r e \ . / f Plate YT. ULCERS IN ILEUM. A.Koen* Co. lirhiicduitic. Baltic Plate YR. ■^4i^* Plate ^mi. \^^ -. N ^ V \:V HE MORRHA( VIC HEART Plate f Q.Marx fecit HieniCQ.lirhoMOitic, COLLAPSE AND BRONCHO -PNEUMONL'l. Plate X. Fio.l. 'A n 3 v-^^ Fig. 2. (*> -*>• *^ »^> 0^ a e.AIarx fecit. HOG rHOLP:F^A BACILLI Plate XJ. c^ Fio.l Fig. 4. Fro. 5. Fjg.2. Fic3 G.Marx fecit. CULTIVATION OF HOG CHOLEHA HACILIJ. Plate XII CT.Marx- fecit A.HaeniCo.liThocdus:!:. Saltitr CULTIVATION OF HOCi CHOLEKA BACILLI, Plate inr. DIAGNOSIS OF HOG CHOLERA BACILLI- ( RABBIT plate xiv Photomicrographs of Hog Cholera Bacillus. ^-; ^ *#> '^ / I' v% COVERGLASS PREPARATION FROM SPLEEN OF INOCULATED RABBIT. •T* • • \ / * . . • . . • \ « ■^ ^ ' I . \ • \» I % / Fig. 2. X 1000. COVERGLASS PREPARATION FROM LIQUID CULTURE FIVE DAYS OLD. PHCrO- CHAVURE CO. NY. I PLATE XV Photomicrographs of Hog Cholera Bacillus. b « •v.* Fig. 1. X 1000. COVERGLASS PREPARATION FROM LIQUID CULTURE ONE DAY OLD. i -.i' •' - #^' ♦ *': % Fig. 2. X 1000. i- COVERGLASS PREPARATION FROM GELATINE CULTURE TWO DAYS OLD. 'HOTO ORAVURF i; O. N. PLATE XV Photomicrographs of Hog Cholera Bacillus. \ } Fig. 1. X 1000. COVERGLASS PREPARATION FROM ROLL CULTURE (eSMARCH TUBe) FIFTEEN DAYS OLD. ■j • K> ( Fig. 2. x 1000. COVERGLASS PREPARATION FROM AGAR CULTURE FIFTEEN DAYS OLD. PHOrO-GRAVURE CO. H INDEX. Page. Agar-agar cultures 08 Attenuation of hog cholera virus by heat 107 Bacillus of hog cholera, description of G3 Bacteriological observations 38, 58 Biology of hog cholera bacilli GG Brine, vitality of virus in 88 Burial of carcasses 126 Butyric bacilli in hog cholera cases 58 Buzzards as carriers of disease 01 Calomel, effect on swine 136 Carbolic acid as a disinfectant 88 crude, as a disinfectant Dl Cathartics, effect on swine 135 Causation of hog cholera 03 Chloride of zinc as a disinfectau#. 90 Complications in hog cholera 54 Contact with the sick producing hog cholera 51 Corrosive sublimate {see Mercuric chloride) 88 Cultivation of hog cholera bacilli GG Cupric sulphate as a disinfectant 90 Denmark, swine disease in 181, 183 Detmers, Dr. H. J., investigation of hog cholera 28 Diagnosis of hog cholera bacilli 06,09 Digestive tract as a channel of infection 105 Diseased viscera, feeding to swine. {See Feeding.) Disinfectants, effect on hog cholera virus 8" use of 131 Distribution of hog cholera bacilli iu the body 05 Drying, effect on hog cholera bacilli 78 Dysentery, relation to hog cholera 122 Etiology of hog cholera. {See Causation.) Feeding hog cholera bacilli to swine 107 viscera to produce the disease 50, 105 Food as a means of infection 105 Fowls, effect of inoculation on 73 France, swine disease in 18G Freezing, effect on hog cholera virus 7G Gelatine cultures of hog cholera bacilli 07 Great Britain, swine fever in 173 Guinea-pigs, inoculation disease in 73 Heat, effect on hog cholera virus 75 Hemorrhagic lesions 34, 52 History of hog cholera in the United States 9 investigations l"! 195 196 Page. Hog cholera, bacillus of .".' 63,(36,75,78,80,87 causation of «)5 history of investigations concerning 14 introduction and spread in the United States [) or allied diseases in France ISO Great Britain 173 Sweden and Denmark 181 prevention of 26 produced by feeding 50, 105, 107 inoculating pure cultures of hog cholera bacilli.. . 55 treatment of 25, 135 Hydrochloric acid as a disinfectant 91 Illinois, investigations iu 110 Infection of swine, modes of 105 Inoculation experiments. (See Preventive inoculation.) of small animals with hog cholera bacilli 60 Iodine as a disinfectant ' 89 Isolation iu hog cholera 123 Klein, E., investigations in swine diseases 177 Law, L>r. J., investigations iu swine diseases 19 Laws with reference to hog cholera 127 Lime as a disinfectant 03 Lundgren, Dr. J., investigatious of 185 lAiugs, infection by way of 112 Lung lesions in hog cholera ? 54 Marseilles, spread of swine diseases from 188 Maryland, hog cholera in ^ 50 Nebraska, investigatious in 116 Pathological action of hog cholera bacilli 113 Pens, vitality of virus irx- — -- 86 Permanganate of potash as a disinfectant 89 Pigeons, iuoculatiou of 73 vaccination of, with sterilized cultures 155 Plates, description of 191 Fost-mortem appearances iu hog cholera 34, 39, 59, 106, 107 Potato cultures 68 Prevention of hog cholera 26, 123, 170 Preventive iuoculatiou of swiue by feeding 151 with small doses of strong virus 139 with sterilized cultures 150 Prevention of swiue fever ^ 170 Public health, relation of hog cholera to 120 Rabbit, disease produced by feeding 72 Rabbit, inoculation-disease in 70 Snow, Dr, E. M., investigations of 17 Soil, disinfection of, with lime -^^ vitality of hog cholera bacilli in 80,86 Spores, do hog cholera bacilli produce 101 Staining of hog cholera bacilli 65 Streams distributing virus 126 Subcutaneous iuoculatiou of swiue 109 Sulphate of copper. {See Cupric sulphate.) Sulphuric acid as a disinfectant 30 Sutton, Dr. G., investigations of swine diseases 12, 14 197 Page. Swedeu, swiue diseases in 181 Swedish and Aiuericau liog cholera, comparison of 185 Swiue fever, jiost-moriem lesious in 176 symptoms of 174 Symptoms aud post-mortem appearance in hog cholera 33 Table of hog cholera epizootics in the United States 11 Tables showing vitality of hog cholera bacilli in the soil 81,83,84,85 Treatment of hog cholera 25, i:i5 Typhoid fever, relation to hog cholera 121 Ulcerative lesions 35,53 Vacno cultures 69 Veins of swiue, inoculation into .•. Ill Vitality of hog cholera bacilli in the soil 75,80,86 Virus, attenuation of, by heat 167 Water, life of hag cholera bacilli in 76 o ^ ^