Special report on the cause and prevention of swine plague

Table Of Contents

Page.

Letter of transmittal 7

Investigations concerning the nature and etiology of swine plague 9

I

During the summer of 188G the writer made a number of post-mortem examinations of diseased pigs in Illinois,! for the purpose of identifying, if possible, the swine diseases existing in the Western States with the disease of hog cholera (or swine plague as it was then denominated), under observation since November, 1885, on the Experiment Station near Washington. It will be remembered that the hog-cholera bacillus was discovered in November of 1885, and carefully studied as to its morphological and pathogenic characters.

The post-mortem examinations were made in the field, the spleen removed, placed in a sterilized bottle, and the cultures made either immediately or several hours later, indoors. During the first visit to Illinois in July, 1886, pigs were examined in Marion, Champaign, and Henry Counties. In some cases the lungs were diseased. In most cases the intestines were more or less ecchymosed, while ulcers or indurations of the mucous membrane were rare. What was most surprising, however, was the absence of any bacteria in the spleen of seven out of eight animals examined. In the eighth case there was considerable pneumonia associated with pigmentation of the mucosa in the large intestines. The culture from the spleen contained two species of bacteria, the bacillus coli communis, a common inhabitant of the digestive tract of the pig and other domesticated animals, and a small, non-motile bacterium which possessed pathogenic properties as the inoculations made at that time distinctly demonstrated. These bacteria were isolated by inoculating a rabbit subcutaneously with a bouillon culture containing both kinds of bacteria. The rabbit died in 7 days with extensive inflammation of the subcutaneous tissue starting from the point of inoculation. Cultures from the spleen, liver, and blood contained onl^^ one form, the oval non-motile bacterium. A second rabbit, which received one-sixth cubic centimetre of a pure bouillon culture of these bacteria under the skin, died in 3 days with beginning peritonitis. Two mice, inoculated in the same manner, died respectively 1 and 2 days after inoculation.

'Already published in detail in various reports of the DeiJartmcnt of Agriculture. tSee Rei)ort of the Bureau of Animal Industry for 1886, p. 76.

Much time was spent in studying tlie motile bacillus, owing to its superficial resemblance to hog-cholera bacilli. Any one familiar with intestinal bacteria will, I think, at once concede, after reading the description on page 78 of the report referred to, that this was the bacillus coli. The peculiar expanding and rapid groM th on gelatine, the coagulation of milk, the offensive, putrescent odor of the cultures, are properties which do not belong to hog cholera bacilli. ' Moreover there was no manifestation of any pathogenic power. The small non-motile bacteria were identical with those named throughout this report as swine-plague bacteria.

II

Several months later the writer, having found the information obtained on this journey quite different from what was expected, undertook another journey in the same State.* As usual the various reports of swine disease found in the papers vanished before the writer's approach, and after much search a herd was found near Sodorus, Champaign County, in which a number of animals had already perished and some were very sick. Two of the latter were killed. In Ko. 1 there were extensive pneumonia and some large ulcers in the large intestine. In No. 2 there were the same pneumonia, a very large spleen, and one ulcer on the valve in the large intestine. Various cultures were made at the time and blood was collected in pipettes which were sealed in the flame. The result of the bacteriological examination was briefly as follows:

From No. 1: The spleen contained only hog- cholera bacteria. The blood (first pipette) hog-cholera bacteria and streptococci. The blood (second pipette) contained only swine-plague bacteria.

From No. 2: The spleen, blood, and pleural cavity each contained swine-plague bacteria.

Sections of the luog tissue of No. 2, hardened in alcohol, showed large numbers of swine-plague bacteria in the alveoli.

With swine-plague bacteria from the pleural tube cultures of pig No. 2 a considerable number of inoculations were made upon smaller animals to determine their pathogenic power as compared with the swineplague bacteria already found. The inoculations were made by injecting definite quantities of bouillon cultures which had been inoculated from single colonies on gelatine plates.

One mouse, one-eighth cubic centimetre subcutaneous! y, dies in 48 hours. One mouse, three-sixteenths cubic centimetre subcutaneously, dies in 24 hours. One mouse, one-twelfth cubic centimetre subcutaneously, dies in 2 days. One mouse, one-twelfth cubic centimetre subcutaneously, dies in 6 days.

In these animals there were no marked lesions. In some the bacteria injected were present in large numbers in the various organs ; in others they were very scarce.

Oue rabbit, oue-eightb cubic centiraetro siibcutanooasly, dies in 4 days. One rabbit, oue-tburtii cubic centimetre subcutaueotisly, dies iu 5 days. Oue rabbit, oue-eiglith cubic ceutimetro subcutaueously, dies iu 3 days.

In the rabbits at the place of iuoculation the subcutis was mncli thickened by i)nrnlent infiltration, and there was more or less hemorrhagic and exudative peritonitis. In the exudate the injected bacteria were very abundant.

Oue pigeon, one-half cubic centimetre subcutaneonsly, dies in 2 days. One pigeon, three-fourths cubic centimetre subcutaneously, dies iu 4 days.

At the place of the inoculation the muscular tissue more or less necrosed. Bacteria not detected in the internal organs.

One guiuea-pig, one-fourtlis cubic centimetre subcutaneously, dies in 6 days with slight local changes and exudative peritonitis and pleuritis.

Oue fowl, one-half cubic centimetre subcutan(;onHly, dies in 5 days.

Oue fowl, 1 cubic centimetre su1)cutaneously, recovered.

In both there was extensive necrosis of the pectoral muscle at the place of inoculation.

The following animals were inoculated by rubbing into the subcutaneous tissue through an incision a loop dipped into a gelatine culture :

One guinea-pig (abdomen) dies iu 5 days; subcutaneous lesion very extensive.

One guiuea-pig (abdomen) dies in 8 days; subcutaneous lesion very extensive.

One mouse (root of tail) dies in 3 days.

One mouse (root of tail) dies in 4 days.

Oue rabbit (ear) dies in 9 days; extensive subcutaneous lesions.

Two pigeons (breast) remain well.

One fowl (breast) remains well.

From cultures of the swine-plague bacteria derived from the blood of pig Xo. 1 two rabbits were inoculated to see if the bacteria from both cases were identical.

One rabbit received one twenty-fourth cubic centimetre bouillon culture; died in 3 days.

One rabbit received a loop of gelatine culture; died in 10 days.

In both there was much local inflammation in the subcutis and peritonitis.

With cultures of the swine-plague bacteria from these two sources a number of pigs were inoculated as indicated in the table :

Pigs.

Dale of inoculation.

Quantity injected.

Soui'ce of culture.

Eemarks.

do fin c. c.

*5

*5"

*3

*5

4*

*5

Dies in 18 days.

Dies in 10 days; generalized jaundice.

Dies in 58 daya.

No 2H9

No 30:t do

Sodoi US, 111

Dies in 9 days ; jaundice.

Dies iu 35 days.

Dies in 8 days ; jaundice.

No effect.

Dies in 11 days ; jaundice.

Dies in 7 days ; jaundice.

No 364 Opt. so IRRfi do

* Subcutaneous.

tinto right lung.

It will be seen that of these ten pigs eight were inoculated subcutaneously with doses ranging from 2J to 5 cubic centimetres of a bouillon culture. Two died from 1 to 2 months after inoculation, the remaining six in from 7 to 18 days thereafter with a x>eculiar disease of the liver and generalized jaundice.

Two inoculated into the lung tissue through the right chest wall remained unaffected.

The liver in these cases was greatly enlarged and so firm that when removed from the bodj' there was no change of form. There was no obstruction to the flow of bile in the bile ducts. The disease of the liver tissue itself was shown in sections of cases 289 and 375 to be due to inflammatory foci within the lobules. In some of these foci the parenchyma cells were still visible, but very feebly stained ; the trabecular arrangement was destroyed j the nuclei of the cells very much shriveled or absent. In other foci the i)arenchyma was replaced by numerous round cells. From these observations it would seem that the disease consisted of necrosis of a mass of hepatic cells followed by round cell infiltration. These foci varied in size from one-eighth to one-half the area of the lobule. Almost every lobule was affected, either several small areas or one large area of disease being present in each, situated usually near the periphery. In No. 375 there was also very extensive cellular infiltration beneath the capsule.*

That the disease was induced by the inoculation can not be very well denied in view of the facts in the case. The animals used were from four difl'erent lots purchased from four diflerent owners.t No other animal in these lots died with these lesions of the liver. The inoculations must, therefore, be considered as the direct cause of the fatal result.

These experiments are in so far remarkable as future subcutaneous inoculations with swine-plague bacteria from other sources, with one exception, produced no effect. 1 have not observed this disease. since the time these experiments were made. The only explanation which can be made is that these varieties of swine-plague bacteria had a slightly different pathogenic power which manifested itself in the manner described.

* Much ill-considered criticism has beeu leveled at these expcrimeuts and results by F. S. Billings, and they are, therefore, presented again simply to show the imfouuded character of these criticisms. While the term cirrhosis used in the earlier reports may not have exactly expressed the diseased condition of the liver, it should also be remembered that the held of comparative patliology is not sufficiently developed to aid us in choosing terms or in finding certain diseases already described and named.

tNos. 287-294, bought June 1, 1886, when 8 weeks old, from Mr. M. ; Nos. 329-335, bought Aug. 27, 1886, when 8 weeks old. from Mr. B. ; Nos. 303-367, bought Oct. 18, 1886, when 8 weeks old, from Mr. J. ; Nos. 368-382, bought Oct. 18, 1886, when 8 weeks old, from Mr. J. F.

TIL

Toward the close of 1880* Dr. Paaren sent to the Bureau portions of lungs from Oerro Gordo Oounty, Iowa, These i)ortions indicated consolidation of the lung tissue with necrotic foci and exudative pleuritis. By inoculation into mice and rabbits swine-plague bacteria were obtained, which, reinocnlated in pure culture, produced death within 24 hours. The bacteria, very abundant in the internal organs, showed distinctly the polar stain. f They did not diUer in any respect from the bacteria found in Illinois, excepting in their greater virulence on the smaller experimental animals. Two pigs inoculated subcutaneously with' 5 cubic centimetres each did not manifest any signs of disease.

IV

In February of 1887 an outbreak of swine disease came under observation which showed conclusively the transmissibility of the lung disease and the bacteria which are the cause.

The disease was associated in every case with pneumonia and pleuritis of a more or less severe character. In the course of the disease caseation of the involved lung tissue was frequently observed. Intestinal lesions of a kind hitherto observed but once before^ were present in the earlier cases. These investigations have been criticised by F. S. Billings, if his statements deserve the name of criticism, because, in addition to the swine-plague bacteria found in almost every case, hog-cholera bacilli were detected in the later cases. It is difficult to discover from his statements which of the two bacteria he objects to. His own report leaves us wholly in the dark which kind he himself has found in Nebraska, owing to the ambiguous manner in which the bacteria found by him have been described. We may therefore pass over these criticisms and briefly summarize the investigations§ which have since been confirmed by much more extended ones.

On January 31 a small number of pigs were purchased from a farm adjoining the Experiment Station for the purpose of testing the effect of different cathartics on the healthy pig. The animals had been purchased from this farm because no disease had existed there for several years. These pigs (Nos. 402-406, inclusive) were put in a pen by themselves. On the following day one (No. 400) was found dead with extensive ulceration of the large intestine, but no lung disease. This occurrence of course spoiled the entire experiment as i^lanned. The disease was regarded as hog cholera by me, although I did not examine the t For the meaniug of tliis expression, see p. 85. t Report of the Bureau for 1886, p. 06.

sS For a full account of the autopsy notes and bacteriological examination, see report of the Bureau for 1887, p. 86.

animal or make cultures, being engaged in other work at the time. Another fact which led to the supposition that this disease was different from the disease which appeared later in the other animals of this lot was told by the owner. Nos. 405 and 406 were the only pigs which had not been confined in pens, and which, therefore, may have been exposed to infection on the farm which did not reach the i^enned animals. At the time No. 400 died (February 1), the other animals appeared well. Some of these were distributed into small pens by themselves and fed different doses of cathartics. Meanwhile no other animal of this lot died until 15 days later, when 403 died. The following table gives information concerning the rest:

Pigs.

Date of death.

Remarks.

Feb. 1 ] Intestinal ulcers.

Feb. 16. .. Veutral lobes of liiiifrs diseased : croupous iuflamiiiatiou of large intestine. Feb. 18- .. Extensive pneumonia and pleuriiis ; croupous inflammation of large intestine. Feb. 19 .. Slight pneumonia ; croupous inflammation of large intestine. Not afl'ected.

As regards the bacteriological examination the following may be said :

No. 406. None made because disease supposed to be hog cholera. No. 403. None made for same reasoQ.

No. 405. Swine-plague bacteria found in lungs; other organs not examined. No. 402. Bouillon cultures made from pleural shreds, spleen, liver, and blood. Gelatine cultures made from blood and liver.

Nearly all the cultures from No. 402 contained a large spore-bearing bacillus which I have frequently found since then in cases of swine disease having hemorrhagic lesions. Cultures from the liver and blood contained also swine-plague bacteria which were isolated by rabbit inoculation.

It will be noticed that in the later cases, Nos. 403, 405, and 402, the large intestine was the seat of a peculiarly intense inflammation, accompanied by the exudation of circumscribed masses of fibrin easily lifted away from the mucosa, leaving a paler, slightly depressed spot showing no necrosis of tissue. In the rectum this exudate formed a continuous sheet also easily removable.

It might be claimed that the feeding of a dose of aloes or salts may have caused this peculiar intestinal inflammation. This claim, however, is effectually disposed of by case No. 407. This animal, one of the same herd, had not been taken from the neighboring farm. It was found dead February 22, and brought to the Station for examination. The notes of this case are reproduced because it must be considered the most trustworthy of all.

No. 407. Pig of medium size, white ; skin of abdomen, chest, neck, and back deeply reddened. Fat abundant, slightly reddened along" the linea alba. Superficial inguinal glands slightly enlarged ; spleen dotted with elevated blood-red points.*

* These points are found in .spleens of healthy swine.

stomach ami (liiodouum uormal, tlio latter bile-staiuod. In ileiiiii Pcyor's patches are visible as <froai»s of small, dark dots ; uo swelling. Mucosa of c;ecam and upper colon of a dirty blackish color, probably pigmented. A few hajmatomata beneath mucosa. Besides the ditt'use pigmentation the mucosa is siiriukled with isolated or conflueut masses, about one-eighth to one-fourth inch in diameter, of a dirty grayish-yellow color, loosely adherent to the membrane. When pulled away a slightly depressed surface is exposed. Much of this mass can bo easily removed by simply moving the scalpel over it. There are several ulcers in the caicum with decided loss of substance. The patch of mucous glands at the base of the valve is also converted into an ulcerated mass. Lymphatic glands in abdomen slightly swollen and reddened. Kidneys deeply reddened to tips of papillic.

On opening the thorax the lungs did not collapse, and a rather disagreeable odor was perceived. As in No. 405, the ventral and cephalic lobes of both lungs were consolidated. The hepatized regions were very hard to the touch, bright red, with yellowish points sprinkled in regularly. (See Plates III and iv.) The right lungwas adherent to chest wall over the hepatized portion. A whitish, spongy membrane was interposed, about one-eighth to one-fourth inch thick, inclosing a small quantity of turbid liquid. Ou removing the lungs the membrane remained adherent to the pulmonary pleura, and was removed with difficulty. A portion of the diaphragm was also firmly attached. The left lung adhered firmly to the chest wall in two places, where it was consolidated. The costal pleura was deeply reddened, owing to the injection of a close net-work of minute vessels. Trachea and bronchi filled with whitish foam.

On section, the consolidated region is sharply but irregularly marked off from the normal tissue, very consistent and slightly elevated. The color varies from a bright red to a grayish red. In all, minute grayish points are present one-twelfth inch in diameter, about the same distance apart, and of a hazy outline. The smaller bronchi are filled with a purulent fiuid. In the surrounding lobules in which the disease is more advanced the interlobular tissue is distended with a serous infiltration ; the large vessels are filled with very consistent dark clots. Heart rather large, pericardium free ; right auricle, ventricle, and large veins distended with clots ; small white clot in left ventricle.

Microscopic examination of the lung tissue in cover-glass preparations shows the presence of numerous bacteria with the polar stain in recent lesions ; in older ones they are rare. Other forms are ijresent, but only in small numbers. The pleural exudate was made up of rounds cells, bound together by bundles of fibrin ; it contains few bacteria.

lu transverse sections of the large intestine, where a mass of exudate is still attached, the muscular and submucous layers are intact, if we except a slight cellular infiltration near the base of the crypts. The mucous layer, however, is considerably changed. The surface epithelium, including a portion of the crypts of Lieberkiihn, is no longer distinguishable, but merges without demarcation iuto an exudate several millimetres thick, consisting of leucocytes imbedded in a mesh- work of fibrin, the whole refusing to stain.

Pure cultures of swine-plague bacteria in tubes of gelatine were obtained from the pleural exudate. In each needle track a large number of colonies developed. A piece of false membrane gave the same result. Cover-glass preparations from spleen and liver were negative. Two tubes of beef infusion into which bits of spleen had been dropped remained sterile. Two similar cultures from the liver contained each a large bacillus, evidently of post-mortem growth. The blood from the heart was also free from bacteria, for two tubes of gelatine, each inoculated six or seven times with blood, did not develop a single colony.

A rabbit inoculated in the ear with a bit of lung tissue died within 4 days. There was no swelling or reddening of the ear. Lungs deeply congested (hypostatic?). Immense numbers of swine-plague bacteria in blood, spleen, and liver. Cultures from blood and liver contained the same organisms. A mouse inoculated with a bit of lung tissue succumbed within 2 days. Bacteria very scarce in body. Pure cultures of swine-plague bacteria were, however, obtained from heart's blood.

What is of importance in tliis case and in No. 402 is the absence of hog-cholera bacilli from the internal organs where we wonld certainly expect to find them in this disease. If wo refuse to consider the intestinal lesions as caused by swine-plague bacteria, we have the alternative of assuming the existence of bacteria which produce intestinal disease without penetrating into the internal organs proper.*

Five other cases in this investigation deserve special attention. N'os. 408, 409, and 410 of the same herd still remained on the farm. After the examination of 407 had shown the absence of hog cholera, and the presence in the diseased lungs of swine-plague germs, and the evidence thus far obtained pointed to a different disease caused by the latter bacteria, two pigs, Nos. 359 and 360, were taken from the Station to the farm and penned with the three mentioned to determine whether the disease is readily communicable. This was done February 28. March 5, No. 408 died. March IG the remaining four were taken back to the Station and placed in an unused pen free from infection, so as to be under observation.

Of these four pigs No. 409 died March 20, No. 410, March 29. Of the exposed animals No. 359 died March 24, 24 days after the commencement of the exposure ; No. 360, April 6, 37 days thereafter. Of these four cases No. 360 was not examined. Of the remaining three, hogcholera bacilli were detected in 409 by rabbit inoculation, but not in either 408 or 410, while swine-plague bacteria were found in 408 and 359. Looking over the original notes I am convinced that the number of cultures made from the spleens of 408, 410, and 359 were suflBcient to enable us to exclude the presence of hog cholera from these cases. No. 409 is therefore the only animal from the adjoining farm which was examined in which hog-cholera bacilli were detected. It is likewise strange that in the spleen of No. 408 a bacillus should appear resembling hog-cholera bacillus in many respects, but not identical with it, and producing only supi^uration in rabbits.

The cases which came under observation subsequently, and in which hog-cholera bacilli were readily demonstrated in the spleen, were Station pigs which had been exposed some time ago to the infection of hog cholera. These cases are chiefly valuable in pointing out that the swineplague bacteria are transmitted from animal to animal and associated with lung disease. They may be thrown out altogether, since the source of the hog-cholera bacilli is traceable.

No. 372. Fed viscera of hog cholera case December 24, 1886, in infected pen.

* By " internal organs " I mean those organs which db not come in contact with the air or food, either directly or indirectly. Thus the entire respiratory and digestive tract may be regarded as external, so far as bacteria are concerned.

No. 378. Fed viscera of hog cholera case Ifovember 18, 188<>, in infected pen. Fed viscera of 406 Febrnary 2, in infe(;ted pen.

No. 3913. Inocnlated with swine plague bacteria (Iowa) January 25; placed in the infected pen March 28.

No. 397. Fed viscera of 378 in pen 7 March 24.

In 372, 392, 397, both hog cholera and swine plague bacteria were found. Their presence in the old infected pen or their contact with pigs kept there will account for this double infection.

The facts brought out by this investigation corroborated those already brought out in the investigations of the preceding year. They showed the existence of pneumonia and pleuritis, together with intestinal disease in most of the animals examined, associated with bacteria readily distinguished from hog-cholera bacteria.

They also demonstrated the trausmissibility of the pneumonia to other pigs, and in these pigs the same bacteria were found.

If the lesions of the large intestine, as observed in the early cases, were due to hog-cholera bacilli, why were these bacilli not found excepting in one late case in which there may have been an accidental infection of the rabbit inoculated ? Why were hog-cholera bacilli readily detected in the later cases kept in the infected pen ?

While these investigations do not prove that the swine-plague bacteria were the cause of the intestinal lesions, they also do not seem to show any relationship between these lesions and hog-cholera bacilli. This question of the relation between intestinal lesions and swineplague bacteria will be discussed farther on.*

V

In September, 1888, an outbreak of swine disease near Baltimore, Md., came to our notice. Throe pigs from one herd and one from another herd were examined. The following syno])sis of the cases may be of interest, the full account being given elsewhere. t

Pig No. 1. Broncho-pneumonia; exudate on mucosa of rectum and lower colon ; swine-plague bacteria detected in lungs and rectum ; hogcholera bacilli in si)leen.

Pig No. 2: Three-quarters of both lungs hepatized ; ulcers in ileum and colon; swine-plague bacteria in lungs; hog-cholera bacteria in spleen.

Pig No. 3: Extensive pneumonia and pleurisy; ulceration of large intestine; swine-plague bacteria in lungs; hog cholera bacteria in spleen.

Pig No. 4 : Slight atelectasis of lungs ; ulcers in large intestine ; swine-plague bacteria in large intestine; hog-cholera bacteria in spleen.

Pig No. 3 was taken to the Experiment Station, where it became the starting point of a mixed outbreak of hog cholera and pneumonia.

t Report of the Bureau, etc., 1887-'88, p. 121.

VI

Duriag iJ^ovember, 1888, the writer was directed to make some investigations in Iowa,* where swine diseases at that time were prevailing to a considerable extent. In the vicinity of Mason City pigs from three herds, some distance apart, were examined. The lesions observed were both intestinal and pulmonary. The intestinal lesions, though varying considerably in appearance and intensity, did not differ, on the whole, from those observed in hog cholera. The lung lesions varied considerably in character and extent, from a slight collapse in a single lobe to almost total hepatization, accompanied by exudative pleuritis.

The investigations were limited to post mortem examination and cultures from the spleen. From each spleen small bits of tissue were removed to two tubes of agar. In addition, portions of diseased lung tissue and ulcerated mucous membrane from the large intestine were cut out and transferred to sterile test tubes plugged with cotton wool for inoculation into rabbits. Ten pigs were examined in this manner.

In but one case did the spleen pulp show any bacteria under the microscope, and in this case they were streptococci, tn but one agar tube of the spleen series did anything develop. This was a motile bacillus, resembling the hog cholera bacillus in form, but differing in its growth on agar, in bouillon, and in gelatine, this growth being in all cases more vigorous. Of two mice and one rabbit inoculated, one mouse died in 5 days. The lesions were indefinite and did not point to hog cholera. Moreover, the other mouse and the rabbit remained unafiected.

With particles of diseased lung tissue and mucous membrane from some of these cases a considerable number of rabbits and some mice were inoculated. Of those that died some contained no bacteria of any description. Those inoculated from three cases out of ten died of swine plague since these bacteria were found. A few survived the inoculation.

The nature of this disease was not, therefore, cleared up by these investigations, since the results were not uniform. While in hog cholera the bacilli are present in the spleen, and readily obtained therefrom by cultivation, they were not present in the spleens of these ten cases. As already stated, swine-plague bacteria were obtained from three cases. They were quite virulent, as the inoculations upon pigs show. Thus one pig, which received 9 cubic centimetres of a bouillon culture into the right lung through the chest wall, died within 20 hours of septicaemia, the injected bacteria being present in the spleen in considerable numbers. Another pig, which received a subcutaneous injection at the same time, remained well. Somewhat later two pigs received into the right lung 1^ cubic centimetres and 3 cubic centimetres of a bouillon

* Report of the Bureau of Animal Industry for 1887-'88, pp. 135-145, wLore a detailed account of this work is given.

culture. The one which had received the smaller dose was sick for a time, but recovered. It was killed U months after the inoculation, and both lungs were found everywhere adherent to the chest wall. In the pericardial sac a considerable quantity of pus had collected, in which the injected bacteria were still present, as determined by cultures.

The animal which had received the larger dose became very ill and was killed 5 days after inoculation. At the autopsy were detected partial hepatization of the right lung, with extensive exudative pleuritis and pericarditis.

The two following cases, which have not yet been published, demonstrate very strikingly the virulence of these bacteria. The growth on a number of agar cultures about 9 days old was scraped off and transferred to sterile bouillon until a turbid suspension was obtained. This suspension was prepared because these bacteria multiply very feebly in bouillon, and when the latter is used as the injecting fluid very few bacteria are actually introduced into the body. This turbid suspension was used to inoculate 2 pigs. No. 120 received into the abdomen 2 cubic centimetres; No. 143 into the right lung through the chest wall but 1 cubic centimetre. The inoculation was made March 11, 1889, over 3 mouths after the bacteria had been obtained from the diseased swine.

No. 120. Essex female, 5 months old. Into the right lung through the chest wall, 2 cubic centimetres of above suspension injected with hypodermic syringe, 6 p. ra. March 11. Found dead early next morning.

Subcutaneous inguinal glands partly hemorrhagic. From the cut subcutaneous vessels of right side liquid blood oozes out. In abdomen the solitary follicles of large intestine appear as bright red circular si^ots three-sixteenths inch diameter, as seen from serosa. Spleen slightly engorged.