BUREAU OF ANIMAL INDUSTRY. 633 



spleen of No. 3. Nor was it present in a pipette of blood obtained 

 from the heart. The autopsy notes will indicate that the intestinal 

 lesions were limited to a single patch of ulceration at the base of the 

 valve. Whether this was due to hog-cholera cannot be said. Never- 

 theless the absence of the bacterium of hog-cholera from the internal 

 organs in chronic cases, or its great scarcity, has been a matter of 

 common observation in our investigations of this disease. The dis- 

 ease is in fact over, and only the lesions remain. It resembles in this 

 respect typhoid fever in man. 



The presence of another microbe in this animal, however, even 

 more virulent in its effects upon animals than the bacterium of hog- 

 cholera, gives it a peculiar interest, as indicating the existence of two 

 totally distinct diseases in the same herd and even in the same animal. 



To illustrate the negative results often obtained in this disease it 

 seems advisable to give the post mortem notes of another case of 

 genuine hog-cholera observed at a place but a few miles from the 

 herd from which Nos. 1 and 2 were taken. In this herd the animals 

 were slowly dying of a chronic malady lasting weeks. None of those 

 alive seemed very ill excepting one, which, when incited to run, would 

 move a short distance and then lie down. Yet when an attempt was 

 made to catch it it showed considerable strength, scarcely warranted 

 by the extensive lesions found at the autox)sy. It was killed by a few 

 blows on the head. The following facts were noted down: 



The superficial inguinal glands very large and of a pale red. In the 

 peritoneal and pericardial cavity a small quantity of serum; blood clots 

 readily: lungs normal. In tlie csecum the mucous membrane is con- 

 verted into a continuous yello"wish necrotic layer. The remaining 

 portion of the large intestine, containing but little food, is studded 

 with isolated ulcers from l'^"" to 2"" (i to {- inch) across, showing on the 

 surface concentric bro^*n.ish and yellowish rings. These ulcers are 

 visible as opaque whitish patches under the serous coat, which are 

 surrounded by zone of newly formed injected vessels. The iilcera- 

 tion, being thus deep, indicated a disease of some weeks' d.uration. 

 These lesions accorded very well with those observed at the Experi- 

 mental Station. 



The spleen, which was preserved in a sterilized bottle, contained no 

 germs ^dsible on cover-giass preparations. A pipette of blood was 

 sterile, neither liquid nor solid cultures manifesting any growth after 

 inoculation. Of about six tubes of gelatine, each containing a bit of 

 spleen tissue, all but two remained permanently sterile. One of 

 these contained a feebly growing motile bacillus, harmless to both 

 mice and rabbits. The other contained a liquefying microbe not 

 further examined. 



EXPERIMENTS DIRECTED TOVv'ARDS PRODUCING IMMUNITY. 



On page 219 of the Second Annual Report of the Bureau of Animal 

 Industry an account is given of an experiment demonstrating the 

 very important fact that pigeons may be made insusceptible to the 

 strong virus of hog-cholera by the subcutaneous injection of liquid 

 in which the bacteria had multiplied and had afterwards been de- 

 stroyed by heat. 



In order to confirm the remarkable result there obtained a second 

 experiment was tried in the same waj'". Tliree pigeons were inocu- 

 lated at three diif erent intervals indicated in the table below with 

 l'" of heated culture liquid in which the bacterium of hog-cholera 



