MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 86 1 



button-like ulcers in the large intestine. Immunity in hogs which 

 recover. 



The etiology of hog cholera has long been the subject of scientific 

 controversy, but it is now generally acknowledged that the cause of 

 this disease is a filtrable microorganism which exists in the blood, 



FIG. 181. Haemorrhagic points on kidneys of hog-cholera hog. (Original.) 



the internal organs, and the urine of infected hogs. The fact that 

 this disease is caused by a filtrable microorganism was demonstrated 

 as follows:* 



The blood serum of hogs infected with hog cholera acquired in the 

 natural way is very infectious for non-immune hogs, the disease being 

 readily transmitted by the subcutaneous injection of small amounts. 

 The disease, produced by this subcutaneous injection is identical in all 

 respects with the disease as it occurs in nature. If, now, this infectious 



* Bulletin 72, Bureau of Animal Industry, U. S. Dept. Agriculture, 1905. 



