REPORT OF THE BUREAU OF ANIMAL INDUSTRY. 121 



probable that preventive inoculation either with ptomaines or with 

 attenuated cultures will "be successful. But if there is, in addition, 

 a mechanical element which may overshadow in importance the pto- 

 maine 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 different cultures exposed to the same conditions. This would 

 be a serious hindrance in obtaining vaccinal cultures of uniform 

 strength should this method ever prove 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 

 multiply 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 

 suspicion of impurities, but tests on gelatine plates showed that the 

 suspicion was unfounded. These experiments will be continued on 

 rabbits and pigs under similar conditions to determine whether any 

 immunity can be produced by this method. 



INVESTIGATIONS OF AN OUTBREAK OF INFECTIOUS SWINE DISEASES 

 NEAR BALTIMORE, MD., SEPTEMBER, 1888. 



The practical difficulties in connection with the solution of the 

 problem of infectious swine diseases has been pointed out, in the an- 

 nual report of the Department of Agriculture for 1887, to be due to 

 the existence of two diseases producing lesions of the intestinal tract 

 which shade into one another and are therefore not distinguishable 

 by the naked eye. The presence of the specific microbe seems to be 

 the only final test. As a rule, however, swine plague is primarily a 

 disease of the lungs, secondarily of the digestive tract, while we 

 have invariably found hog cholera a disease of the intestinal tract 

 and more particularly of the large intestine, with unimportant lesions 

 of the lungs very likely not due directly to the hog cholera virus. 

 This difference may often serve as a guide when bacteriological ex- 

 amination can not be made, but even this is frequently misleading. 

 The existence of extensive lung disease as the result of the polar- 

 stained swine plague organism does not exclude the simultaneous ex- 

 istence of hog cholera. It is not an uncommon thing to find the le- 

 sions of both diseases as well as the microbes which produce them in 

 the same animal. The following cases illustrate this condition of 

 things very well. Several pigs from two separate herds near the city 

 of Baltimore, Md., which were affected with some infectious malady 

 were examined and both hog cholera and swine plague germs were 

 found in the same animal. One of these animals was transferred to 

 the experimental station at Washington, and there gave rise to an 

 epizootic of both diseases. The swine plague soon gave way to the 

 hog cholera, however, and later on lung disease was but a secondary 

 element in the disease, hog cholera persisting with variable severity 

 for months after. 



In the herd which contained the following pigs the disease broke 

 put four weeks ago and was very likely due to the introduction of 

 infected swine by purchase. 



September 10, 1888. A small shpat (No. 1) from this herd was 

 seemingly very ill. Flanks tucked in, hind portion of body swaying 

 and tottering when the animal moved. It was killed by cutting its 

 throat. 



