436 DISEASES OF SWINE 



lency of cholera in small pigs, all but 4 of them being carried off 

 by the disease. 



(4) It is also interesting to note in this case that the 2 

 animals which made an apparent recovery from the disease re- 

 mained unthrifty and practically valueless. This is usually the 

 case. Animals which show severe symptoms of cholera and 

 recover are usually left in an unthrifty condition and are rarely 

 profitable to keep. In the majority of cases it is more economic 

 to destroy the runts than to bother with keeping them. 



(5) In this herd the serum alone was used, as there was evi- 

 dence that the animals already were infected. In this case it 

 was thought unnecessary to inject any virus, as the hogs already 

 had been inoculated with virulent material which had been ab- 

 sorbed by contact with infected animals. In this case the immunity 

 conferred was of the permanent type in most of these animals, 

 just the same as if they had received the simultaneous or double 

 treatment. This is the rule which should be followed : Give serum 

 alone where the animal is already infected as shown by actual 

 symptoms of the disease or presence of temperature above 104° 

 or 105° F. On the other hand, in treating exposed herds, where 

 there is no evidence of the actual presence of the disease, give the 

 simultaneous or double treatment. The double treatment should 

 also be given in infected herds to those that show no evidence 

 of cholera and have a normal temperature. 



Herd number six in this series of experimental inoculations 

 was located in the northeast quarter of Section 3, Grant Town- 

 ship, and probably became infected from a diseased herd which 

 was being fed just across the road. This farm was first 

 visited on October 5, 1907. At this time there was one shoat 

 sick, which had been noticed unwell for three days. The ani- 

 mal was not markedly sick, but was noticeably droopy and 

 was not eating well. Another hog was also seen to be slightly 

 off feed, but the remainder of the herd showed no visible symptoms 

 of disease. All of the animals, however, sick and well, were run- 

 ning together in the same feed lot and pasture, so that the healthy 

 ones had all undoubtedly been exposed to the infection, and 

 many of them were in various stages of the period of incubation. 



In this experiment 12 shoats, ranging in weight from 40 to 



