470 DISEASES OF SWINE 



with the exception of one of the 100-pound shoats. This animal 

 appeared to have considerable resistance against the disease, as he 

 did not even show signs of being sick. 



The animals that died showed the usual symptoms of hog- 

 cholera, but, as this herd was a considerable distance from the 

 Ames station and an even greater distance from the other herds that 

 were under observation, it was impossible for the men engaged in 

 the experimental work to make a return trip and open up the bodies 

 of any of the dead animals in order to make sure that the disease 

 really was cholera. 



None of the old hogs that had received the double treatment 

 became sick. Out of the 15 shoats which were injected with 30 c.c. 

 of serum and 2 c.c. of virulent blood there were 8 that became sick. 

 Three out of this 8 finally died. The other 5 recovered. In con- 

 nection with these 8 treated animals, the owner reports that the 

 symptoms they had were not those of hog-cholera, and he did not 

 believe that they really died from cholera. It is unfortunate, on 

 this account, that the station experts were unable to make a second 

 trip to the farm at this time and open up the bodies of some of these 

 dead animals for the purpose of definitely deciding whether or not 

 the cause of death was hog-cholera. In view of the fact that the 

 animals appeared to have something wrong with them at the 

 time they were treated, it would seem very probable that there 

 was some other disease than cholera present which accounted for 

 the deaths in the treated animals. 



Of the 14 head of small shoats and pigs which were injected 

 with serum alone, all died but 1. This is explained by the fact 

 that the disease did not make its appearance in the herd until 

 nearly a month after the date on which the serum was injected. 

 The protection given where the serum alone is used is only tem- 

 porary, and begins to disappear at the end of three or four weeks. 

 This was the case here. At the time the disease invaded the feed 

 lot the serum had lost its protective power in these animals, and 

 as they had had no virus blood to stimulate in their system the 

 formation of germ-fighting bodies they were left unprotected. 



In the case of the old hogs that were injected by the double 

 method, the protection created here was permanent, and they were 

 able to pass through the outbreak without showing any signs of 



