CLINICAL EVIDENCE OF VALUE OF SERUM 427 



posed to infection not only from the virus which remained in the 

 infected feed lots, but also by direct contact with the sick herd and 

 with their virulent bowel and urinary discharges. 



The date on which these animals were injected and placed in the 

 infected pens was September 9th, Ten days later the 10 that had 

 been injected with serum were still in good condition, but the 3 

 check pigs which were not protected by serum were already begin- 

 ning to manifest symptoms of the disease. The herd was again 

 visited on September 25th, and at this time one of the check ani- 

 mals was dead. The other 2 checks were in a very sick condition, 

 and exhibited all the usual symptoms of hog-cholera. Five days 

 later, September 30th, all 3 of the check pigs were dead. Thus, 

 within a period of twenty-one days the 3 healthy shoats which had 

 not been previously exposed to the disease had contracted cholera 

 and all had died. Of the serum-injected animals all remained well 

 throughout the experiment except one, which developed a slight 

 soreness of the eyes. This was perhaps entirely accidental and had 

 nothing whatever to do with the use of serum. Not only did these 

 shoats remain healthy throughout the course of this experiment, 

 but they did not afterward contract the disease in so far as is known, 

 later observations showing that all 10 remained well and thrifty. 



This experiment brings out some very interesting facts about 

 cholera which are worthy of noting. 



It proves conclusively that the disease will attack healthy 

 animals which have not been previously exposed if they be placed 

 in an infected pen or brought in contact with others that are suffer- 

 ing from the disease. 



This experiment serves also to show the short incubation 

 period of the virulent types of hog-cholera, and especially so in 

 young shoats. All 3 of the untreated animals were showing 

 symptoms of the disease at the end of ten days, and so rapid was 

 the course of the outbreak that the entire herd of untreated hogs 

 was wiped out in less than three weeks from the time of exposure. 



In connection with those treated, it is indeed a most inter- 

 esting observation that while all 3 of the untreated animals 

 quickly sickened and died, not one of the 10 that were treated 

 even became seriously ill. The sore eyes which were developed 

 by one of them were no doubt entirely due to some other cause 



