426 DISEASES OF SWINE 



in sick animals will save a large percentage of them. It has also 

 been found that contact infection cannot always be depended upon, 

 and, accordingly, the better plan is to give the double treatment in 

 every hog that does not show by presence of fever or other signs 

 that it is already sick. This applies with equal force to infected 

 or exposed herds. 



I wish again to acknowledge my indebtedness to the official 

 report of Dr. Niles for the basis of this experimental evidence of 

 serum injections. I give these in preference to results reported by 

 other men or myself on account of the great importance of this 

 series of investigations in establishing the serum treatment of 

 cholera on a firm basis. 



Herd Number One. — This first herd which was used in the 

 carrying out of the investigation experiments of Drs. Niles and 

 Dorset was located on the northwest quarter of Section 9, Nevada 

 Township, Story County, Iowa. This farmer had had a herd of 

 100 head of hogs at the beginning of the season. Cholera of a most 

 virulent type made its appearance in the herd, and at the time the 

 farm was visited by the United States veterinary experts 90 out of 

 the total of 100 head had been lost. The postmortem evidences 

 revealed by examination of the carcasses of several animals recently 

 dead of the disease were typically those of cholera. Sick shoats 

 remaining among the 10 living also showed the usual symptoms 

 of cholera. 



It was evidently too late here to do any great amount of good 

 for the owner of this herd, but arrangements were made with him 

 to carry out an experiment on his farm, to demonstrate the effi- 

 ciency of serum as a preventive agent against hog-cholera infection. 

 For the purpose of carrying out this experiment 13 small shoats, 

 averaging in weight from 35 to 40 pounds, were purchased. These 

 animals were bought from a herd which was perfectly healthy, and 

 the animals had not, so far as known, been in any way exposed to 

 hog-cholera. 



Ten of these animals were injected with hog-cholera serum, each 

 shoat receiving 20 c.c. of the serum. The other 3 were left 

 untreated, to serve as checks. The entire 13 hogs were then 

 placed in the infected pens, together with the sick animals which 

 remained from the original herd. In this manner they were ex- 



