CLINICAL EVIDENCE OF VALUE OF SERUM 441 



them became ill as a result of close association with the treated 

 animals. 



This experiment also offers proof of the desirability of using 

 the double method of treatment when placing hogs in an infected 

 feed lot, rather than depending upon the entrance of the virus of the 

 disease through the regular channels of infection. If in this case 

 the serum alone had been used, and dependence placed upon the 

 animals taking up the necessary germs from the feed lot to result in 

 the training of the cells in the method of manufacturing germ- 

 fighting bodies in order to establish a permanent protection, the 

 results would have been disappointing. The only certain method 

 of getting a permanent protection against the disease is by inject- 

 ing both the virus blood and the serum, unless the animal already is 

 infected with the germs, as shown by a high fever or other signs of 

 commencement of the disease. 



Herd Number Nine. — The herd which formed the basis for this 

 ninth experimental test with serum was located in the northeast 

 quarter of Section 2, Union Township, Story County. This herd 

 was located about 20 rods from the herd which has been described 

 as Herd Number Five in this list of experiments. At the time 

 the herd was first seen, October 10, 1907, the hogs were already 

 infected. The disease had most likely spread to this herd from 

 Herd Number Five, just mentioned, or from other disease-infected 

 farms, of which there were quite a number in the immediate neigh- 

 borhood. 



When first observed by the United States veterinarians there 

 had been no deaths in the herd, but 2 of the shoats had been sick 

 for a couple of days with symptoms which were unquestionably 

 those of cholera. The balance of the hogs were still apparently 

 healthy. 



There were in this herd at the time 35 shoats and 2 old sows. 

 Thirty of these shoats, including the 2 that were sick with the dis- 

 ease, were injected, each receiving 20 c.c. of serum and 1 c.c. of virus 

 blood. The dose of the virus blood given in these animals was cut 

 down to 1 c.c, on account of the fact that cholera infection was 

 already present. The temperatures met with in these hogs are not 

 reported. The 2 old sows were also injected, each receiving 40 c.c. 

 of serum with 1 c.c. of virus blood. 



