CLINICAL EVIDENCE OF VALUE OF SERUM 495 



lot from other sources, in which cases the unprotected animals 

 would naturally fall victims. 



These experiments seem to offer a suggestion, at least, that the 

 virus which is injected into the body of the hog in giving the simul- 

 taneous treatment must be so acted upon by the tissue cells of the 

 injected animal and the protective bodies of the serum as to neu- 

 trahze entirely its disease-producing qualities. As a result, when 

 it leaves the body of the hog so treated it is no longer a disease- 

 producing virus, but is, instead, a neutral substance, entirely in- 

 capable of producing harm. It has worn out its disease-producing 

 powers in the battle against the cells of the animal it sought to 

 attack and is now harmless. 



It is possible that in some herds hogs are found that are more 

 susceptible to the effects of the cholera germ, and who may suffer 

 mild symptoms of hog-cholera even when given an average pro- 

 tective dose of serum in connection with the virus. These animals 

 are so easily influenced by cholera virus that they need more than 

 the ordinary amount of protection. These same cases of mild 

 cholera may discharge disease-producing germs in their urine and 

 feces, and might infect a feed lot so as to cause an outbreak 

 of cholera in unprotected animals. Such cases are very infre- 

 quent, and especially so if a liberal dose of a powerful serum 

 is used. 



Herd Number Thirty-eight. — This herd was located in the 

 southwest quarter of Section 26, Franklin Township. The animals 

 of this herd were all pure-bred Duroc-Jerseys, and consisted of 

 old hogs and spring shoats of various sizes. When treated the 

 animals were all in apparently good health. Treatment was given 

 on November 9, 1907. 



There were 31 spring gilts in this herd, weighing on an average 

 from 100 to 200 pounds. These each received from 30 to 40 c.c. of 

 serum, in accordance with their weight, and an accompanying 

 injection of 1 c.c. of virulent blood. Sixteen young boars from the 

 same litters, and weighing about the same as the gilts just men- 

 tioned, were treated with the same size dose of serum and a 1-c.c. 

 injection of virus. One old boar was injected with 50 c.c. of serum 

 and a 1-c.c. dose of virus blood. Sixteen old sows, weighing from 

 300 to 400 pounds each, were injected with 50 c.c. of serum and 1 



