CLINICAL EVIDENCE OF VALUE OF SERUM 493 



various sizes were left untreated to serve as checks. The old 

 sow finally recovered, and, as there was no further sickness either 

 among the treated or untreated animals, it must be concluded that 

 hog-cholera did not really exist in the herd. 



This is another example of the fact that not every disease of 

 hogs showing loss of appetite, droopiness, and cough or diarrhea 

 is hog-cholera. It may be stated, however, that in over 90 per 

 cent, of such cases hog-cholera will be found to be the correct 

 diagnosis, and so seldom is any other disease present that it is the 

 part of wisdom to administer the serum at once, without waiting 

 for an animal to die in order to make sure of the diagnosis. 

 If the disease is not cholera, no damage will be done by giving 

 the serum, and if cholera is really present every hour that the 

 administration of serum is delayed just means that much of an 

 increase in the number of animals that cannot be saved. 



There is a little subsequent history attached to this last- 

 mentioned herd that is of particular interest. The owner of these 

 animals sold them at public sale the following spring, and some of 

 them were purchased by a man who had had hog-cholera on his 

 farm. These animals were taken home and placed in the infected 

 feed lots, where they very promptly contracted hog-cholera and 

 died. 



This gives us again an example of the fact that the protection 

 given by the administration of the serum alone is only temporary. 

 It is only when the virus is used, or when it is already present in 

 the animal at time of injection, that a permanent immunity is ob- 

 tained. The great advantage of the double method of treatment 

 Hes in this very fact, that the animals after treatment can be re- 

 moved to another farm where hog-cholera is present, or has been 

 present, and can be placed in the disease-infected feed lots without 

 danger. If they have been double treated with a virulent virus 

 blood there is no danger, as the protection derived from this treat- 

 ment lasts as long as the animals live. On the other hand, where 

 single treatment is used, and months afterward the animals are 

 moved to an infected feed lot, sickness and death are sure to 

 follow. 



Herd Number Thirty-seven. — The thirty-seventh herd treated 

 in the series was located in Section 21, Washington Township. 



