112 HOG CHOLEBA 



The finished product. It has already been 

 shown that all serum sent out is, or should be, 

 subjected to carefully controlled tests in which it 

 is required to protect laboratory pigs in much 

 smaller doses than would be administered to like 

 animals in the field. The protective defibrinated 

 blood, called anti-hog-cholera serum, is the basic 

 preparation from which all the more or less re- 

 fined products now on the market take origin, and 

 when it is prepared with careful technique it is in 

 the original state a highly effective and safe im- 

 munizing agent. It may or may not be sterile. ' 



Clear serum is "bloody serum" minus blood 

 corpuscles. It is prepared from the protective 

 defibrinated blood by various combinations of 

 processes which, individually considered, include 

 precipitation of the red blood corpuscles with 

 navy bean extract, centrifuging, and filtering 

 through various materials. Heat, 60 C., for one- 

 half hour, is applied, which kills some contaminat- 

 ing organisms that may be present. An impres- 

 sion seems to prevail that all clear serum is sterile, 

 but this is not true, for it is not necessarily sub- 

 jected to temperatures or other treatment which 

 will kill or remove all living bacteria. 



The comparative merits of clear and "bloody" 

 serum are the subject of much controversy, but as 

 is true of other things of like nature, individual 

 methods are the deciding factor. Clear serum, 



