PREPARATION OF ANTI-HOG-CHOLERA SERUM 113 



if not subsequently diluted may be administered 

 in somewhat smaller doses than can "bloody" 

 serum, it is free from extraneous matter which 

 has no immunizing value, and all other things 

 being equal it is more likely to be sterile. On the 

 other hand it usually becomes cloudy on standing, 

 its keeping qualities and continued potency after 

 heating, so often emphasized, are yet to be fully 

 established, and it is more expensive than the 

 "bloody" serum. "Bloody" serum contains cor- 

 puscles which are of no value in immunizing, and, 

 like the clear serum, if it is not carefully prepared 

 it may also contain excessive numbers of bac- 

 teria. On the other hand it is not subjected to 

 complicated processes which invite error in tech- 

 nique, and it can be prepared much more cheaply, 

 per immunizing unit, than clear serum. 



Disregarding entirely the form of the finished 

 product, the test, conscientiously applied and 

 skillfully interpreted, is the swine breeder's guar- 

 antee of safety to his herd. Thus either clear or 

 "bloody" serum, carefully prepared, is a safe and 

 effective immunizing agent; neither, carelessly 

 prepared, will produce the results the breeder and 

 his veterinarian have a right to expect. 



The relative merits of tail-bled and carotid-bled 

 serum have also been the subject of much absurd 

 controversy, for no scientific evidence has ever 

 been submitted to prove one product different 



