114 HOG CHOLERA 



from, or superior to, the other. Carotid-bled se- 

 rum is a mere "talking point. " Some laborato- 

 ries situated near stockyards can produce it more 

 cheaply than they can produce the tail-bled prod- 

 uct, and this fact, rather than considerations 

 based on the quality of the product, explains their 

 preference for carotid-bled serum. Both products 

 pass like tests before being released for use. 



The keeping qualities of anti-hog-cholera 

 serum vary with different lots, and with various 

 methods of preparing and storing. Bureau of 

 Animal Industry regulations place the expiration 

 date at two years from the time the first bleeding 

 in a particular lot takes place, and subject to satis- 

 factory retest at the end of two years, another 

 year may be added. Our own preference is for a 

 shorter period, for in one or two instances we 

 have known serum to fall away in potency before 

 it was two years old. 



Serum should always be stored in a dark, cool 

 place. According to a limited number of tests 

 conducted by Kernkampf, freezing does not in- 

 jure it, but temperatures below the freezing point 

 are not desirable. A temperature between 40 

 and 55 F. seems to be most favorable. After the 

 seal on a bottle has been broken and a portion of 

 the serum removed, the remainder should be used 

 in the course of a few days, or discarded. It is 

 always well to open the bottle out of doors, if all 



