BLOOD-SERUM. 125 



supplanted the method of Koch. These modifications 

 comprehend both the source and the manner of obtain- 

 ing the serum, and the method of subsequently steriliz- 

 ing it. In the first place, it is becoming more and more 

 the custom to obtain serum from horses, not because it 

 possesses any nutritive advantages over that from 

 bovines, but because it can, in some large cities at 

 least, be easily obtained from the laboratories in which 

 horses are used in the production of antitoxins. In 

 these places the blood is drawn direct from the jugular or 

 some other large vein by means of a trocar thrust through 

 the skin into the vessel. The result is that the animal 

 is not injured, the blood is obtained in a cleanly manner, 

 and when due precautions are taken it is almost free 

 from bacterial contamination, so that the sterilization 

 of the serum obtained from it offers little or no diffi- 

 culty. For particular purposes blood and serum are 

 often obtained in a somewhat similar manner from other 

 animals. 



For the sterilization of serum the method now in 

 vogue is that of Councilman and Mallory. Its popu- 

 larity is due to the following facts : by it the serum is 

 more quickly and easily prepared ; rigid precautions 

 against contamination during collection of the serum are 

 not so necessary ; and the resulting medium, while not 

 transparent or even translucent (points aimed at in the 

 original method), fully meets all the requirements. 



The special points in the method are : the serum is 

 decanted into test-tubes as soon as obtained ; it is then 

 firmly coagulated in a slanting position in the dry-air 

 sterilizer at from 80 to 90 C. ; it is then sterilized in 

 the steam sterilizer at 100 C. on three successive days, 

 as in the case of other culture-media. It may then be 



