70 MODERN BIOLOGIC THERAPEUSIS 



which inhibits clotting, so that a separation of 

 plasma from corpuscles can be accomplished. 

 This plasma is protected with chloroform and 

 placed in cold storage until refined. 



The above description in its essential details 

 applies to the production of Tetanus Antitoxin 

 as well as to Diphtheria Antitoxin; also to the 

 production of the antibacterial sera, except 

 that in the latter case the blood is drawn in 

 such a way as to obtain serum instead of the 

 plasma. 



Standardization The therapeutic use of the 

 antitoxic sera is facilitated by the fact that 

 they can be standardized according to their 

 power of neutralizing known quantities of a 

 corresponding toxin, and by expressing their 

 value numerically in antitoxic units. Normal 

 guinea-pigs weighing 250 grams are used in 

 the test. Neither the guinea-pigs themselves 

 nor their mothers can have been used previ- 

 ously for testing diphtheria toxin or antitoxin; 

 because it has been shown that a certain degree 

 of immunity may be present in guinea-pigs 

 that have previously been used for testing 

 toxin or antitoxin, and in guinea-pigs whose 

 mothers have been injected with toxin and an- 



