466 



INFECTION AND RESISTANCE 



In carrying out the standardization the L + dose of 'the toxin is 

 used, but, unlike diphtheria standardization, in this case the L+ 

 dose means an amount of toxin which will kill a guinea pig of 350 

 grams in four days, although united with 0.1 unit of antitoxin (it 

 must be noted that the L+ dose in this case is measured against one- 

 tenth unit of antitoxin rather than against 1 unit, as in the case of 

 diphtheria. 



In determining the value of an unknown antitoxin, mixtures are 

 made, each containing the L_|_ dose of the toxin and varying quan- 

 tities of antitoxin. As in diphtheria measurements, the various in- 

 jection volumes are brought to 4 c. c. with salt solution, and are then 

 injected subcutaneously into guinea pigs of about 350 grams. The 

 table given below is taken from the Bulletin of Rosenau and Ander- 

 son. 



In this experiment 0.0015 equals 0.10 antitoxin unit. 



ANTITOXINS AGAINST SNAKE POISONS 

 (Antivenin) 



Antitoxins against snake poisons have been produced by a num- 

 ber of different workers, but the subject has been most extensively 

 studied by Calmette. As early as 1887 Sewall 40 succeeded in in- 

 creasing the resistance of pigeons to snake poison. Later Calmette 

 and Physalix and Bertrand independently succeeded in producing 

 immunity in rabbits and guinea pigs with the poison of the cobra. 

 The serum of animals treated with snake poisons gradually acquires 

 antitoxin properties, but the process of immunization is not a simple 

 one, and considerable time is needed for the immunizations. 



Snake poisons, as we have seen, have attracted considerable atten- 

 tion because of their peculiarities in being antigenic and yet differ- 

 ing in heat resistance and a number of other properties from the 



40 Sewall. Cited from Calmette. 



