114 BACTERIOLOGY. 



tected from access of air, the more resistant antitoxins 

 may be preserved sometimes for a year or two with 

 practically no deterioration in strength. At other 

 times, however, from unknown causes, they are gradu- 

 ally destroyed, so that there may be a loss of about 10 

 per cent, per month. A serum requires, therefore, to be 

 tested every few months if we wish to be assured of its 

 strength in antitoxin. Preservatives, such as carbolic 

 acid, trikresol, camphor, etc., alter antitoxins only very 

 slightly when in dilute solution, but in strong solution 

 they partially destroy them. Heat up to 62 C. does 

 not injure them greatly, but higher temperatures alter 

 them. In animals injected with diphtheria toxin 

 Atkinson has found that there is with the increase in 

 antitoxin an almost proportional increase in globulin. 1 

 He also found that the antitoxins behave like globulins 

 with the various reagents, being completely precipi- 

 tated by magnesium sulphate. NaCl, when added to 

 saturation to globulin solutions holding antitoxin, parti- 

 ally precipitates the globulin and the antitoxin. When 

 raised to 72 C. a series of precipitations are obtained 

 which contain at least the greater part of the antitoxin. 

 Whether this indicates that antitoxin is a form of 

 globulin or merely that it is similarly affected by many 

 reagents, and that the toxin in some way stimulates the 

 development of both, it is as yet impossible to say. 

 Although in a very rough way, the same animal pro- 

 duces antitoxin in direct proportion to the amount of 

 toxin injected so long as its condition remains good, yet 

 different animals of the same species give very varying 

 amounts from the same injections, some not giving one- 



1 This work, carried out in the Research Laboratory of the Department of 

 Health of New York City, will appear in the Journ. of Exp. Med. in 1900. 



