362 BACTEEIOLOOY. 



original strength for at least two months; after that it 

 can be used by allowing for a maximum deterioration 

 of 10 per cent, for each month. The antitoxin in old 

 serum is just the same as in that freshly-bottled, only 

 there is less of it. 



The nature of diphtheria antitoxin has until recently 

 been known almost wholly from its physiological prop- 

 erties. Recently experiments have seemed to show that 

 it was either closely bound to the globulins or was itself 

 a globulin. Mr. J. P. Atkinson, assistant chemist in 

 the laboratory, has kindly permitted me to state the 

 results of his investigations, which will soon appear in 

 the Journal of Experimental Medicine. He found that 

 antitoxic and normal horse-serum react similarly toward 

 M'gSO 4 , in that the globulin is precipitated completely 

 from the other constituents of the serum. In the case 

 of antitoxic serum the globulin precipitate carries with 

 it all of the antitoxic power of the serum, leaving the 

 filtrate without any neutralizing power against the diph- 

 theria toxin. When watery solutions of this globulin 

 are saturated with NaCl a precipitate occurs. When 

 the solution is heated a series of further precipitates take 

 place, as follows : Cloudiness appears at 40, 49, 57, 

 and 67 C. ; complete precipitate occurs at 45, 54, 

 62, and 72 C. Each of these precipitates has anti- 

 toxic properties, and the total quantities contain all the 

 original antitoxin except some 5 per cent., which is evi- 

 dently destroyed by the higher temperatures required 

 for the last two precipitates. After the last precipitate 

 the solution is free of globulin and also of all antitoxic 

 properties. 



A further fact developed by Atkinson is that the 

 globulins increase markedly in the serum of horses as 



