THE BACILLUS AND THE BACTERIOLOGY OF DIPHTHERIA 207 



From this, as needed, small phials are filled. The phials and their 

 stoppers, as indeed all the utensils used for holding the serum, must be 

 absolutely sterile, and every possible precaution must be taken to avoid 

 contamination of the serum. An antiseptic may be added to the serum 

 as a preservative, but it is not necessary except when the serum is to 

 be sent to great distances, where it cannot be kept under supervision. 



Kept from access of air and light and in a cold place it is fairly stable, 

 deteriorating not more than 40 per cent., and often much less', within 

 a year. Diphtheria antitoxin, when stored in phials and kept under 

 the above conditions, contains within 10 per cent, of its original strength 

 for at least two months; after that it can be used by allowing for a 

 maximum deterioration of 5 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. Almost all producers put more units in the phials than the 

 label calls for so as to allow for the gradual loss of strength. 



The nature of diphtheria antitoxin has until recently been known 

 almost wholly from its physiological properties. Experiments have 

 seemed to show that it was either closely bound to the serum globulins 

 or was itself a substance of proteid nature closely allied to serum 

 globulin. Mr. J. P. Atkinson, when assistant chemist in the laboratory, 

 found that antitoxic and normal horse serum react similarly toward 

 MgSO 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 diphtheria 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 precipitation occurs at 45, 54, 

 62, and 72 C. Each of these precipitates has antitoxic properties, 

 and the total quantities contain all the original antitoxin except ome 

 5 per cent., which is evidently 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 the antitoxin strength increases. 

 It seems, therefore, from the above that diphtheria antitoxin has the 

 characteristics of the serum globulins. Antitoxin is destroyed by pro- 

 longed moderate heat (60 C.) and by short exposure to higher tem- 

 peratures (95 to 100 C.). It is less sensitive than diphtheria toxin. 



Diphtheria antitoxin has the power of neutralizing diphtheria toxin, 

 so that when a certain amount is injected into an animal before or 

 together with the toxin it overcomes its poisonous action. The facts 

 in favor of a direct action of antitoxins upon their corresponding toxins 

 have recently been briefly summarized by Cobbett as follows: 



1. Certain reactions j^ave been observed to take place between these 

 substances outside the animal body* (venom, ricin, crotin, tetanus toxin, 

 diphtheria toxin, and their corresponding antitoxins). 



