234 PASSIVE IMMUNIZATION 



disease. As a matter of fact there are physicians who have not a 

 single death to record among just such cases, even though their 

 experience is based upon a fairly large number of observations. 

 Nevertheless, there are instances where the injections have been 

 started in time and in which death nevertheless occurred (see table 

 above). Whether any of these could have been saved by injecting 

 the antitoxin intravenously or by using larger doses is now, of course, 

 impossible to say, but the possibility unquestionably exists. But 

 even so we should remember that our serum is after all purely anti- 

 toxic in character, and that unless the body can successfully destroy 

 the infecting organisms the battle may yet be lost, and it is this 

 factor which may be responsible for the number of deaths that yet 

 occur, even though the antitoxin be used at the very start. To 

 overcome this possible obstacle to a zero mortality it would be 

 tempting to use a corresponding vaccine simultaneously with the 

 antitoxin. This has indeed been advocated by several investigators 

 and deserves serious consideration. Petruschky records that he 

 has succeeded in freeing bacillus carriers in this way of their 

 dangerous guests. 



TETANUS 



The preparation and titration of tetanus antitoxin is based upon 

 practically the same principles as that of diphtheria antitoxin, which 

 we have considered in some detail in the foregoing section. The 

 standards employed in Germany are the following: 



One unit of toxin is that quantity which is capable of killing 

 4,000,000 white mice (of an average weight of 10 grams each) within 

 four or five days with the characteristic symptoms of tetanus. 



A toxin solution of such strength that 1 c.c. contains one unit of 

 toxin is designated as normal toxin. 



One unit of antitoxin is that quantity which will protect a mouse 

 weighing 10 grams against 4,000,000 fatal doses of toxin, when 

 injected subcutaneously. 



A normal antitoxic serum is one of which 1 c.c. contains one unit 

 of antitoxin. 



In the United States an official standard unfortunately does not 

 yet exist, and as the standards of the different manufacturers are 

 not alike, physicians are practically obliged to express their dosage 

 in terms of cubic centimeters rather than in antitoxin units. 



