226 PASSIVE IMMUNIZATION 



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 c.c. rather than in antitoxin units. 



Von Behring's fluid antitoxin is marketed in 100 unit (10 c.c.) 

 and 20 unit (2 c.c.) doses; in addition to this a solid antitoxin, of 

 which 20 units represent a dose is also available. 



Dosage and Uses. For prophylactic purposes, 20 units (2 c.c.) 

 should be injected about the site of injury, and if large nerve trunks 

 have been exposed, in part into their substance; the idea being to 

 bind the toxin which is formed about the point of infection, before 

 it leaves this district, which takes place along the lymphatics and 

 the nerve fibers. At the same time, it is recommended to give 

 a subcutaneous injection of 100 additional units (10 c.c.) at an 



