230 PASSIVE IMMUNIZATION 



gave 4000 to 5000 units every five days for four weeks, in severe 

 cases. At the Berlin Charite four-fifths of the cases require from 

 1500 to 4500 units; in the remainder 9000 to 18,000 are common 

 amounts, and in the severest cases 30,000 to 65,000 have been used. 

 Above all, then, the physician should not despair in the face of a 

 grave case, but use the antitoxin systematically until the child is 

 either dead or out of danger. The same rule applies in the man- 

 agement of those cases in which post-diphtheritic paralyses have 

 occurred. In the past it was thought that antitoxin would be of 

 no avail in such cases, but in the light of more recent experience it 

 would seem that here also much good may come from the systematic 

 use of the serum. 



The question, of course, suggests itself, why antitoxin should still 

 be of service when once the toxin has been anchored to sensitive 

 receptors; but I would recall that as a consequence of immunization, 

 the specificity of the receptors for the corresponding antigen may be 

 very materially increased and that the toxin in question will hence 

 have a greater affinity for the antitoxin furnished by the horse 

 than for the sessile receptors of the patient. Hence, the possibility 

 exists, theoretically at least, that an active antitoxin may be able to 

 break the combination between the toxin and the patient's recep- 

 tors, and our clinical experience suggests that this actually occurs. 

 To effect this end, however, large doses are evidently necessary. 



Prophylactic Dose. For prophylactic purposes a dose of from 

 500 to 1000 units has been found sufficient to afford protection for 

 approximately three weeks (see curve above). Whether or not 

 this period could be lengthened by the administration of larger 

 amounts seems doubtful, in view of the fact that the drop in the 

 blood content of antitoxin which takes place within the first few 

 days of its injection is the more abrupt the larger the dose. This 

 will be understood if we bear in mind that the antitoxic properties of 

 horse serum are intimately connected with its globulins, and that 

 these are alien albumins which the body cannot utilize as such and 

 which it accordingly tries to destroy as soon as possible. 



Centra-indications to the Use of Antitoxin. In view of the fact that 

 a small number of people are hypersensitive to the use of horse serum 

 to such a degree that a first injection even may be followed by most 

 alarming symptoms, and in rare instances by death, some physicians 

 have of late hesitated to use antitoxin as promptly as has generally 



