774 PASSIVE IMMUNIZATION SERUM THERAPY 



other molecules of antitoxin; this is one reason for the necessity of giv- 

 ing large doses of antitoxin in order than an excess may be at hand. 



2. When tetanus toxin has once united with nerve-cells, it is difficult 

 or impossible for the antitoxin to effect its neutralization. Hence the 

 greatest value of the antitoxin lies in prophylaxis; when properly ad- 

 ministered, however, it is possible for the antitoxin to aid in the cure of 

 tetanus, and its use should never be omitted in the treatment of any 

 case. 



The value of antitoxin in the treatment of tetanus is probably de- 

 pendent upon the following two factors: (1) Neutralization of all free 

 toxin as quickly as it is secreted and before it is absorbed by the nervous 

 tissue; (2) actual dissociation or neutralization of some of the toxin 

 "loosely united" with nerve-cells or suspended in the lymph after it 

 has left the capillaries and before it is taken up by the nerve-cells. 



3. Aside from its chief antitoxic action, anti- tetanus serum probably 

 contains anti-aggressins or bacteriotropins that aid phagocytosis by 

 overcoming their repelling or negatively chemotactic influence. This 

 may, however, be accomplished by simple neutralization of the toxins, 

 which impairs their leukotoxic action sufficiently to permit living leuko- 

 cytes to engulf and destroy the bacilli. 



Methods of Administering Tetanus Antitoxin. Recent investiga- 

 tions and case reports show quite conclusively that in the treatment of 

 tetanus as much depends upon the method of administering antitoxin 

 as upon the quantity administered. 



1. Absorption by the subcutaneous route is so slow that it should not be 

 depended upon in the treatment of tetanus. While it is true that the mor- 

 tality of tetanus has been reduced about 20 per cent, by the administra- 

 tion of large amounts of serum by this route, it should be emphasized 

 that a smaller amount, given subdurally or intravenously, will yield even 

 better results. Knorr has shown experimentally that after subcutaneous 

 injection the maximum quantity of antitoxin is not found in the blood 

 until twenty-four hours have elapsed. Since every hour counts heavily 

 in the chances for recovery when symptoms of tetanus have appeared, 

 it may be laid down as a general rule that the first doses of antitoxin 

 should be given subdurally or intravenously. The subcutaneous route 

 may be chosen when serum is given for prophylactic purposes at the time 

 of injury, but should not be relied upon in the treatment of tetanus. 



2. Intramuscular injections may be given to keep up the good effect 

 of antitoxin after the first doses have been given subdurally and intra- 

 venously, and are to be preferred to the subcutaneous route whenever 

 the physician is unable to inject the serum subdurally and intravenously. 



