IMMUNITY 75 



SERUM AND VACCINE THERAPY 



The principles underlying the production of diphtheria 

 antitoxin have already been described. Injected into a 

 patient suffering from diphtheria, the antitoxin at once 

 lays hold of the toxin which the diphtheria bacilli are 

 producing and quickly restores the patient to health. 

 The great convenience in the use of diphtheria antitoxin 

 lies in the fact that we can get a horse to produce it for 

 us, and then by bleeding the animal, collecting the se- 

 rum, and injecting this serum into man, can confer im- 

 munity against diphtheria on the person so injected. We 

 speak of this kind of immunity as passive immunity, 

 because the man's body has taken no active part in the 

 production of the protective substance, the antitoxin. 

 It is, of course, plain that the antitoxin can merely ward 

 off from the cells of the body the toxin which is threaten- 

 ing them; the toxin which has already begun to act on 

 the cells cannot be neutralized by the antitoxin. In 

 every case of diphtheria, therefore, it is most important 

 to give the full dose of antitoxin as early as possible, and 

 to give a small dose also to all who have been or expect 

 to be in direct contact with the patient. 



In the case of tetanus antitoxin the clinical results 

 have not been as striking as with diphtheria antitoxin. 

 Its use in the form of preventive injections has undoubtedly 

 saved many lives. Moreover, if injected intraspinally, 

 tetanus antitoxin is very useful in the treatment of tetanus. 

 In the past, when the serum was administered intra- 

 venously, the therapeutic results were very poor. One 

 reason why the serum often fails in the treatment of 

 developed cases of tetanus is because the diagnosis 



