204 SCIENCE PROGRESS. 



guinea pigs of the same weight which have undergone 

 previous inoculations of small doses of toxin from which 

 they have perfectly recovered causes death (34). Several 

 deductions may be drawn from these experiments, but most 

 probably the results are dependent upon an artificial weaken- 

 ing of the organism in the latter case. Upon the bacilli of 

 diphtheria, antitoxic serum exerts no destructive power ; 

 the bacilli may even grow more vigorously upon the serum of 

 immunised animals than upon that of normal individuals (35). 

 The views originally held by Behring — that "passive 

 immunity/' a term first employed by Ehrlich, which can be 

 established by the injection of the blood-serum of an im- 

 munised animal, is a simple transport of something which 

 has caused the immune condition — have undergone but 

 little change since the date of his original discovery in 

 1890(36). In his most recent paper (37) he maintains that 

 specific antitoxins have only been found in the blood of im- 

 munised animals. An organism which is perfectly healthy 

 is absolutely unaffected by injection of antitoxic serum ; it 

 is only a diphtheria-stricken organism which responds to 

 the injection. The antitoxin of diphtheria is protective 

 and curative only for this specific malady, and other 

 diseases which have been treated by antitoxic serum are 

 only benefited when the serum employed has been obtained 

 from animals rendered artificially immune to the particular 

 disease which it is desired to heal. The antitoxin which 

 exists in the body arises by the action of the toxin on 

 certain proteids of the organism. The fever and general 

 constitutional disturbances which supervene on injection of 

 toxin indicates that the organism attempts to actively de- 

 fend itself against the entry of the poison. As the result 

 of this antitoxins become developed, and in such an amount 

 that not only may the toxin be rendered inert and harm- 

 less, but the excess may be utilised by transference to 

 another animal. Curative effects can also at times be 

 obtained by the introduction of toxins which have been 

 weakened in virulence by chemical or physical agents, 

 instead of antitoxic serum. This is an especially valuable 

 treatment, not for an acute diphtheria, but for the paralytic 



