ESSAYS ON BACTERIOLOGY. 93 



The chief theories in explanation of these facts are 

 two: first, that there is in the antitoxin serum a sub- 

 stance which directly antagonizes the growth of the 

 gemis or neutralizes the toxin, or both; second, that 

 its action is biological, rather than chemical, stimu- 

 lating the body to an increased resistance. There axe 

 strong arguments in favor of each view, but we ai'e 

 not yet in a position to decide the question. 



Meantime, the treatment has been applied in many 

 thousands of cases, and what of the results? Statis- 

 tics from many sources have been and are constantly 

 being published, and of their value and significance 

 others are as capable of judging as the writer. It 

 must be said that the weight of opinion is in favor of 

 the treatment. Certainly the majority of those who 

 have used it extensively believe it to have given re- 

 sults surpassing those of anything heretofore known. 

 Perhaps the-best summary of the whole matter is that 

 published by Welch, of Johns Hopkins University, 

 and widely quoted. His conclusions are that the anti- 

 toxin is of great value, is comparatively harmless, and 

 that it is our duty to use it. As a matter of record 

 the following extract from Dr. Welch's paper is here 

 given place: 



In Dr. Welch's contribution, an analysis of 7,166 

 cases of antitoxin-treated diphtheria is reported from 

 the hospitals of Germany, France, Austria and Amer- 

 ica. From a careful study of these cases, and from a 

 thorough sifting of all the evidence, the figures show 

 a mortality of IY.3 per cent. 



