PAPERS ON MEDICINE AND PUBLIC HEALTH 467 



high degi'ee of lasting immuuity. It was in this paper 

 that he made that memorable suggestion that human kind 

 might thus be actively immmiized by neutral mixtures of 

 toxin and antitoxin. 



This idea was so revolutionary and contrary to accept- 

 ed theories that it attracted no attention. Two years 

 later, in 1909, this medical Leverrier, with the courage 

 of his convictions, again pointed the way to human im- 

 munization. Three years more followed and still no one 

 arose to follow Smith's prophetic linger. It was not un- 

 til 1912 and 1913 that Behring himself, who had evidenth 

 experienced a change of heart, without mentioning 

 Smith's name, reported successful active immunization 

 with TA mixtures. The fear of the known effects of 

 diphtheria toxin on the nerves and heart, together vdtla. 

 Behring 's dictum mentioned before in this paper, mi- 

 doubtedly deterred research workers and clinicians from 

 the earlier use of TA mixtures. It seems to me no one 

 can read Smith's reports and not be convinced that TA 

 mixtures do produce a lasting immunity in these animals. 



Experimentation has abundantly proved that the tests, 

 manifestations of the disease, immunity and susceptibil- 

 ity observed in the guinea pig are exactly the same in 

 human kind. TA mixture, as the name indicates, is a 

 simple mixture of the diphtheria toxin with antitoxin in 

 which the toxin is not quite neutralized. It is given sub- 

 cutanously in three doses of 1 cc. each at intervals of 

 seven days. Immunity develops slowly, often not reach- 

 ing its maximum until five or six months have elapsed. 

 Experience shows that about ninety percent of the chil- 

 dren receiving the three doses have been rendered im- 

 mune during the whole period of observation, namely 

 three to seven years. You vnll hear undoubtedly of the 

 danger of giving these TA mixtures. In fact several 

 deaths resulted in Dallas, Tex., because a mistake was 

 made in the laboratory in the preparation of the mix- 

 ture, I have given about 3500 injections in children 

 without an unpleasant result. Park and Zingher in Xew 

 York have given thousands and thousands of these in- 

 jections without a death or loss of an arm. I had one 



