200 Immunity in So ine of iis Biochemical As pect s [Jan. 



therefore also Organotropie. In the employment of chemical sub- 

 stances to combat infectious diseases, it follows that success can only 

 be attained if the affinity of the chemical substances for the infecting 

 parasite bears certain relations to their affinity for the infected body. 

 Ehrlich's studies in this direction have, therefore, aimed to find 

 poisonous substances whose parasitotropic affinity should be great 

 in comparison to their Organotropie affinity. In his studies on Syph- 

 ilis, he tested a very large number of substances, many of them com- 

 binations of arsenic. As each substance was tested it received a 

 serial laboratory number, and finally, in " 606," a substance was 

 found which fitted the requirements to a high degree. This sub- 

 stance, salvarsan, has produced really marvelous results in the treat- 

 ment of syphilis. This line of work appears very promising. 



Chemical natura of antibodies. A closing word concerning 

 the chemical nature of antibodies. Most of the studies have been 

 made on diphtheria antitoxin, and although little is known concern- 

 ing the Constitution of this substance, it seems proable that it is 

 protein in character. Certain it is that the antitoxin is associated 

 with the globulins of the serum, and highly concentrated Solutions 

 of antitoxin have been prepared, by Gibson, by precipitating and then 

 redissolving these globulins. Moreover, as Atkinson showed, the 

 globulins increase markedly in the serum of immunized horses as 

 the antitoxic strength of the serum increases. 



The influence which the development of the field of immunity 

 has had on biochemistry has been tremendous, for it has contributed 

 not only new view points, but also entirely novel methods. Much 

 has been learned about substances which no one had ever yet seen 

 and which we know only through their action. That all this has 

 been achieved is due mostly to one master mind, Paul Ehrlich. May 

 he long continue to lead us ! 



