XXXII. THE PROTECTIVE SUBSTANCES OF THE 



BLOOD. 1 



By Professor Dr. P. EHRLICH. 



MORE than ten years have passed since the studies of Fliigge 

 and of Buchner and of their pupils directed attention to the bac- 

 tericidal substances present in normal blood serum and their rela- 

 tion to natural immunity. Buchner especially assumed that the 

 serum of each animal species contained a simple definite protective 

 body, the alexin, which was able to kill off foreign cells, especially 

 bacteria and the blood-cells of other species; that this acts some- 

 what after the manner of a proteolytic ferment and leaves the cell 

 elements of its own species unscathed. The recent development 

 of the doctrine of immunity, inaugurated by v. Behring's discovery 

 of antitoxin, has also shed considerable light on the nature of pro- 

 tective bodies preformed normally, so that it now seems advisable 

 to subject the mutual relations existing between these to a closer 

 analysis. 



There can hardly be any doubt that, in accordance with the 

 principle enunciated by Virchow for the relation existing between 

 cell physiology and cell pathology > the normal protective substances 

 are subject to the same developmental laws as the artificially pro- 

 duced antitoxic and bactericidal substances. It is obvious that 

 with the artificially produced protective substances, especially with 

 the antitoxins, it will be far easier to gain an insight into the mechan- 

 ism of their development, for in this case one possesses not only 

 the exciting agent (as, for example, the toxin), but also the resulting 

 specific product (the specific antitoxin), making it possible to study 

 their mutual chemical relations. 



1 Address delivered in the general session of the 73d Congress of German 

 Naturalists and Physicians, Hamburg, Sept. 25, 1901. (Reprinted from the 

 Deutsche med. Wochenschrift 1901, Nos. 51 and 52.) 



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