PRESENT PROBLEMS 349 



the bactericidal action of blood-sera, the effect of oxidizing enzymes, 

 of animal and vegetable origin, upon toxins of various kinds, etc. 

 Ehrlich's theories regarding the protection furnished by antitoxic 

 and bactericidal sera, so elaborately devised, constitute a working 

 hypothesis of great value, but we need much additional knowledge 

 concerning the nature and action of the so-called complements and 

 anticomplements, of amboceptors, of haptophor groups, of agglu- 

 tinins, of precipitins, and of hemolysis. The physiological chemist 

 studies with care the important and suggestive work being carried 

 forward by the many brilliant investigators in pathology and bacteri- 

 ology, with the feeling, however, that the true explanations for most 

 of the phenomena in question are chemical, and that the actions and 

 interactions involved are chemical ones, to be eventually made clear 

 by a fuller chemical knowledge of the toxic and antitoxic substances 

 themselves and of their alteration and combination under different 

 physiological conditions. 



The well-known natural immunity possessed by some animals 

 toward certain diseases, together with the difficulty experienced by 

 most micro-organisms in developing in the healthy body, a difficulty 

 which at once disappears when from any cause the tissues of the body 

 lose their original vitality and vigor, all point to the presence in the 

 healthy body of certain general or specific substances which are directly 

 deleterious to the micro-organisms. Such substances are obviously 

 bactericidal, and it is equally plain that in the bodies of many species 

 of animals there are specific antisubstances present which are lacking in 

 other species, thereby explaining the natural immunity of the former 

 towards certain diseases. As is well known, blood-serum possesses, as 

 a rule, a bactericidal power upon most micro-organisms, and we have 

 every reason to believe in the existence of specific substances in the 

 serum which exert some influence upon the growth and development 

 of micro-organisms, and also upon the toxic products they tend to 

 elaborate. These protective substances the alexins of Buchner 

 appear to be proteid in nature, resembling globulins, since they are 

 precipitated from serum by the action of certain strong solutions of 

 alkali salts, as sodium sulphate. We know, however, very little re- 

 garding their chemical nature aside from the fact that they are ob- 

 viously very complex, although perhaps even this point is not quite 

 certain. These protective substances are presumably elaborated by 

 the leucocytes of the blood and lymph, cells rich in nuclein andnucleo- 

 proteid material. Doubtless, also, some of the gland-cells in the body 

 have a corresponding action; statements which, if true, tend to 

 emphasize the possible proteid nature of the protective substances. 



While in a general way we may say that the natural immunity to 

 certain bacteria possessed by some animals is due in large measure to 

 an inhibition of the growth of the micro-organism, it must also be 



