IMMUNITY AND ADAPTATION. I 5 I 



of the tissue coagulins. It might be of interest to examine the 

 existence of such a substance in leeches which had never had an 

 opportunity of sucking blood containing an active thrombin, e.g., 

 of leeches which had been nourished on blood which had been 

 previously heated to 56, and to investigate whether the desert 

 animals raised at places where they are exempt from scorpion 

 bites, would nevertheless develop immunity against scorpion 

 bites. 



If a hereditary fixation of the production of an antibody 

 should take place, then such a substance could be formed inde- 

 pendently of the presence of the substance which originally 

 caused its production and the origin of such an adaptation would, 

 if regarded as an isolated fact, not be apparent. 



In connecting these different facts it was intended to show the 

 analogy existing between several adaptations which are probably 

 fixed by heredity and certain reactions of the animal organism 

 which can be produced experimentally. If we shall be able to 

 clear up more and more the phenomena of experimental immu- 

 nization \\& may hope to explain by the same studies, one factor 

 which seems to form an essential part of many adaptations. 



Most of the reactions considered so far are useful for the 

 organism in which the reaction is taking place. It is, however, 

 possible to produce experimentally reactions of a similar char- 

 acter, in which no useful result can be recognized. It is further- 

 more not unlikely that the same principle (the formation of anti- 

 bodies) may under certain naturally occurring circumstances lead 

 to conditions which are injurious to the animal organism, as in 

 the case of destructive processes taking place in one kidney. 

 Uremia is explained by Ascoli through the formation of nephro- 

 lysins. It has been thought possible to explain on a similar 

 basis through the formation of syncytiolysins conditions of such 

 an acute pathological character as eclampsia. How far these 

 views are correct, it is at present impossible to determine. The 

 possibility must, however, be conceded that the same principle 

 underlies equally very striking adaptations and somewhat less 

 apparent disease producing processes. In recognizing this it will 

 be easier to apply to the phenomena of adaptation the same 

 causative investigation as to other phenomena. 



