474 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



action. There exist not only the first kinds of specificity, which imply that 

 one enzyme is different from another one and is peculiar to a certain species 

 or series of species and to a certain organ or tissue, but there has been 

 demonstrated, also, a specific adaptation in the sense here defined. Thus ac- 

 cording to E. N. Harvey, luciferin, the substance which, in being oxidized, 

 gives rise to luminescence, if acted on by the oxydation accelerating enzyme 

 luciferase, shows a specific adaptation to this enzyme. Only the enzymes 

 from the same species, or from species very closely related to the species 

 from which luciferin was obtained, seem to cause luminescence; if solutions 

 of luciferin and luciferase are prepared from Cypridina and Systellaspis, 

 the mixing of luciferin from one organism with the luciferase from the same 

 species leads to a marked production of light; but if the solutions of luciferin 

 from one species are mixed with the luciferase from the other species, the 

 results are negative. 



Another example from the field of enzyme activity is presented by certain 

 older observations of Hedin. There occurs in the gastric mucosa of various 

 vertebrates not only the milk-curdling enzyme rennet, but, according to Hedin, 

 also a substance inhibiting the enzymatic action of rennet, which can be 

 obtained if the enzyme is treated with NH 4 OH. This inhibiting agent is 

 specifically adapted to the enzyme of the same species, both of these sub- 

 stances, the enzyme as well as the inhibiting substance, carrying species dif- 

 ferentials. However, certain other substances, such as egg albumin and blood 

 serum, may also contain inhibiting substances for rennet, but they are non- 

 specific; charcoal, likewise, may act in a non-specific manner. The species 

 differential which is present in rennet participates in the antigenic function 

 of this substance and calls forth in the animal, immunized against the rennet, 

 the development of an anti-rennet, which is specifically adapted to rennet in 

 a way similar to the natural anti-rennet. However, these investigations may 

 perhaps have to be reconsidered in the light of more recent studies on 

 proteinolytic enzymes of the gastro-intestinal tract. As far as the various 

 enzymes and their precursors in the gastro-intestinal tract, which have been 

 separated in recent years by Northrop and Kunitz, are concerned, it has been 

 shown that their constitution differs in different species. Similarly, catalase 

 seems to differ somewhat in different species (Sumner); also the urease 

 which has been found in various tissues and in the blood serum of Limulus 

 seems to be specific for this animal (Loeb and Bodansky). However, no 

 instance of specific adaptation has been observed so far in these substances. 

 Considerably more readily demonstrable than the species-specificity is the 

 organ or "substance" specificity of these enzymes; each one is adapted to a 

 definite type of substratum. 



A specific adaptation is characteristic of many antigens and immune sub- 

 stances. In order to produce an antibody it is necessary to introduce into the 

 organism which is to be immunized, a substance sufficiently strange to it to 

 cause a certain disequilibrium. In many cases it is the introduction of a strange 

 organismal differential which serves as antigen and makes possible the pro- 

 duction of an antibody carrying the corresponding organismal differential. 



