676 LECTURE XXIX. 



in such a way that the egg-cell, as a part of the mother's organism, is 

 affected by the disturbance, still this will not hold for the transmission of 

 many other properties. In this direction we have the peculiarity in the 

 inheritance of hemophilia, as we have already indicated. 



If we consider the cells in their entire chemical construction, and con- 

 stantly bear in mind that herein lies their entire function, we can indeed 

 imagine that a faulty organization of the cell will have an influence upon 

 the general metabolism. The conception of the disposition which plays 

 such an important part in pathology is certainly well founded, and the 

 cause of it is to be sought in the state of the function of certain groups of 

 cells, or the whole cell state of the body may be affected in such a way that 

 the individual appears to be functionally deficient. Naturally such spec- 

 ulations, which have no experimental justification, do not penetrate at all 

 into the nature of a disposition; but, nevertheless, it seems fitting to sug- 

 gest that an alteration in the chemical processes of the cells themselves 

 may come into consideration here. 



Let us now turn back to the limitations of the concept of species on 

 a basis of physiological-chemical investigation. We have mentioned only 

 a few of the species which have been most thoroughly studied. We might 

 multiply these examples, but a few suggestions should prove sufficient. 

 We know that the general metabolism of different animals is unlike. 

 This is partly due to the different kinds of nourishment which they receive. 

 Thus we can readily understand that the urine of herbivora will be of 

 quite different composition from that of pure carnivora, and that of 

 the latter will likewise be different from that of omnivora. We even 

 find differences in the same animal species. We recall in particular the 

 amount of kynurenic acid present in the urine of dogs. We encounter 

 other characteristics which indicate that each species of animal has a 

 peculiar cell-metabolism. We do not doubt at all that there are also 

 individual differences. The fact that there is a perfectly definite endogenic 

 uric acid value for each individual points in this direction. Also the pecul- 

 iar characteristic color of the skin, hair, eyes, etc., gives one the impression 

 that it is the expression of a specialized individual metabolism of certain 

 definite cell-complexes. Each individual possesses its own characteristic 

 smell. This is usually not observed by human beings, but that there are 

 such distinctions is evident from the ability of certain animals, such as the 

 dog, to trace a person by the scent. 



The differentiation of the species increases infinitely in the case of lower 

 animals, especially the anthropods. What a richness of coloring, and what 

 splendor in the groups of butterflies and beetles! Each separate color is an 

 expression of the chemism of the cells producing it. We meet with the 

 same phenomena in the plant world, where the beautifully colored flowers 

 indicate an unsuspected variety of peculiarly modified chemical processes. 



