THE CHEMICAL NATURE OF DIFFERENTIALS 573 



and much greater than the differences between the myosins of quite un- 

 related species. 



It is probable that not only the nature of the bonds between sidechains in 

 the same protein, but also the nature of the sidechains as such, may differ 

 in different proteins. Likewise, according to Bergmann, the various natural 

 proteins differ from each other in that their individual amino-acid constituents 

 are represented by different frequencies within the complex protein molecule. 

 This view implies that the physical-chemical and biological properties of a 

 particular protein depend in the last analysis on the frequencies with whix:h 

 the constituent amino-acid residues recur within its peptid chain. However, 

 no sharp distinction is made here between species-specific and organ- or 

 "substance"-specific proteins. Of great interest is the suggestion of Bergmann 

 that it is the cell enzymes, the proteinases (papainases) which not only split 

 the proteins, but also synthesize them from the constituent amino-acids of 

 the foodstuffs, and which, because they have a specific constitution, specifically 

 determine the specificity of the cell proteins which they build up ; therefore, 

 the cell enzymes and cell proteins must in each instance have the same 

 specific structural characteristics ; the process of constructing these proteins 

 would thus be autokatalytic. However, 'according to such a conception this 

 autokatalytic process should primarily lead to the new formation of specific 

 enzymes rather than of specific cell substratum. But it may be assumed that 

 secondarily these specific proteinases would also build up the cell proteins 

 in such a way that they possess the same characteristic species differentials 

 as the enzymes. This conception was applied to the species differentials of 

 cell proteins; but if it should be extended to the individuality differentials, 

 then it would be necessary to assume that also in the different tissues of the 

 same individual the proteinases not only possess the same species differential, 

 but also the same individuality differential, and these enzymes should then 

 differ in the reactions they call forth in different individuals in accordance 

 with the differences in their individuality differentials. However, such dis- 

 tinctions between the enzymes of different individuals have not yet been noted. 



By means of electrophoresis, Landsteiner could distinguish the egg 

 albumins of chicken, guinea hen and turkey from those of duck and goose, 

 but he could not establish definite differences within these two groups. It was 

 therefore possible to distinguish between the proteins of species belonging to 

 different orders, but not possible to distinguish between those belonging to 

 the same order, such as chicken, guinea hen, and turkey, or duck and goose, 

 though these could be distinguished by means of the precipitin reaction. This 

 lack of differences in the electrophoretic mobility of some of the egg 

 albumins obtained from different species of birds is in contrast to the dis- 

 covery, by Tiselius, of three different fractions differing in their electro- 

 phoretic behavior in the apparently homogeneous globulin of rabbit serum. 

 It is possible that in the protein molecules the organismal differential, 

 which may function also as antigen, is determined not by a small group, but 

 by larger groups ; this is suggested by the multiplicity of cross-reactions 



