572 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



not indicate, however, wherein the individuality differentials of different indi- 

 viduals differ from each other. In a similar manner we have seen that the 

 introduction of new sidechains or haptens into a protein may change or 

 destroy the species differentials ; but it would not necessarily follow that 

 actually the various species differentials represent combinations of proteins 

 with different sidechains or haptens; on the contrary, it seems certain that 

 as far as haptens are concerned pure proteins may be representative of species 

 differentials. Still, our knowledge as to the chemical properties of proteins, 

 on which these species differentials depend, is extremely fragmentary. It is 

 the tissue and serological reactions which have given us our first basic and, 

 so far, the only definite data regarding the organismal differentials. How- 

 ever, some of the chemical-physical differences which have been established 

 between the proteins of different species may be suggestive in this connection ; 

 no positive data of this kind exist regarding individuality differentials. As 

 mentioned, in the beginning of this chapter, more recent investigations, espe- 

 cially those of Svedberg, indicate that the native cell and tissue proteins are 

 more complex and represent longer peptid chains than had been assumed. 

 In particular, concerning the hemocyanins, Svedberg has shown that the 

 molecular weights of these substances, as they are present in the blood of 

 certain species, are always simple multiples of the well defined component with 

 the lowest molecular weight. These components are interconnected by reversible 

 dissociation-association reactions, which are influenced by the pH. The range 

 of pH in which these complex hemocyanin molecules are stable is characteristic 

 of the hemocyanins of different species. But marked differences in the pH 

 stability diagram occur only for species belonging to different orders. All the 

 species of the same order have similar diagrams. In addition to this pH range, 

 the isoelectric point of the hemocyanins of different species is to some extent 

 characteristic of the species. 



In regard to the hemoglobins, the extensive investigations of Reichert and 

 Brown to which we have already referred, have shown that their crystal form 

 differs in different species ; likewise, the readiness with which they crystallize 

 differs. But there is the possibility that in these determinations other proteins 

 from cells may have been admixed to the hemoglobin crystals and may have 

 contributed to the differences between the crystals of different species. As to 

 the chemical constitution of hemoglobins, it seems that the hemoglobins of 

 horse, sheep, cattle and dog contain the same amount of the basic amino-acids, 

 arginin, histidin and lysin, but differ in their cystin content and in the amount 

 of total sulfur (Block and Vickery). Horse and donkey hemoglobin differ 

 also in their solubility, although they cannot be distinguished by the precipitin 

 test (Landsteiner and Heidelberger). Bailey has found that in myosin the 

 amid nitrogen, expressed in percentage of total nitrogen, is about the same 

 in mammals, birds, fish and lobster; and the same applies as far as the 

 percentage composition of cystin, methionin, tyrosin and tryptophan is con- 

 cerned. On the other hand, the differences between the amino-acids which 

 occur in myogen and myosin within the same species are very considerable, 



