76 RALPH S. LILLIE. 



properties which are directly determined by the specific proper- 

 ties of the foreign protein introduced. The intimate relationship 

 between the phenomena of immunity and the phenomena of 

 normal assimilation has been pointed out by Ehrlich and others. 

 And since heredity is primarily a matter of assimilation i. e., 

 construction of the like it seems clear that the construction of 

 specific protein in the normal processes of growth is the expres- 

 sion of a similar determination of specific constructive processes 

 in the cell by means of the proteins normally present. In other 

 words, the structural proteins already present must determine the 

 production of similar proteins. 



The above tendency of structurally similar compounds to form 

 aggregates when they separate from solution is probably the 

 essential reason why the proteins native to the cell already 

 forming part of its structure undergo increase in quantity, with 

 the result that the cell grows. Nothing less than this is to be 

 inferred from the fact that proteins form the basis of specific 

 structures, and that the preservation of the normal characters 

 of any living cell depends upon the continual formation and refor- 

 mation of these particular compounds. Those proteins which 

 are already laid down as structure within the living cell are thus 

 to be regarded as acting as centres of deposition of further pro- 

 tein identical in composition and configuration. It seems neces- 

 sary also to conclude that these same structural proteins directly 

 control or guide the actual synthetic process by which more pro- 

 tein of the same kind is built up, presumably by the dehydrolytic 

 condensation of the amino-acids present in the protoplasm. 

 The precise and specific mode of union corresponding to any par- 

 ticular structural protein would then be determined by the specific 

 character of the protein itself. Such a conception would corres- 

 pond to that of specific catalyzers the usual manner of conceiv- 

 ing these phenomena at present the only difference being that 

 the structural protein would itself play the part of catalyzer. 

 Such a process would constitute a form of autocatalysis; the re- 

 semblance of growth to an autocatalytic process has in fact been 

 emphasized by Loeb, Robertson, and others. 1 The structural 



1 Cf. J. Loeb, Biochem. Zeitschr., 1906, Vol. 2, p. 41. T. B. Robertson, Arch. f. 

 Entwicklungsmech., 1908, Vol. 25, p. 581. Wfg. Ostwald: Roux's Vortrage und 



