230 RALPH S. LILLIE AND EARL N. JOHNSTON. 



trates. In the chief compounds forming the structural basis of 

 living protoplasm, the proteins, we have molecules of great 

 complexity, consisting essentially of chains of asymmetric 

 molecules united by an easily dissoluble linkage; it is this struc- 

 ture which renders possible the high degree of specificity shown 

 by the individual proteins. There is definite evidence that to 

 this chemical specificity corresponds an equally definite mor- 

 phological or structural specificity in the crystalline or other 

 aggregates formed by proteins when they separate out from 

 solution. Reichert and Brown's observations indicate that if 

 our knowledge were sufficiently exact and detailed different 

 species could be distinguished and identified by the crystal-forms 

 of their haemoglobins,' just as birds can be distinguished by their 

 feathers; and presumably similar relations between specific 

 molecular structure and the structure of solid aggregates hold 

 true for homologous proteins of other kinds. Probably it is to 

 the intimately or microscopically crystalline nature of the de- 

 posits that the possibility of distinguishing different protein 

 precipitates by their microscopic characters is due. 2 According 



1 Cf. Reichert's very suggestive article, "the Germ-plasm as a Stereochemic 

 System," Science, 1914, N.S., Vol. 40, p. 649. Reichert also regards heredity as 

 ultimately an expression of the influence of the specific structural characters of the 

 cell-proteins upon the course of formative metabolism. "Given as the basis of 

 scientific study a germ-plasm that has inherently the power of development; that 

 is in the form of a Stereochemic system that is peculiar to the organism; that is 

 highly impressionable to stimuli; and that has the marked plasticity that is inherent 

 to organic colloidal matter, we have all the postulates that are needed as a founda- 

 tion upon which, according to the laws of physical chemistry, can be built a logical 

 explanation of the essential fundamental elements of the mechanism of heredity . . . 

 The typical condition of matter of definite composition is crystalline. . . . Having 

 a homogeneous solution of various selected crystalline substances of appropriate 

 chemical composition and constitution, and given conditions attendant to crystal- 

 lization, the successive stages of crystalline development will proceed along fixed 

 and definitely recognized lines. . . . Having in the germ-plasm an analogous 

 physico-chemical system, . . . the phenomena of development likewise proceed 

 in conformity with the same laws along definite lines ..." (pp. 656-7). These 

 quotations will indicate Reichert's general point of view. His conception of the 

 manner in which this specific structure influences metabolism and thus determines 

 further structure-formation is, however, different from that outlined in the present 

 paper. 



- This seems possible to a considerable degree. Alfred Fischer's work, "Fixier- 

 ung, Farbung und Bau des Protoplasmas," Jena, 1899, Chapters 3-5, represents 

 a beginning in this direction; further development of this technique seems desirable. 



