PREFACE. 



The present memoir, which is purely in the nature of a report of a preHminary 

 investigation, is complementary and supplementary to Publication No. 116 of 

 this Institution, entitled "The Differentiation and Specificity of Corresponding Pro- 

 teins and other Vital Substances in Relation to Biological Classification and Organic 

 Evolution: The Crystallography of Hemoglobins," in the preface of which the 

 following statement was made of the hypothesis upon which the research was 

 founded, and of the support of the hypothesis by the results of the inquiry: 



"The trend of modern biological science seems to be irresistibly toward the explana- 

 tion of all vital phenomena on a physico-chemical basis, and this movement has already 

 brought about the development of a physico-chemical physiologj', a physico-chemical 

 pathology, and a physico-chemical therapeutics. The striking parallehsms that have been 

 shown to exist in the properties and reactions of colloidal and crystalloidal matter in vitro 

 and in the living organism lead to the assumption that protoplasm may be looked upon as 

 consisting essentially of an extremely complex solution of interacting and interdependent 

 colloids and crystalloids, and therefore that the phenomena of life are manifestations of 

 colloidal and crystalloidal interactions in a peculiarly organized solution. We imagine 

 this solution to consist mainly of proteins with various organic and inorganic substances. 

 The constant presence of protein, fat, carbohydrate, and inorganic salts, together with the 

 existence of protein-fat, protein-carbohydrate, and protein-inorganic salt combinations 

 justifies the belief that not only such substances, but also such combinations, are absolutely 

 essential to the existence of life. 



"The very important fact that the physical, nutritive, or toxic properties of given 

 substances may be greatly altered by a very slight change in the arrangement of the atoms 

 or groups of molecules may be assumed to be conclusive evidence that a trifling modifi- 

 cation in the chemical constitution of a ^'ital substance may give rise to even a profound 

 alteration in its physiological properties. This, coupled with the fact that differences in 

 centesimal composition have proved very inadequate to explain the differences in the 

 phenomena of living matter, implies that a much greater degree of importance is to be 

 attached to peculiarities of chemical constitution than is universally recognized. 



"The possibilities of an inconceivable number of constitutional differences in any 

 given protein are instanced in the fact that the serum albumin molecule may, as has been 

 estimated, have as many as 1,000 million stereoisomers. If we assume that serum globulin, 

 myoalbumin, and other of the highest proteins may have a similar nimiber, and that the 

 simpler proteins and the fats and carbohydrate, and perhaps other complex organic sub- 

 stances, may each have only a fraction of this number, it can readily be conceived how, 

 primarily by differences in chemical constitution of vital substances, and secondarily by 

 differences in chemical composition there might be brought about all of those differences 

 which serve to characterize genera, species, and individuals. Furthermore, since the 

 factors which gi\-e rise to constitutional changes in one vital substance would probably 

 operate at the same time to cause related changes in certain others, the alterations in one 

 may logically be assumed to serve as a common index of all. 



