PREFACE. 



memoir iii complementary and supplemen- 

 tary to publication N". \\<> of the Carnegie Insti- 

 tution of Washington, entitled " The Differentia- 

 tii-ii und SjHvilii-ity of Corresponding Proteins 

 and other Vital Substance* in relation to Biological 

 Classification and Organic Evolution: The Crystal- 

 lography of Hemoglobins," and publication No. 173 

 of the same series, entitled " Tin- Differentiation and 

 Specificity of Starches in relation of Genera, Species, 

 reochemiatry applied to Protoplasmic Proc- 

 eases and 1'nxliu-u, and aa a strictly scientific basis 

 for tli' Classification of Plants and Animals." Like 

 its predecessors, this is a report of an exploratory 

 -tigutiuii. In the preface of No. 173 there ap- 

 peared the following statement of the thoughts that 

 underlie these .-indies, and of their support up to that 

 time by the results of experimental inquiry: 



" I'll.- present memoir, which is purely in the nature 

 of a rcjMirt of a preliminary investigation, is comple- 

 mentary and supplementary to Publication No. 116 of 

 tin- h.-'itutitm. entitled 'The Differentiation and Spe- 

 cificity of Corresponding Proteins and other Vital Sub- 

 stances in Notation to Biological Classification and Or- 

 ganic Kvolution: 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 explanation of all vital phe- 

 nomena on a physico-chemical basis, and this movement 

 has already brought about the development of a physico- 



ical physiology, a physico-chemical pathology, and 

 a physico-chemical therapeutics. The striking parallel- 

 isms that have been shown to exist in the properties and 

 reactions of colloidal and crystalloid*] matter in ri/ro 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 in- 

 terdependent colloids and crystalloids, and therefore that 

 the phenomena of life are manifestation* of colloidal and 



illoidal interactions in a peculiarly organized solu- 

 tion. 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 com- 

 binations, justifies the belief that not only such sub- 

 stances, but also such combinations, are absolutely essen- 

 tial to the existence of life. 



The very important fact that the physical, nutri- 

 tive, or toxic properties of given substances may be 

 greatly altered by a very slight change in the arrange- 



ment 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 vital substance 

 may give rise to even a profound alteration in its physio- 

 logical properties. This, coupled with the fact that 

 <h (Terences in centesimal composition have proved very 

 inadequate to explain the differences in (hi phenomena 

 of living matter, implies that a much greater degr 

 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 at 

 stanced in the fact that the serum albumin m< 

 may, as has been estimated, have as many as 1,000 million 

 sterepisomers. If we sssume that serum globulin, myoal- 

 bumin, and other of the highest pmti -ins may each have a 

 similar number, and that the simpler proteins and the 

 fats and carbohydrates, and JHTMHIW other complex ..r 

 ganic substances, may each have only a fraction of tin* 

 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 individ- 

 uals. Furthermore, since the factors which give 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 ss s common index of all. 



' In accordance with the foregoing statement, it can 

 readily be understood how environment, for instance, 

 might so affect the individual's metabolic processes as 

 to give rise to modifications of the constitutions of cer- 

 tain corresponding proteins and other vital molecules 

 which, even though they be of too subtle a character for 

 the chemist to detect by his present methods, may never- 

 theless be sufficient to cause not only physiological and 

 morphological differentiations in the individual, but 

 also become manifested physiologically and morphologi- 

 cally in the offspring. 



' Furthermore, if the corresponding proteins and 

 other complex organic structural units of the different 

 forms of protoplasm are not identical in chemical con- 

 stitution, it would seem to follow, as a corollary, that 

 the homologous organic metabolites should have specific 

 dependent differences. If this be so, it is obvious that 

 such differences should constitute a preeminently im- 

 portant means of determining the structural and physio- 

 logical peculiarities of protoplasm. 



"'It was such germinal thoughts that led to the 

 present research, which I began upon the hypothesis 

 thst if it should be found that corresponding vital sub- 

 stances are not identical, the alterations in one would 

 doubtless be associated with related changes in others, 

 and that if definite relationships could be shown to 

 exist between these differences and peculiarities of the 

 living organism, a fundamental principle of the utmost 

 importance would be established in the explanation of 



VII 



