INTRODUCTION. 1 1 



Anyone who is familiar with modern biology, general and medical, need not give more 

 than a few moments' thought to the foregoing facts and deductions without being led 

 irresistibly to the application of stereochemistry to the explanation of the infinitude of 

 enzymic actions winch constitute so essential a part of life's processes; of the mechanisms 

 that are concerned in the determination of sex, species, and genera; of the mechanisms of 

 fecundation and heredity; of the changes produced in the labile protoplasm of organisms 

 by the alterations of environment, and their effects on structm'e and function; of the 

 mechanisms which underlie tmnor formation, malformations, and reversions; of the specifi- 

 cities of toxins, hemolysins, and agglutinins; of anaphylaxis; of symbiosis; of bodily idio- 

 syncrasies; of asepsis, infection, and immunity; of the selectivities of different cells and 

 tissues for different substances; of the restrictive activities of hormones in relation to the 

 specific reactive organs; of the specificities of the actions of medicinal substances; of the 

 oft predetermined physiological or pharmacological properties of substances synthetized m 

 vitro; of the extraordinary tolerance of pigeons and dogs to morphine; of the differences 

 in the susceptibility of different species and races of animals to disease; of the seemingly 

 chemical identity of the component parts of different forms of lichens which arise from 

 the same alga;; and of a host of other commonplace and special vital phenomena. 



These statements, as barren as they are of detail and accompanying facts and obser- 

 vations which would add greatly to their interest, applications, and value, must be ade- 

 quate to subserve the purposes for which they are intended: that is, (1) to show by the 

 results of laboratory experience that even trivial changes in the configurations of the 

 molecules of stereoisomers may cause more or less marked, or even profound, alterations 

 in the properties of substances in theu* relations to protoplasm, and of protoplasm itself; 

 (2) to show that different forms of organisms exhibit specific selectivities for substances 

 in accordance with the configm'ation of the molecules, some organisms utihzing the racemic 

 form and others the Isevo or dextro form, or both, but with different avidities, and also 

 that in a given organism one form is complementary, as it were, to one kind of protoplasm, 

 but not to another; and (3) to give evidence which leads to the inevitable deduction that 

 if there be, as justifiably held, countless stereoisomeric forms of starch, each form differ- 

 ing, however little, in its configuration from that of the others, each must have specific 

 individual properties by which it can, by appropriate means, be absolutely distinguished 

 from the others, whatsoever the number. 



Pasteur, in explanation of the selectivity of Penidllium glaucum for dextro-tartaric 

 acid, likens it to the mechanical relations of "male and female screws." Fischer, to whom 

 we owe more than to any other individual for our conceptions of the actions of enzymes, 

 states that the explanation of the selectivities of these mysterious entities probably rests 

 in the complementary configurations of the enzymes and the bodies acted upon, an enzyme 

 not affecting any substance that has not a molecular configuration complementary to its 

 own, or, figm-atively speaking, when the adjustments are not like those of "lock and key." 

 Ehrlich would conceive of a similar complementary relationship between the configura- 

 tion of the toxine and that of the protoplasm. And thus one might go on, but this would 

 take us far beyond the necessary restrictions of this memoir. 



Yet a final word : The history of starch from the moment of the utilization of carbon 

 dioxide and water to form an aldehyde, through the various steps of synthesis of mono- 

 saccharoses, disacchai'oses, and polysaccharoses to the ultimate appearance of starch, and 

 the reversal of these steps when the starch is consumed as food, is upon logical grounds con- 

 ceived to be one continuous and consecutive enzyme action. The enzymes synthetize starch 

 and its precursors, and no other substances, because they can build up only such chemical 

 structures as have configurations complementary to themselves, each tending naturally to 

 build those forms which have the closest configuration; and likewise each analyzes only 

 such substances as have the same stereochemic relationships. If, as stated, protoplasm uses 



