APPLICATIONS OF RESULTS <>F KKSKAK< IIKS. 



361 



found that one form is sweet while anothei teless; 



another may be odorous, but its enantioinorphou- I >rm 

 n nhout odor. 



To the Eoreg g there may he added examples of 



other substances that exist in several forms, hut which 

 physico-chemieally helong to a different class. Thus, 

 nitroglycerine may exist m forms that are .so different 

 that uniler given conditions of temperature ami percus 

 sion oni' is explosive and the other non-explosive. Dif- 

 ferences in substances which are found in allotropic 

 forms may he as marked as in any of the preceding illus- 

 trations, as, for instance, in the case of phosphorus, which 

 is familiar as the yellow, white, black, and red varieties, 

 all of which with the exception of red phosphorus are 

 exceedingly poisonous, while the latter is inert. The 

 ortlio, meta, and para forms of a given substance may 

 exhibit more or less marked physiological and toxicologi- 

 cal variations, and so on. 



The explanation of the remarkable difference- Bhown 

 by these substances, which differences are paralleled by 

 those manifested by the lethal and inocuous proteins of 

 the serpent, the pepsins, the protamine and the red-blood 

 corpuseles,isto be found in the results of two independent 

 but intimately related lines of physico-chemical re- 

 search: (1) The investigations of Yan't llolf and LeBel 

 and subsequent observers which have laid the foundation 

 of a new, and to the biologist and physician an extra- 

 ordinarily important, development of chemistry known 

 as stereochemistry — a department that treats of the 

 arrangements of the atoms, groups and masses of mole- 

 cules, or in other words of intramolecular arrangement 

 or configuration of molecular components in the three 

 dimensions of space. (2) The investigations of Willard 

 Gibbs and others which have given us the " phase rule," 

 which defines the phases or forms in which a given sub- 

 stance or combination of substances may ex ist owing to 

 differences in intramolecular and extramolecular ar- 

 rangements and concentration id' their components in 

 relation to temperature and pressure. 



According to stereochemistry a given substance may 

 exist in multiple forms dependent upon differences in the 

 configuration of the molecule, all of which forms have 

 in common the fundamental chemical characteristics of 

 a given prototype, yet each may have certain properties 

 which positively distinguish it from the others. Theo- 

 retically, such substances as serum albumin, serum 

 hulin, hemoglobin, starch, glycogen, and chlorophyl may 

 be produced by nature in countless modified forms, o 

 to differences in intramolecular arrangements. Mie 

 has estimated that the serum globulin molecule may exist 

 in a thousand million forms. Substances that exist in 

 such multiple forms of a prototype are distinguisl 

 stereoisomers. The remarkable fact has been noted by 

 Fischer and others thai stereoisomers may exhihit as 

 great or even greater differences in their properties 

 than those manifested by even closely related i- 

 which latter in comparison with stereoisomers are dis- 

 tantly if at all chemically related. As already instanced, 

 so slight a change in molecular configuration as gives 

 rise to dextro and lasvo forms may he sufficient to cause 

 definite and characteristic and even profound differences 

 in physical, nutritive, and physiological properties. 



In accordance with the "phase rule" a substance 

 or a combination of substances may exist in the form of 



hetero 



j I- in con i i mi:' of a numbei o 

 each of which latter i- a manifestation of an individual 



and distinguishable from the others by phj 

 mechanical, chemical, or physiological pr< The 



number of phases of a heti 

 « ith the number of component - 



of the latter is in direct relation-hip to the number i f 

 indepi ndeiit variable constituents. Therefore, by means 

 of variations of either or both intramolecular or extra- 

 molecular arrangement the number i of a sub- 

 stance or combination of s\t ma. range from 

 few to infinite. 



Our means of differential ing sten - are, on 



the whole, limited, and for the mo.-t pari crude, and 

 while it has been found that differ* i marked as 



those referred to may be detei ted by the ordinary pro- 

 cedures, n seems obvious thai the inherent limitatio 

 such methods render them inadequate where a large 

 number of stereoisomerides or related bodies which may 



exhihit only obscure i Mirations are to be definitely 



differentiated, so tha e sensitive methods 



must he sought, or at least special methods that are 

 adapted to exceptional conditions. The results of much 

 preliminary investigation in this direction led in one 

 research to the adoption of the crystallographic method, 

 especially the use of the polarizing microscope, which 

 in its very modern developments of analysis has demon- 

 strated that substances which have different molecular 

 structures exhihit corresponding differences in er 

 line form and polariscopic properties; and, moreover, 

 that the "optical reactions" may be found to be as 

 distinctive and as exact analytically as the reactions 

 obtained by the conventional methods of the chemist. 

 Furthermore, the necessities of the hypothesis demi i 

 the selection of a substance for study o racter 



which upon theoretical ground- 1 to 



exist in nature widely distributed and readily procura- 

 ble, and, as a consequence, hemoglobin was selected. 



In the study of the hemoglobins the author had as a 

 co-worker Professor Amos Peaslee Brown.* Hen 

 bins were examined from over 100 animal-, representing 

 a large variety of species, genera, and families. From 

 the data recorded certain facts are especiall] 

 uous, among which may be mentioned the following: 



1. Th n-iaiit recurreni tain angles, plane 



and dihedral, in the hemoglobins of various species, even 

 when the species are widely separated and the crystals 

 belong to various crystal systems. This feature indi- 

 cates a common structure of the hemoglobin molecules, 

 whatever their source. 



2. The constanl recurrence of certain types of twin- 

 ning in the hemoglobins, and the prevalence of mimosie. 

 This has the same significance as the foregoing. 



3. The constancy of generic characters in the crys- 

 tals. The crystals of the various species of any genus 

 belong to a crystallographic group. When their charac- 

 ters arc tabulated they at once recall crystallographic 

 groups of inorganic ci n I rystals of the 



Is constitute an isomor] iup which is as 



strictly isomorphous as the groups of rhombohedral and 

 orthorhombic minerals, or the more 



♦Carnegie Inst. Wash. Pub. No. 1 1 » » - 



