APPLICATIONS OF RESULTS Or 



161 



found that <>!)!> f<>rm is sweet while toother is tasteless; 

 another may be odorous, but its enantimorphou form 

 without <>dor. 



To tli.- foregoing there may le added examples o( 

 other substance- t 1 



phy.'inM hemieally In-long to a different claM. Thus. 

 nitroglycerine ma\ forms that are so dilT 



that umliT given roii.litM.n-i of teni|H-rature ami j>ercus- 

 ,>l<wive ami the other ii"ii cxpl.i.-nc. l>if- 

 f.Tencf* in si! ;r.- f.>utiil in allotnpic 



forms may be as marked as in any of thr pr.-ocding illus- 

 trations, a.-, for in.-tance, in the case of phosphorus, which 

 is familiar as the \ellow. white, hlack, and red varieties, 

 all of which with the exception of red phosphorus are 

 lingly poisonous, while the latt. r is inert. The 

 ortho, metu, an.l para forms of a given substance may 

 fxhil.it more or lesa marked physiological and toxicologi- 

 cml variations, and so n. 



Tlie explanation <>f the remarkable differences shown 

 .ese substances, which differences are paralleled by 

 tboae manifested by tlie lethal and mocuous proteins of 

 the sT]..-nt. the pepsins, the protamins and the red-blood 

 i <>r|iuitcle8,i8to l- found in the result* of two ind<-|>< intent 

 but intimately related lines of physico-chemical re- 

 search : ( 1 ) The investigations of Yaii't HolT and LeBcI 

 and subsequent observers which have laid the foundation 

 of a now, and to tlie hi.ilogist and physician an extra- 

 ordinarily important, development of chemistry known 

 aa itereochenii-try 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 \Villard 

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

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



or combination of substances may exist owing to 

 differences in intramolecular and extra molecular ar- 

 r.iii.'. ni.-m- and MMMrintftt -f tli.-:r MBpOMBti 111 

 relation to temperature and pressure. 



According to stereochemistry a given substance may 

 n multiple forms dependent upon differences in the 

 configuration of the molecule, all of which forms have 

 miuon the fundamental chemical characteristics of 

 a given prototy|>e. yet each may have certain properties 

 which positively distinguish it from the others. Theo- 

 retically, such substances as serum albumin, serum glo- 

 bulin, hemoglobin, March, glycogen, and chlorophyl may 

 be produced by nature in countless modified forms, owing 

 to differences in intramolecular arrangements. Miescher 

 haa estimated that the serum globulin molecule may exist 

 in a thousand million forms. Substances that exist in 

 u. h multiple forms of a prototype an 1 di-tinirui-hed as 



isomere. The r.-mnrkable fact has been noted by 

 I.T and others that stereoisomers may exhibit as 



great or even greater differences in thoir properties 

 than tli..-.- manifested by even closely related isomere. 

 which hitter in comparison with stereoisomers are dis- 

 tantly if at all chemically related. A- already instanced, 

 so alight a change in molecular configuration aa gives 

 rise to dextro and la>vo forms may be sufficient to cause 

 definite and characteristic and even profound differences 

 in physical, nutritive, and physiological properties. 



In accordance with the "phase rule" .1 sut^tance 

 or a combination of substances may eii-t in the form of 



geneoua or homogeneous systems,'* 



-\-t.lll c..ll-1-tlllg of a llUIIli.T .."i holu-il.vn.-oll-. .\.tcIIM. 



each of which latter is a manift- .dual 



phase and distinguishable from the others by ph 



M:. al. chemical, or physiological properties. The 

 number of phases of a heterogeneous system increases 

 with the number of component systems and the number 

 of the latter is in direct rclation-hip to the numl 

 independent variable conntit l.y means 



of variationa of either or Mli intramolecular or . 

 molecular arrangement the numU-r of forms of a sub- 

 stance or combination of substances may range from 

 few to infinite. 



Our means of differentiating stereoisomers are, on 

 the whole, limited, and for the most part crude, and 

 while it has been found that differences so marked as 

 those referred to may be detected by the ordinary pro- 

 cvdures, it seems obvious that the inherent limitations of 

 such methods render them inadequ a large 



numlHT of stereoisomerides or related bodies which may 

 exhibit only obscure modifications are to be definitely 

 differentiated, so that other and more sensitive methods 

 must be sought, or at least special methods that are 

 adapted to exceptional conditions. The results of much 

 preliminary investigation in this direction l.-d in one 

 research to the adoption of the crystallographie 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 exhibit corresponding diffen-nees in cr 

 line form and polariacopic |>r<>perties; and, moreover, 

 that the " optical reactions may be found to lie as 

 distinctive and as exact analytically as the react in- 

 obtained by the conventional methods of the chemist. 

 Furthermore, the necessities of the hypothesis dem.r 

 the selection of a substance for study of a diameter 

 which upon theoretical grounds might be exjiocted to 

 n nature widely distributed and readily procura- 

 ble, and, as a con- m was -.!., tod. 



In the study of the hemoglohin* the author had as a 

 co-worker Professor Amos Peaalee Brown.* Hemoglo- 

 bins were examined from over 100 animalx, representing 

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

 the data recorded certain facts are especially conspic- 

 uous, among which may be mentioned the followin 



1. The constant recurrence of certain angles, plane 

 and dihedral, in the hemoglobins of various species, even 

 when the species are widely separated and the crystal* 

 belong to various crystal systems. This feature indi- 

 cates a common structure of the hemoglobin molecules, 

 whatever their sour 



2. The constant recurrence of certain type* 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 genns 



: to a crystallographic group. When their charac- 

 ters are tabulated they at once recall crystallogrn 

 groups of inorganic compounds. The crystals of the 

 genns Felit constitute an isomorphous group which is as 

 \ isomorphous as the groups of rnombobedral and 

 rhomhic carbonates among minerals, or the more 



CWMM In* WMk. Pub No 116 



