NOVEMBEE 6, 1914] 



SCIENCE 



651 



that is, capable of being used by certain low 

 organisms as food, but not all are thus avail- 

 able, and, moreover, those which are show 

 marked differences in the degree of fermenta- 

 bility. In the case of other substances Peni- 

 dllium may consume the laevo form, but not 

 the dextro form. Other organisms show similar 

 selectivities, using either dextro or Isevo form, 

 or both, but in the latter case in unequal 

 degree. Even more striking instances have 

 been recorded in the actions of poisons, as, for 

 instance, dextro-nicotine is only haK as toxic 

 as the Isevo form; dextro-adrenalin has only 

 one twelfth the power of the Isevo form; 

 racemic-cocaine has a quicker and more in- 

 tense but less lasting action than the Itevo 

 form; the asparagines, hyoscines, hyoscya- 

 mines and other substances have been found 

 to exhibit marked differences in accordance 

 with variations in their optical properties. 

 With other bodies belonging to this category 

 it may be found that one form is sweet while 

 another is tasteless; another may be odorous, 

 but its enantiomorphous form without odor. 



To the foregoing there may be added exam- 

 ples of other substances that exist in several 

 forms, but which physico-chemically belong 

 to a different class. Thus, nitroglycerine may 

 exist in forms that are so different that under 

 given conditions of temperature and percus- 

 sion one is explosive and the other non-explo- 

 sive. Differences in substances which are 

 found in allotropic forms may be as marked 

 as in any of the preceding illustrations, as, for 

 instance, in the ease 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 ortho, meta and para 

 forms of a given substance may exhibit more 

 or less marked physiological and toxicological 

 variations, and so on. 



The explanation of the remarkable differ- 

 ences shovm by these substances, which differ- 

 Hices are paralleled by those manifested by the 

 lethal and innocuous proteins of the serpent, 

 the pepsins, the protamins and the red blood 

 corpuscles is to be found in the results of two 

 independent but intimately related lines of 



physico-chemical research: (1) The investi- 

 gations of Van't Hoff and LeBel and subse- 

 quent observers which have laid the founda- 

 tion of a new, and to the biologist and physi- 

 cian an extraordinarily important, develop- 

 ment of chemistry known as stereochemistry — 

 a department that treats of the arrangements 

 of the atoms, groups and masses of molecules, 

 or in other words of intramolecular arrange- 

 ment 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 

 substance or combiRation of substances may 

 exist owing to differences in intramolecular 

 and extramolecular arrangements and concen- 

 tration of their components in relation to 

 temperature and pressure. 



According to stereochemistry a given sub- 

 stance 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 prototsrpe, yet each may have certain 

 properties which positively distinguish it from 

 the others. Theoretically, such substances as 

 serum albumin, serum globulin, hemoglobin, 

 starch, glycogen and chlorophyl may be pro- 

 duced by nature in countless modified forms, 

 owing to differences in intramolecular ar- 

 rangements. Miescher has estimated that the 

 serum globulin molecule may exist in a thou- 

 sand million forms. Substances that exist in 

 such multiple forms of a prototype are dis- 

 tinguished as stereoisomers. The remarkable 

 fact has been noted by Fischer and others 

 that stereoisomers may exhibit as great or 

 even greater differences in their properties 

 than those manifested by even closely related 

 isomers, which latter in comparison with stereo- 

 isomers are distantly if at all chemically 

 related. As already instanced, so slight a 

 change in molecular configuration as gives 

 rise to dextro and Isevo forms may be suffi- 

 cient to cause definite and characteristic and 

 even profound differences in physical, nutri- 

 tive and physiological properties. 



In accordance with the " phase rule " a sub- 



