PROBLEMS OF PHYSIOLOGICAL CHEMISTRY. 161 



formulated, connecting given lines of physiological action with a definite 

 chemical structure. Thus, it is well understood to-day, for example, 

 that all substances which contain a nitro or nitroso group united with, 

 or bound to, oxygen have the effect of dilating blood vessels, while, on 

 the other hand, substances which contain the same nitro or nitroso 

 group joined to carbon have a quite different physiological action, 

 being mostly blood poisons. Further, nitrils, E. Cin~, tend to produce 

 ccma, while isonitrils, R. N" = C, are much more toxic and tend to 

 produce paralysis of the respiratory center.* In other words, it is 

 clearly manifest that certain definite groupings within the molecule 

 are the cause of the physiological action of the molecule. At the same 

 time, it is also known that in order to have the physiological action of a 

 substance manifest not only must it contain the necessary group or 

 groupings, but there must likewise be present a second group which has 

 the power of combining with and holding fast to the tissue upon which 

 the physiological action manifests itself. Slight chemical alteration 

 of a substance may, therefore, interfere with or nullify its ordinary 

 physiological action without necessarily altering the physiologically 

 active groups; but by simply changing these other groups through 

 which the molecule ordinarily attaches itself, so that the latter can no 

 longer adhere to the cell substance or tissue protoplasm, there occurs a 

 consequent loss of physiological action. 



Another fact clearly understood is that two substances having 

 the same nucleus and like side chains, with an entirely similar group- 

 ing, may still be physiologically unlike, owing to a different arrangement 

 in space. This is well illustrated by the dextro- and lsevo-rotary tar- 

 taric acids, one of which is readily utilized by Penicillium glaucum as 

 nutriment, while the other can not be so consumed. Many other illus- 

 trations might be cited, especially with various types of organic poisons, 

 all tending to show that physiological action is dependent upon the 

 arrangement of the atoms or radicles in space, as well as upon the 

 nature of the atoms or radicles. With these facts before us, we see 

 many lines of inquiry presenting themselves, many problems demand- 

 ing solution, with reference both to pharmacology and physiology. 



Confining our attention more especially to physiological matters, we 

 are certainly justified in considering the application of these principles 

 to many of the substances conspicuous in the processes of the body. 

 The work and suggestions of Pasteur and Emil Fischer have indicated 

 certain possibilities regarding the nature and action of enzymes, not 

 to be overlooked. Stereochemical configuration may be just as much 

 responsible for enzyme action, for proteolysis, amylolysis, etc., as any 

 other feature of the active molecule, and how far other lines of physio- 



* See Frankel, ' Ergebnisse der Physiologie,' Dritter Jahrgang. Biochemie, 

 p. 291. 



