CHEMOTHERAPY 



Classification of substances as inactive is undoubtedly largely a rela- 

 tive matter, since probably almost any surface-active agent worthy of 

 the name would kill bacteria if used in the concentration of around 

 1 % required for phenol and cresol, which are thought of as substances 

 toxic to bacteria. 



The water insolubility of a large portion of the molecule is the 

 driving force that crowds even minute quantities of a surface-active 

 agent out to the boundaries of the aqueous phase. The affinities of 

 this nonpolar group for elements of the bacterial structure determine 

 where upon the cell it will become anchored and to some extent what 

 harm it will do there. The general toxicity of a wide variety of sub- 

 stances in this class suggests that the cellular elements having affinity 

 for hydrocarbon groups do not differ very much from species to species. 

 Evidently, whenever the nonpolar group carries basic or acidic groups 

 along with it the harm it will do may be extensive. If no strongly 

 ionized groups are present, either there is less of the substance adsorbed 

 or its effect is less drastic. Gramicidin, which is a rather insoluble 

 surface-active agent of the nonionizing class, is not notably bacteri- 

 cidal, but does display some specificity and delicacy of bacteriostatic 

 action, as indicated above. Perhaps systematic exploration or syn- 

 theses of further compounds in this general physical class of nonionic 

 agents may offer some promise for those anxious to find new medicinals 

 with some capacity for showing specific action upon cells. 



The special cases of antibacterial agents just considered have 

 caused us to be concerned with cellular attributes of which we fre- 

 quently lose sight. Let us attempt to organize our rudimentary in- 

 formation about cell physiology so that we may see whether there are 

 other possible sites vulnerable to chemical action. We consider most 

 cells to be an organized system of enzymes, most of them at present 

 unkno\Nm, preserved together with vital coenzymes and metabolites 

 within a structural framework the outer boundary of which displays a 

 selective permeability. As indicated in the table on pages 394 and 395, 

 the chemical tasks of the living cell may be classified as several differ- 

 ent, obviously somewhat overlapping, types of function. This tabula- 

 tion wall, one hopes, look very naive indeed in a few years, but it may 

 help us a little now as we try to visualize the problem of exerting 

 chemical control over cells of different types. 



Not only is the understanding of the phenomena under "mecha- 



393 



