Chapter VC 



PHYSIOLOGICAL, PHARMACOLOGICAL, AND 

 TOXICOLOGICAL EFFECTS 



The four preceding chapters have presented the available evidence 

 bearing upon the problems of what the B vitamin requirements of living 

 things are, and the metabolic fate of the vitamins themselves, and the 

 next chapter is to deal with the effects of B vitamin deprivation. In ac- 

 cordance with the outline proposed for this section, it is necessary 

 to consider here certain overall effects of the B vitamins on living or- 

 ganisms. 



It is immediately apparent that the major effect of the B vitamins is 

 to maintain the animal and all its parts in an efficient functional state, 

 and regarding this aspect there would seem to be little cause for extended 

 discussion. The exact manner in which the B vitamins function in the 

 maintenance of cellular and tissue metabolism has been considered at 

 length in earlier sections. Moreover, the possible role of the B vitamins 

 in preventing and curing various pathological conditions, primarily 

 avitaminotic and otherwise, is more conveniently discussed in the next 

 chapter, dealing with deficiency states. There are however certain special 

 relationships which exist between the various B vitamins and specific 

 physiological systems and functions, and these require some brief con- 

 sideration at this point. 



In considering the biological effects of any substance it is important 

 to realize that different concentrations of a substance frequently mani- 

 fest markedly different activities. What may be an innocuous and even 

 required substance at one level of administration may become a danger- 

 ous drug at another. There is frequently a distinct intermediate level at 

 which the substance becomes effective in producing in the activity of 

 the organism certain changes which are neither particularly hazardous 

 in the usual sense nor of a nature similar to its physiological function. 

 These three levels of activity — -the physiological, the pharmacological, 

 and the toxicological — are quite distinct for a number of the B vitamins. 

 The cause of the varying activities exhibited by different concentrations 

 of these and other substances is obscure, but it may be surmised that 

 B vitamins in increased concentrations may have two major effects: they 

 may increase the normal physiological reaction to a point where it be- 



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