Chapter XIV 



CONCLUSION 



In the preceding pages, the story of the vitamin B complex has been 

 told in considerable detail. From the point of view of human and 

 animal nutrition, the survey has indicated the paramount importance 

 of aneurine, riboflavine and nicotinic acid, notwithstanding the fact 

 that these substances may sometimes be synthesised in the intestine 

 by the bacterial flora. Pyridoxine and pantothenic acid would appear 

 to be of less importance, whilst the other members of the complex 

 are probably never responsible for serious deficiency diseases in 

 man or, for that matter, in animals, except under very artificial 

 conditions. 



As has already been pointed out, however, the association with 

 deficiency diseases, although of great importance for the physical 

 welfare of mankind, is by no means the most important characteristic 

 of the vitamin B complex when an attempt is made to assess its sig- 

 nificance in biochemistry ; for the appearance of a deficiency disease 

 depends on an unusual combination of circumstances (page 584). 



The real significance of the vitamin B complex was appreciated 

 more fully when its importance in the nutrition of micro-organisms 

 came to be recognised, although the presence of the whole vitamin B 

 complex in yeast and liver, both centres of intense metabolic activity, 

 was suggestive, and work on the stimulation of tissue respiration by 

 the B vitamins had already indicated their close association with 

 enzyme reactions. The stimulatory action of these substances on the 

 growth of micro-organisms, however, revealed their fundamental 

 importance for living organisms of all types. 



It is now clear that the vitamin B complex is an assemblage of 

 biologically related substances that are essential for the metabolic 

 activity of all living cells, and that their close association in yeast and 

 liver is no mere accident. The fundamental role of riboflavine and 

 nicotinic acid in effecting the transfer of hydrogen from substrates to 

 molecular oxygen has already been discussed in Chapters III and IV. 

 In the absence of these two substances, the dehydrogenation of a 

 large number of substances cannot take place. Just what this means 

 can best be appreciated by a consideration of the processes whereby 

 glucose is transformed into carbon dioxide and water. 



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