26 THE BIOCHEMISTRY OF B VITAMINS 



case, 58 per cent of the values differ by less than a factor of two from the 

 average value for the vitamin in question, whereas for Table 1, 60 per cent 

 is the corresponding figure. These data seem to indicate that insofar as 

 the content of the various B vitamins can be taken as an index of meta- 

 bolic characteristics, the diversity of these characteristics is just about as 

 great for the various tissues of a mammal as it is for the various organisms 

 in the whole biological kingdom. 



Unfortunately, data comparable to that given in Tables 1 and 2 are 

 lacking for each of the vitamins other than those belonging to the B 



* Too much reliance should not be placed upon the exact numerical values, since incomplete extractions 

 and other limitations are involved in connection with the methods used. The material given represents 

 the only data on the subject that is available. 



family. From the fragmentary evidence available we can be reasonably 

 sure that both vitamin A and vitamin C would be found to be absent from 

 a number of the sources listed in Table 1. Insofar as data are available, 

 it appears that ascorbic acid is present in all adult human tissues; but 

 the presence of vitamin A has not been demonstrated in the epithelial 

 layers of the skin, in ovaries after menopause, in testicles before puberty 

 or after involution, in the normal duodenal mucosa, etc. 42 The complete 

 absence of vitamin A from the livers of some animals has been reported, 59 

 and tremendous variation in tissue content is common. In this respect, 

 the quantitative distribution of vitamin A shows a strong contrast to that 

 of the B vitamins. 



Distribution of B Vitamins in Tumors 



The quantitative distribution of the B vitamins in cancerous tissues 

 is interesting both from the standpoint of the B vitamins and because of 

 the light that it sheds on the cancer problem. In a series of 23 human 



