THE METABOLISM OF VITAMINS 351 



amounts corresponding to 950 to 3,250 c.c. of ox bile, 400 to 1,325 c.c. 

 fresh saliva or 4,150 to 6,000 c.c, of urine; from which the author con- 

 cludes that this vitamin is probably present in comparatively small 

 amounts in saliva, bile and only in traces in urine. Some unpublished 

 experiments by Voegtlin and Myers also indicate that human urine 

 obtained from subjects on a mixed diet is very poor in antineuritic vita- 

 min, as "activated" fullers' earth corresponding to over a liter of fresh 

 urine, when fed daily to pigeons on a polished rice diet, was not capable 

 of delaying the onset of polyneuritis. 



Cooper(c) (1914) showed that alcoholic extracts of feces of rice-fed 

 hens and bread and cabbage-fed rabbits relieved the symptoms of polyneur- 

 itic pigeons. This would indicate that at least part of this vitamin is 

 excreted with the feces. (See also Portier and Random, 1920.) 



That the mammary gland secretes all three vitamins is well established, 

 as feeding experiments with fresh unheated milk has shown that this 

 food belongs to the richest sources of fat-soluble vitamin and that it con- 

 tains also some antiscorbutic and antineuritic vitamin, although the last 

 two factors seem to be present in relatively small amounts. 



The evidence thus far points to the destruction of vitamins within the 

 body, which renders it necessary to constantly replenish the supply through 

 a proper diet. The ultimate source of this supply is the plant, as the 

 animal tissues are unable to produce vitamins. 



Special Features of Vitamin Metabolism 



A discussion of the metabolism of vitamins would not be complete with- 

 out a brief reference to the factors which safeguard an adequate supply 

 of vitamins to the young animal during the period of its life when it 

 is entirely dependent upon the milk of its mother. On the basis of some 

 work on rats, McCollum and Simmonds (1918) conclude that milk varies 

 in nutritive value according to the composition of the food fed the lactat- 

 ing animal. The mammary gland has no power of synthesising vitamins 

 (McCollum, Simmonds and Pitz, 1916). An inadequate supply of fat- 

 soluble and antineuritic vitamin in the diet leads to a corresponding 

 diminution of these substances in the milk. Similar observations were 

 made more recently by Hart, Steenbock and Ellis (1920) with regard to 

 the antiscorbutic vitamin content of milk. They have found that summer 

 pasteur milk is much richer in this factor than dry feed or winter-produced 

 milk. (See also Barnes and Hume, 1919.) Osborne and Mendel(g) 

 (1920) have found little if any difference in the antineuritic vitamin 

 content of cows' milk during the various seasons, an observation which 11 

 easily explained by the fact that the drying of feed does not destroy this 

 vitamin. Further evidence along this line will bo found in the laptc 

 on beriberi. 



