Nutrition 



133 



are particularly useful to prevent hemorrhages in young chickens, in human 

 infants, and in adults with obstructive jaundice. Vitamin Ki is: 



H 



H<t 



o 



II 



C CH3 



' \ / 



C CH3 



CH:. 



CH3 



CHa 



\ 



C C-CH.CH=C-CH.-CH.-CH-CCH0a-CH-(CH03-CH-CH, 



C 



II 



o 



Vitamin K is not a dietary essential for the cow— it is synthesized in the rumen; 

 also the rat, dog, and probably man obtain enough from bacteria in the in- 

 testine. This is not true for chickens, however, and in mammals shortly after 

 birth the prothrombin level of the blood drops unless the vitamin K level in 

 the maternal blood has been high. The entire molecule is not necessary, for 

 the naphthoquinone is as effective in maintaining blood prothrombin as is the 

 vitamin K with its side chain. 



Fig. 28. Wings of Ephestia in increasing deficiency of linoleic acid from 1 (no 

 deficiency) to 8. From Fraenkel and Blevvett.'" 



Specific Fatty Acids. Most animals grow and live well with little or no 

 dietary fat, but, since fat is the most favorable storage substance, it can be 

 intercon verted to and from carbohydrate and under some conditions to and 

 from proteins; hence fat may be deposited on a high caloric intake even when 

 little fat is fed. This is well shown in the flagellate Chilo-inonas which accumu- 

 lates fat droplets when fed acetate, particularly in the absence of sulfur. In 

 higher animals the deposited fat may differ from the food fat in respect to 

 melting point or degree of saturation. The total fat intake can be reduced to 

 very low levels in birds and mammals. Apparently fats, per se, are not neces- 

 sary in animal diets; however, at least one fatty acid is required by certain 

 animals. Moths of the genus Ephestia require linoleic acid for successful 



