Absorption, Metabolism, and the Diet - 351 



malfunction. Moreover, two of the fat-solu- 

 ble group, namely A and D, are the only 

 vitamins that are known to have deleterious 

 effects when taken in great excess. 



Previously the B-complex of vitamins was 

 thought to be a single compound. Now, how- 

 ever, at least ten separate B vitamins have 

 been identified, although not all of these 

 will be discussed. 



A deficiency of thiamine, or vitamin B x , 

 gives rise to polyneuritis, or beriberi, as it is 

 usually called in man. Drastic polyneuritis 

 involves degenerative changes in the nerves 

 and a severe progressive paralysis. The pa- 

 ralysis disappears very rapidly, however, 

 when thiamine is given. A polyneuritic ani- 

 mal frequently regains normal muscular 



Fig. 18-3. Upper photograph: Drastic vitamin A defi- 

 ciency in a white rat, showing blindness as a result of 

 an ulceration of the cornea. Lower photograph: Restor- 

 ation of the eyes after feeding adequate quantities of 

 vitamin A. 



In some cases a deficiency of the fat-soluble 

 vitamins may result, not so much from their 

 lack in the diet, but more from a failure in 

 their absorption. Because bile salts are nec- 

 essary for this absorption, deficiencies may 

 arise in cases of gall bladder or other liver 



Fig. 18-4. Upper photograph: Pigeon suffering from 

 polyneuritis. Lower photograph: Same bird less than 

 3 hours after treatment with thiamine (vitamin B x ). 



