590 



BIOTIN 



A rat is considered severely deficient when it shows almost complete denu- 

 dation of the skin, "kangaroo" gait, sores and cracking of the skin, particu- 

 larly of the folds under the legs, closure of the eyes, and marked weight 



Fig. 5. Biotin (IcIiciciicN- willi sc;il\ dcnn.'ilDsis, in;iiiil\' in llic neck and ii'''>iii8. 



loss. There may be general exfoliation of the skin in small or larger scales 

 (Figs. 7 and 8). 



It is customary to base the bioassay of biotin in rats on the growth re- 

 sponse, which is expressed more easily in (luantitati^•e terms. In contrast, 

 the curati\'(^ elfcM-t of biolin on cutaneous lesions and the othei- manifesta- 

 tions of biotin deficiency, although more specitic than the growth cfTcM-t, 

 are difhcult to assess exactly. 



Weanling rats, preferal)ly of the same sex and weighing not moic than 



