VII. i:sriM \'i"i(i\' 



.")<)! 



3") to 10 li., arc lc(l a siii I al >!(' ('\|)cii menial lal ion.'' At the end of a depict ion 

 period a\'ci"aji;in«i ('» to 7 weeks, rats show cessation ol }i,rowth and one or 

 more of the specilic syini)toins ol' hiotin delicieiicy. I'liey are then assigned 



I'm,, f). .\iiv;incc I scaly denuatosis in hiotin deficiency involvinti I lie siiovit and 

 whole vciitei'. 



to two or more dosage le\-els of the standard and of each unknown so that 

 rats exhibiting the same degree of deticieucy are distributed equally to 

 each treatment. Pure synthetic biotin may serve as a referenee standard 

 in two or more dilutions. To insure their availal)ility to the rat, despite the 

 avidin in the diet, the biotin sui)plements may be given l)y injection rather 



* D. M. Hegsted, J. J. Oleson, R. C. Mills, C. A. iilvehjeni, and i;. U. Hart, /. Nu- 

 (riliun 20, 599 (1940). 



