Vir. VITAMIX A DKFiriFATV I\ A\IM\I,S 113 



and were described in a case of experimental human scur\'y in the presence 

 of an ade(iuate \'itamin A intake.'''' Mici'oscopic hyperiscratosis of hair 

 folhcles and epidermis and al)sence of sebaceous fi;hnuis and edema and 

 homogenization of the elastic tissue and of collaiicii libers are described by 

 H. Montgomery in a single biopsy specimen from a physician who volun- 

 tarily remained on a \itamin A-fi'ee tliet foi- 180 days. Another biopsy 

 taken 17 days after \itamin A therapy was instituted showed normal skin.^^ 

 In animals, the skin I'esponses to vitamin A deficiency have l)een reported as 

 ati'ophy of the epidermis and its appendages. Xo coimective tissue changes 

 have been described. .V re\iew of the writer's extensive material fiom guinea 

 pigs and rats fails to show significant degrees of hyperkeratosis, and cer- 

 tainly no plugging of hair follicles. On the other hand, there is atrophy of 

 the hair bulb and of internal sheath cells in newly foi-med hair follicles. 

 Some contusion has arisen, in regard to desci-iptions of both human skin 

 and animal skins because of the authors' lack of knowledge of the hair fol- 

 licle cycle in relation to hair formation.'' Sulli\an and Evans succeeded 

 in producing in rats some degree of hyperkei-atinization of epidermis and 

 hair follicles by withdrawing vitamin A from rats previously subjected to a 

 diet tleficient in the heat-stable members of the vitamin B group. '^ 



Although the morphologic changes of the epidermis are not impressive, 

 this tissue should be of major importance in endeavors to elucidate the ac- 

 tion of vitamin A because it has precisely the structure which so many 

 epithelia adopt as a specific conseriuence of the deficiency. 



g. Repair of Epithelia in Recovery from Vitamin A Deficiency 



Repair in rats after they are restored to a normal diet is rapid and may be 

 visible in 5 daj's. More rapid results might be obtained now that massive 

 doses in the form of concentrates or crystalline vitamin A are available. Re- 

 pair is presumably initiated by the lowermost layer of cells of the replace- 

 ment epithelium, all of which have proliferative powers as in the stratum 

 germinativum of epidermis. This layer, one to two cells deep, remains in- 

 intact; immediately above it, cells, presumably irreversibly headed toward 

 keratinization, become vacuolated and invaded by polymorphonuclear leu- 

 cocytes, suggesting that both autolysis and heterolysis account for the 

 disappearance of the middle stratum of cells. The upper layer of keratinized 

 cells disappears completely; the lowermost layer proliferates and differ- 

 entiates into epithelium normal for the region. The sequences duplicate 

 accurately those of th(^ rat's \-agina in die^trus. 



'* J. H. Crandon, C. C. Luiul, and D. B. Dill, ^'ew Encj. J. Med. 223, 353 (1940). 

 '6 L. F. Steffens, H. I. Bair, and C. Sheard, Am. J. Ophthalmol. 23, 1325 (1940). 

 '" S. B. Wolbach, Ann. X. Y. Acad. Set. 53, 517 (1951). 

 '* M. Sullivan and \'. J. Kvans, Arch. Dermatol, and Syphilot. 51, 17 (1945). 



