280 THE VITAMINS 



to the same vitamin-A-free diet at different ages, the average survival 

 periods were as follows : four-weeks-old rats, 63 days ; two months, 

 111 days; three months, 122 days; four months, 148 days; six months, 

 171 days ; nine months, 140 days. 



Thus, on an accurately known diet, which furnishes vitamin A in 

 fairly liberal but not strikingly large proportion, the bodily store as 

 indicated by survival period on vitamin-A-free diet, was found to in- 

 crease steadily up to six months (in the rat) or about the age at which 

 full adult size has been attained. 



That a moderate difference in the vitamin A content of the food, 

 whether during infancy or later life, may result in the acquisition of 

 very significantly different stores of this vitamin by the body was 

 shown by Sherman and Kramer (1924). 



Naturally, regularity of outcome is not to be expected in all cases ; 

 for a striking result of vitamin A deficiency is that it increases the 

 susceptibility of the body to bacterial invasion at many points and does 

 not kill in such a specific way as does, for instance, a lack of vitamin C. 



Wolbach and Howe (1925a) also found that vitamin A deficiency 

 causes a number of pathological changes in addition to those of the eye. 

 These include the presence of abscess-like cavities filled with a yellow 

 cheesy-like material at the base of the tongue, in the pharynx, and 

 in the submaxillary glands. The abnormalities here noted at the base 

 of the tongue are undoubtedly of the same nature as those referred 

 to above as observed by Sherman and Munsell and by Sherman and 

 Storms. Wolbach and Howe found on microscopical examination that 

 the cavities are cysts lined with a stratified keratinizing epithelium and 

 the cheesy mass a mixture of desquamated keratinized cells and leuco- 

 cytes. Their study of the lesions in rats killed at progressive stages of 

 vitamin-A deficiency showed that the principal change is "transforma- 

 tion of various epithelia into a stratified squamous keratinizing epithe- 

 lium. This change is practically constant in the upper respiratory tract 

 including the whole of the nasal passages, larynx, trachea, and bronchi." 

 They also reported that all the salivary glands and accessory salivary 

 glands were found affected, and that similar changes occur late in 

 the pancreas ; and that, in the genito-urinary tract, this transformation 

 into keratinized epithelium is found in the renal pelvis, bladder, seminal 

 vesicles, epididymis and prostate gland. In all of the glands noted 

 there was a considerable degree of atrophy before the change in char- 

 acter of the epithelium takes place. The histological change, charac- 

 terized by transformation of cuboidal into squamous epithelium, they 

 find to be directly due to the nutritional deficiency, infection follow- 



