DIET AND NUTRITION 



maturation, and rupture of Graafian follicles, after which 

 it disappears; but in A-deficient rats the desquamation of 

 cornified cells is continuous and obscures all ovarian cycles 

 that may be present. Vitamin A deficiency does not create 

 a malfunction of the ovaries, for they continue to secrete 

 hormones similar to those in estrus. This effect on the 

 vaginal mucosa of the rat is so pronounced that Evans and 

 Bishop report their ability to detect vitamin A deficiency 

 in otherwise apparently healthy animals receiving enough 

 A to prevent ophthalmia. Raising the level of A in the 

 diet may abolish the persistent cornification of the vaginal 

 epithelium and restore normal conditions. 



In vitamin A deficiency this transformation of epithelium 

 into stratified, squamous keratinizing epithelium is es- 

 pecially pronounced in the upper respiratory tract, and in 

 the renal pelvis, urinary bladder, seminal vesicles, epididy- 

 mis, prostate, salivary glands, and pancreas. 



When there is deficiency of vitamin A, the intestinal 

 flora is markedly changed as respects gram-negative and 

 gram-positive bacteria in the faeces. The faeces of rats on 

 the deficient diet are dry and hard, which may account 

 for the disappearance of streptococci; otherwise there is no 

 change in the proportion of bacteria which ferment 

 glucose, lactose, and sucrose. The proportion of hydrogen- 

 sulphide-forming bacteria remains constant. 



Under deficiency of vitamin A, rats frequently die of 

 bacterial invasion of the ear and nasal cavities before the 

 appearance of ophthalmia. As the infection advances, it 

 leads to nutritional disaster in which the animal is not 

 restored to a normal condition by feeding rations containing 

 vitamin A. Werkman has reported that a deficiency of 

 vitamin A in the diet increased the susceptibility of rats 

 to anthrax and pneumonia. 



An interesting observation reported by Howe is the 

 reversion of the odontoblasts to osteoblasts when animals 



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