HYPOVITAMINOSIS A (aVITAMINOSIS a) 593 



co-workers '°2^ are of the opinion that, in human subjects, this is a practical 

 problem only when appreciable quantities of mineral oil are taken at meals. 

 Doses of 2.5 ml. of mineral oil three times daily at mealtime did not affect 

 the absorption of vitamin A, nor was there any interference when 30 ml. of 

 the oil were taken at bedtime. 



10. Hypovitaniinosis A (Avitaminosis A) 



(1) Introduction 



The first indication that a nutritional adjunct is necessary for growth in 

 addition to protein, carbohydrate, fat, minerals, and water came as a re- 

 sult of the deficiency symptoms of animals receiving diets which we now 

 know were devoid of vitamin A. Although the first evidence of defi- 

 ciency involves such generalized symptoms as poor groAvth, unthrifty ap- 

 pearance of the skin, and especially of the fur, and infertihtj^, a series of 

 specific deficiency effects can now be attributed to the lack of vitamin A. 

 The morphologic effects of vatamin A deficiency can be demonstrated in 

 many epithelial structures, as well as in the epiphyseal cartilage of growing 

 bones. In the latter structures, changes may occur before any decrease in 

 growth rate is evident. When skeletal growth is retarded, beyond the nor- 

 mal growth period, by lack of vitamin A, it may be resumed after the ad- 

 ministration of vitamin A, long after growth would normally cease. 



The deficiency in the epithelial tissues brought about by a vitamin A de- 

 ficiency is characterized, in growing and adult animals, by keratinization 

 of the epithelia which are renewed by multiplication of the basal cells. 

 The fetus exhibits many types of malformation. All vertebrates examined 

 (including the mouse, rat, guinea pig, fowl, rabbit, dog, fox, pig, cow, mon- 

 key, and man) ^"2®'^*'" require vitamin A or a carotenoid precursor for \dsion, 

 for the maintenance of many types of epithelia, and for the development 

 of teeth and skeletal structure. The most recent (1954) comprehensive 

 discussion on the pathology of avitaminosis A in animals is that of Wol- 

 bach.^"-* Mason made a similar contribution on the effects of vitamin A 

 deficiency in human subjects. ^"^^ 



1"^^ F. Steigmann, H. Popper, H. Dyniewicz, and I. Maxwell, Gastroenterology, SO, 

 587-594 (1952). 



1026 s. B. Wolbach, /. A7n. Med. Assoc, 108, 7-13 (1937). 



10" R. H. Follis, Jr., The Pathology of Nutritional Disease, C C Thomas, Springfield, 

 111., 1948. 



1028 g g Wolbach, Effects of Vitamin A Deficiency and Hypervitaminosis A, in Animals, 

 in W. H. Sebrell, Jr., and R. S. Harris, The Vitamins, Vol. I, Academic Press, New York, 

 1954, pp. 106-137. 



1029 X E. Mason, Effects of Vitamin A Deficiency in Human Beings, in W. H. Sebrell, 

 Jr., and R. S. Harris, The Vitamins, vol. I, Academic Press, New York, 1954, pp. 137-163. 



