MAMMALIA— PHYSIOLOGY 



441 



Nutrition and Vitamins. — Since 191 1, a great mass of literature 

 has accumulated, largely consisting of the further enumeration of 

 food substances characterized as belonging to groups of vitamins. 

 The wholesale advertising of essential foodstuffs such as milk and 

 green vegetables has resulted most favorably. A fuller appreciation 

 of the virtues of cod liver oil and the tremendous importance of the 

 ultra-violet and infra-red rays has also been a product of vitamin 

 study. But perhaps too much time has been wasted in biological 

 tests of foods long known to be chemically allied. 



Fig. 242//. Rat in advanced stage of xerophthalmia due to lack of Vitamin A. 



(Courtesy of Eli Lilly & Co.) 



Vitamin A is found in cod liver oil, butter, cream, cheese, whole 

 milk, egg yolk, liver, heart and kidneys, spinach, lettuce, cabbage, 

 tomatoes, carrots, sweet potatoes, parsnips, green peas, and many 

 other substances. Deficiency in Vitamin A results in an anemic 

 condition, with failure of ovulation and retardation of growth. The 

 sense organs are diseased and pus laden, the eyes being typically 

 affected by xerophthalmia with conjunctivitis and corneal degenera- 

 tion. Vitamin A is fat soluble. Exposure to the air and forced 

 oxygenation renders it inactive. Commercially canned tomatoes 

 (no oxidation) were as rich in vitamins at the end of three years as 

 fresh tomatoes. While it is generally considered that the vitamin 



