472 



ORGAN SYSTEMS OF MAN 



stored foods soon lose their vitamin C con- 

 tent. The chief symptoms of scurvy are due 

 to the weakening of the walls of the capil- 

 laries and small arteries, causing the char- 

 acteristic bleeding at the joints, gums, and 

 under the skin. Dental caries are supposed 

 to be due, in part, to a low vitamin C 

 intake. 



Vitamin D (calciferol). This vitamin is 

 most abundant in fats that have been ex- 

 posed to ultraviolet light. Such fats are said 

 to be irradiated. Often milk is advertised as 

 being irradiated, which means that some of 

 the fatty substances have been changed to 

 vitamin D. Exposing fats to sunshine will 

 do the same thing; even exposing one's 

 own body to the sun produces this vitamin, 

 hence the name, "sunshine vitamin." When 

 vitamin D is deficient in the diet of children 

 there is failure of proper deposition of 

 phosphorus and calcium in the developing 

 bones, causing the disease known as rickets. 

 A rachitic child has a malformed skeleton. 

 Fortunately very few rachitic children have 

 been seen in recent years, compared to two 

 decades ago. In climates where there is a 

 great deal of sunshine the vitamin de- 

 ficiency is rarely seen. However, in north- 

 ern climates during the winter months 

 children are very apt to deplete their 

 stores of vitamin D. For that reason, it is 

 important that children's diets be supple- 

 mented with this vitamin during this 

 season. 



Vitamin K. Vitamin K is produced by 

 bacterial action in the digestive tract and 

 if interfered with in any way, the vitamin K 

 content of the blood drops, and with it the 

 ability to clot properly. This vitamin seems 

 to play a part in the synthesis of pro- 

 thombin, an essential factor in coagulation 

 of the blood. When bile fails to reach the 

 digestive tract, as in gall stone occlusions, 

 the bacteria do not produce vitamin K in 

 sufficient quantities to allow normal clotting 

 of blood, thus making surgery hazardous. 

 Today the surgeon does not worry, because 

 a few treatments of vitamin K restores the 



clotting time and bleeding is no problem. 

 It is also given before childbirth in order 

 to prevent unusual hemorrhaging. 



Recently, many other vitamins have been 

 discovered, some of which seem to be im- 

 portant in the treatment of disease, and 

 which may or may not have a direct rela- 

 tion to nutrition. For example, folic acid 

 and vitamin B12 are important in the treat- 

 ment of pernicious anemia, a serious blood 

 disease. It has been found that as little as 1 

 microgram ( l,(X)0,000th of a gram per day) 

 of vitamin B12 is adequate to keep a 

 pernicious-anemia patient in good health. 

 As other vitamins are discovered and as the 

 mechanism of their operation in the body is 

 explored, it may be that important new 

 remedies will be found for some age-old 

 diseases. This is a rapidly advancing and 

 fascinating field of research today. 



In summing up this problem in a nation 

 where most people are not confronted with 

 the problem of how to get enough food but 

 what kind of food to select, good advice is 

 to eat a highly varied diet. Such a diet 

 should be particularly rich in fresh vege- 

 tables and fruits, with an ample supply of 

 meat, and lesser amounts of the foods high 

 in carbohydrates, such as potatoes, bread, 

 and so forth, which add weight but which 

 have few vitamins. Eat sufficient, but not 

 too much, food. A slightly underfed rat is 

 the healthiest, and there is reason to believe 

 that the same holds true for man. 



The use of alcohol 



It may seem questionable whether the 

 controversial subject of the use of alcohol 

 and tobacco belongs in a general book on 

 zoology, but because of their widespread 

 use, a discussion of these topics is included. 

 So much emotionalism has been connected 

 with the use of alcohol, in particular, that 

 it has been very difficult for a non-scientific 

 person to obtain an unbiased account of 

 the whole problem. Perhaps a few scientific 

 facts about the use of alcohol by man are in 

 order. 



