METABOLISM 37 



celled animals or may take place through the posterior opening of the 

 alimentary canal in higher forms. 



59. Respiration. — The processes of inspiration and expiration taken 

 together constitute respiration, which includes all gaseous interchanges 

 in the body. 



60. Anabolism and Katabolism. — The processes beginning with 

 ingestion and ending with assimilation are collectively termed anabolism. 

 Anabolism may be defined as the sum of all processes involved in the 

 building up of the body. The processes beginning with dissimilation 

 and ending with expiration and elimination are collectively termed 

 katabolism. Kataholism may be defined as the sum of all processes 

 having to do with the breaking down of the body and the getting rid 

 of the waste matter resulting from it. Egestion, for reasons given in a 

 preceding paragraph (Sec. 58), does not belong under either anabolism 

 or katabolism. 



61. Vitamins. — It has been found recently that providing the body 

 with the necessary kinds and amounts of proteins, fats, and carbohy- 

 drates or of salts and water is not sufficient. Something else is needed 

 to enable it to assimilate the organic foods, and that is the presence of 

 vitamins. These are organic substances of unknown composition that 

 occur in certain natural foods. Vitamin A (fat-soluble) is present in 

 many animal fats, milk, butter, and yolk of eggs but is deficient in vege- 

 table substitutes such as oleomargarine. It promotes growth and perhaps 

 protects the body against rickets. Vitamin B (water-soluble) is found 

 in fruit juices, meat, milk, yolk of eggs, the coverings of grains and other 

 seeds, yeast, and thin-leafed vegetables. It also promotes growth 

 and guards the body from certain inflammatory conditions in nerves. 

 Vitamin C (water-soluble) is contained in citrus fruits, raspberries, apples, 

 beans, cabbages, carrots, turnips, and tomatoes and in liver. It prevents 

 scurvy. Vitamin D (water-soluble and fat-soluble) occurs especially 

 in cod-liver oil. It also prevents rickets, and a deficiency of it leads to 

 an inability to form a properly calcified skeleton. 



62. Energy Changes in Metabolism. — The food taken into the body 

 represents a supply of potential energy. One object of dissimilation is 

 to change part of this into kinetic form in order that the body can make 

 use of it. This kinetic energy appears mostly as heat and as the mechan- 

 ical energy exhibited in movement; a small part appears as electrical 

 energy; and in some cases, in very small part, as light, shown in the 

 luminescence of some organisms. Some of this kinetic energy is neces- 

 sarily used in the securing of additional food, but some is also used in 

 growth, in reproduction, and in carrying on other activities. Among 

 the lower animals the portion of energy used in the securing of additional 

 food is much larger than in the higher animals. The development of 

 efficiency among the latter is, to a considerable degree, connected with 



