FISH AND SHELL-FISH AS FOOD 175 



unlike the familiar strong mineral acids that "eat" 

 metal. Since all proteins are composed of various 

 combinations of these essential amino-acids, animal 

 life cannot exist without an ample supply of all of 

 them. Seventeen of the eighteen common amino-acids 

 are found in fish proteins. Only one, the simplest 

 of the amino-acids and one that can be synthesized 

 by the human body, is not found in the digestion 

 products of fish. All of the amino-acids needed for 

 the construction and repair of our bodies occur in 

 ample proportions. Curiously the composition of fish 

 proteins resembles that of chicken muscle. This fact 

 is especially important when we consider the high 

 nutritive value ordinarily assigned to chicken meat. 

 Fish is an excellent food to supplement a vege- 

 table diet, as it furnishes the amino-acids lacking in 

 cereal proteins. The ability of the Japanese to sub- 

 sist on a vegetarian diet supplemented by fish is 

 attributable to the fat-soluble vitamines found in 

 the fish fats and to certain amino-acids obtained 

 from fish proteins. 



Recently the inorganic constituents of fish and 

 other sea-foods have been recognized as having con- 

 siderable nutritive value. Calcium, phosphorus, 

 magnesium, sodium, chlorine, iodine, potassium, and 

 sulphur are found in all fish. These elements are all 

 required for human nutrition, but all except three 

 of them occur in sufiicient quantities in most foods. 

 Many foods, however, are deficient in phosphorus, 

 calcium, and iodine. 



Canned fish is an especially valuable source of 



