IMPORTANT FOODSTUFFS, IMPORTANT TISSUES 135 



sugar and cream which usually is eaten with them, and which 

 may be considerable. 



Choice of Diet. Much has been written upon the proper 

 choice of a diet. Undoubtedly a mixed diet of wholesome nour- 

 ishing food in sufficient quantity, but not in extravagant excess 

 is the most desirable solution of the problem for the average 

 healthy individual. Different standards of amount will be 

 needed by individuals of different size or different habits of life. 

 For an average sized (70 kilos) city dweller, perhaps 90 grams 

 protein and enough fats and carbohydrates to make the total 

 energy intake about 2,500 calories is about the right amount, 

 but these figures will vary greatly with changing conditions. 

 This subject is discussed in somewhat greater detail in the chap- 

 ter on metabolism. The diet must contain certain unknown sub- 

 stances called vitamines, which will be discussed in the chapter 

 on metabolism. 



Some Important Tissues 



Although the substances occurring in the different tissues have 

 been discussed under the various groups of which they are 

 members, it may be useful from the student's point of view to 

 include here a brief summary or survey of some of the im- 

 portant tissues, and to discuss some additional points of inter- 

 est. 



Muscle. The muscles make up about % of the body weight 

 in adults. They contain about 18-20% protein, 72-78% water 

 and from 0.15-0.3% of glycogen. If muscle tissue is subjected 

 to a very high pressure, a liquid known as the plasma is squeezed 

 out. This represents about 60% of the total muscle weight. 

 The remaining material is called the stroma. The plasma has 

 the power of clotting. The chief proteins of the plasma are 

 myosin and myosinogen (or myogen). Until recently most 

 authors have considered myosinogen to be the mother substance 

 of myosin. This has been disputed, however; it is considered 

 by some investigators to be an albumin. The stroma contains 

 a protein resembling an albuminoid. In addition to the above 



