THE FACTORS WHICH MODIFY THE METABOLISM 195 



of the skin of an average man is something less than 2 

 square meters. The minimum metabolism may be said to 

 be in the vicinity of 1000 Calories per square meter. 



The smaller the body, if it is of a certain standard shape, 

 the larger its surface in proportion to the weight. This 

 is an important biologic principle. Mathematically 

 stated it runs as follows : If two animals of similar build are 

 compared with reference to a given dimension, such as 

 length, their weights will vary as the cube and their sur- 

 faces as the square of this measurement. That is, if one 

 animal is twice as long as another it will weigh eight times 

 as much and have four times the surface. Since the body 

 loses heat in proportion to the extension of its surface it is 

 not strange that this is the determining factor for the 

 metabolism. It is surprising nevertheless that animals 

 as unlike as man, mouse, and fowl should evolve heat in 

 nearly equal quantities for a unit of superficial area. 



Broadly speaking, it may be said that men have a greater 

 metabolism than women. When the larger average stature 

 of men is taken into consideration the difference is dimin- 

 ished, but does not wholly disappear. We must recognize 

 that when a man and a woman are equal in weight there 

 are still characteristic features of organization which modify 

 the comparison. Of these the most evident is the greater 

 prominence of subcutaneous adipose tissue in the female 

 figure. When allowance is made for this inactive material, 

 it is plain that for equal weights the woman has less truly 

 living substance to be the seat of metabolism. Her skeletal 

 muscles in particular are very unlikely to make as large 

 a mass as those of a man who weighs the same. The 

 adipose tissue may have a secondary effect also. While 

 its presence means that the metabolism is confined to a 

 more limited system in the woman than in the man, it 

 tends at the same time to economize her heat loss and so to 

 lessen the need of internal oxidation. Such a conception 

 will be more readily entertained when attention shall have 

 been given to the subject matter of the next chapter. 



