Horse 

 Pig . 

 Goose 

 Mouse 



It is seen that this relative uniformity of the ratio 

 of basal metabolism to surface area is present even in animals 

 of difterent species. This relationship may be due to the 

 regulation of the rate of metabolism by stimuli from the 

 skin. This is doubtless true so far as heat production to 

 compensate for loss of heat is concerned, since the rate of 

 cooling is directly proportional to surface area. It is probable, 

 however, that metabolism is also dependent upon the mass 

 of active tissue, i.e. muscle, and that this accounts for the 

 relatively small variations found in the ratio of metabolism 

 to surface. 



A comparison of the metabolism in different animals 

 should thus be based on the surface area. In bodies similar 

 in material and shape but differing in size, the surface is 

 proportional to two-thirds the power of the weight. As 

 animals of the same species are relatively constant in shape 

 and composition, the surface area can be calculated from the 

 weight by the following, known as Meeh's formula : — 



S = kW« 

 where " S " = unit of surface, W = unit of weight, 

 " k " = constant for each species. 



The value of " k " for diiferent species has been deter- 

 mined by direct measurement of the surface area and 

 calculating the relationship of unit of surface to unit of 

 weight. Some of the values found are : — 



A direct determination of the extent of body surface of 



