
1891.] Quantity and Dynamics of Animal Tissues. 981 
a 
compare two of the animals given in the tables, the woodchuck 
and the rabbit. The ratios of the weight of muscle to the weight 
of body in the two animals stand in the proportion of 1: 2 
That is to say, the rabbit has two pounds of muscle for every one 
possessed by the woodchuck, which it can use in moving its body, 
Now the specific energy of striped muscle in animals as widely 
separated as the bird and man stand only in the insignificant ratio 
of 1200: 1087 (“Animal Mechanism,” E. J. Marey), so that 
we do not feel that we are assuming too great impossibilities when 
we call the specific muscular energies of the woodchuck and 
rabbit equal. Now this equality can only subsist for a period of 
extended duration on condition of equal metabolic activities in the 
two tissues. These activities, in turn, will depend on the food 
supply, digestion, and all the preliminary acts of nutrition. But 
to avoid complications we will adhere to our first assumption. 
. Now the woodchuck has to move twice the inert mass in propor- 
tion to its muscular weight as the rabbit. To do this it can exe- 
cute only one-half the quantity-of motion as the rabbit. Then 
the rabbit leads a life twice as active asthe woodchuck. But the 
viscera of the woodchuck are to those of the rabbit nearly as 
3: 2, and assuming equal nutritive powers in equal weights of the 
viscera, the difference of muscle weight would be partially offset 
by a canceling difference in the rates of repair of the wasting 
tissues. This assumption, however, that equal quantities of vis- 
cera repair equal amounts of waste, is not a safe one. Besides, it 
will be remembered that in these experiments organs as widely 
diverse in function as the brain, lungs, liver, and heart were, to 
avoid confusing details, weighed together and classed as viscera. 
The rate of assimilation and repair of the muscles would clearly 
depend upon the size and activity per unit quantity of the organs 
concerned in the vegetative functions. Organs of different func- 
tion, as the brain (which is extremely variable in size), would viti- 
ate the comparison between equal quantities of viscera as here 
employed. But, what is still more adverse to the assumption, 
there is no good reason for supposing that equal quantities of 
organs discharging the same functions create equal functional 
products. Butchers ~ that in old cows the intestines have a 


