982 The American Naturalist. [November, 
ae : * 
much greater size in proportion to the body than in young cows 
and heifers. They are also poorer, and it requires a much greater 
amount of food to produce a given amount of flesh than in 
younger animals. This case seems to indicate that the efficiency 
of the organ degenerates with increasing size. Of course this is 
not always true, and there are marked instances to the contrary, 
as in the relatively large brains of certain intellectual prodigies 
and the heavy biceps of professional pugilists. Probably the dif- 
ferences of size in the functional organs of the viscera are, in 
many cases, due to the growth of indifferent tissues as fat and 
connective fibers. Perhaps their presence in the case of the cows 
already mentioned may even impede the normal discharge of the 
functions. Be this as it may, it is undeniable that the greater 
quantities of viscera are by so much an added incubus to the 
movements of the animal. It is, of course, self-evident that in 
most cases all the tissues not directly concerned in the contrac- 
tions which produce motion are in some degree adversative to 
such contractions. Only a few of the voluntary muscles are used 
in any one movement, and all the rest of the body is, for the time 
being, a dead weight to be overcome; so that in the simplest of 
our daily movements the active and passive parts are continually 
shifting about, and ‘the waves of maximum activity travel now 
here and now there. All the tissues, save the voluntary muscles, 
are perpetually inert relative to movements in the environment. 
They are at one time impelled to passive movements, and at 
another time are quiescent, according to the character of the 
movement. They are in one sense a necessary evil, impeding and 
yet indirectly promoting the movements of the animal. 
Lastly, we have to consider the bones. Without doubt they are 
inert elements. Yet that very inertness serves a useful purpose in 
the animal movements. If we compare the ratios of the bones to 
the body and of the muscles to the body in the woodchuck and 
rabbit, we are surprised at the absence of parallelism which a 
knowledge of their mutual connection would lead us to expect. 
While the muscles of the woodchuck are to those of the rabbit 
relative to the body as 1: 2, the bones are nearly equal in the 
same comparison. This is explained by the fact that the total 


