94 



ANIMAL MECHANISM. 



the slightest trace to his descendants? Will hereditary- 

 descent make an unique exception with respect to these ac- 

 quired characters ? This appears very improbable, and yet 

 we must admit it, if we negative the development theory. 

 We must bring forward a contrary hypothesis, which would 

 reverse the ordinary laws of hereditary descent, if we refuse 

 to certain anatomical characters the power of becoming trans- 

 missible. 



VARIABILITY OF THE MUSCULAE SYSTEM. 



We have stated that the bony system is subject to external 

 influences, and especially to those of the muscles, which im- 

 press on each' bone the form which we observe in it. The 

 great variety of forms in the skeletons of different animal 

 species corresponds, therefore, with the diversity of their 

 muscular systems. Thus, whenever in animals of different 

 species we find resemblances in certain bones, we may affirm 

 that the muscles which were attached to these bones were 

 also similar. Whenever we observe in an animal, on the 

 contrary, a bone of a peculiar form, we may feel assured of 

 a peculiarity in the muscles which were attached to it. 



But if the muscle and the bone vary simultaneously, what 

 can be the cause which influences them both ? It is under- 

 stood that the skeleton, as it is modified, plays a passive part ; 

 that it is subject to the form imposed upon it by the muscle. 

 But what gives to the muscle itself, an organ eminently active, 

 and the true generator of the mechanical force by which 

 the skeleton is in some degree modified, the particular form 

 which is revealed to us by anatomy ? 



We hope to demonstrate that the power to which the mus- 

 cular system is subjected belongs to the nervous system. The 

 nature of the acts which the will commands the muscles to 

 perform, modifies the muscles themselves, in their volume and 

 their form, so as to render them capable of performing these 

 acts in the best possible manner. And, as this necessity 

 which determines all the actions of animal life, governs the 

 will, it is this, which, according to the external conditions 

 under which every living being is placed, influences its form, 



