90 



ANIMAL MECHANISM. 



ing animals is scarcely recognizable, so thickly is it studded with 

 ridges and projections, each of which gave insertion to a 

 powerful muscle. 



The skull and the lower jaw in the carnivora bear the traces 

 of a powerful muscular action. In the skull a deep hollow 

 retains the impression of enormous temporal muscles ; all 

 around the temporal depression, decided ridges were the solid 

 points of attachment of the muscle ; again, a strong and long 

 apophysis by the side of the lower jaw shows the violent 

 tractile force to which it has been subjected in the efforts of 

 mastication. 



If the effects of muscular actions on the bones augment with 

 the intensity of the force of the muscles, they do not vary less 

 in proportion to the duration of their action. From infancy 

 to old age, the modification of the skeleton goes on more and 

 more, and even allows us, to a certain degree, to determine 

 the age of the subject. 



Mons. J. Guerin has shown that in the old man the verte- 

 brae have longer apophyses, the ribs more angular curves, &c. 

 Compare the cranium of a young gorilla with that of an adult 

 animal ; the form will appear to you so different that unless 

 you had been told that the two skulls belonged to animals of 

 the same species, you would scarcely have believed it. Of a 

 rounded form in the young gorilla, it changes its shape in 

 the adult ; it assumes a kind of ridge like the crest of a 

 helmet ; this is the apophysis into which the temporal muscles 

 are inserted. We should never finish if we were to point 

 out all the modifications to which the skeleton is subjected 

 in different species of animals ; modifications which from the 

 beginning to the end of life become more and more marked. 



Medicine, in its turn, furnishes us with curious information 

 as to these questions, by showing us the sudden development 

 of accidental apophyses which are called exostoses. In certain 

 maladies which attack the entire body, we see the skeleton 

 covered, in a great number of points, with accidental osseous 

 projections ; and almost all these prominences are developed at 

 the points of attachment of the muscles, and as they increase, 

 they extend especially in the direction in which muscular 

 traction is applied. 



