30S TJU-: EVOLUTION OF MAN. 



bony parts of tlie limbs are also formed at fii-st from sr)ft 

 uiididerentiated cell-groups of the skin-fibrous layer. These 

 afterwards change into cartilage, and from these the per- 

 manent bones originate by a tertiary process.^^ 



The development of the muscles, or the active organs of 

 locomotion, is, as yet, of much less interest than that of the 

 skeleton, or the passive instruments of motion. The Com- 

 ))aiative Anatomy of these is, indeed, of much higher im- 

 j>oitance than their Embryology. But as very little attention 

 lias, as yet, been j)aid to the Comparative Anatomy and 

 Ontogeny of the nmscular system, we have only very 

 general ideas of its Phylogeny also. The muscular system 

 as a wliole has developed in the most intimate reciprocal 

 correlation with the bone svstem.^^ 



