THE SKELETON. 39 



prevails, and the extremities of the humeri and femora long remain 

 epij^hyses in the frog. 



A final purpose is no doubt, also, subserved in most of the separate 

 centres of ossification which relate homologically to permanently dis- 

 tinct bones in the general vertebrate series ; it has long been re- 

 cognised in relation to facilitating birth in the human foetus ; but 

 some facts will occur to the human osteogenist, of which no teleolo- 

 gical explanation can be given. 



One sees not, for example, why the process of the scapula which 

 gives attachment to the pectoralis minor, the coraco-brachialis, and 

 the short head of the biceps should not be developed by continuous 

 ossification from the body of the blade-bone, like that which forms 

 the spinous process of the same bone. It is a well-known fact, how- 

 ever, that not only in Man, but in all Mammalia, the coracoid process 

 is ossified fi'om a separate centre. In tlie Monotremes it is not only a 

 distinct, but is as large a bone as in Birds and Reptiles, in which 

 it continues a distinct bone throughout life. Here, then, we have 

 the homological, without a teleological explanation of the separate 

 centre for the coracoid process in the ossification of the human blade- 

 bone. 



This distinction in the nature and relations of such centres, which 

 is indispensable in the right application of the facts of osteogeny to 

 the determination of the number of essentially distinct bones in any 

 given skeleton, has never been considered, so far as I know, in that 

 application. Some homologists (ii. xiv.) have gone beyond Cuvier, 

 and still more beyond nature, in arguing the number of individual 

 bones, as indicated by the number of separate centres of ossification 

 in the embryo, to be the same in all vertebrate animals ; and that they 

 afterwards differed, or seemed to differ, only by reason of the greater 

 or less rapidity or extent of the confluence of those ossific centres or 

 essentially distinct bones. 



This primitive conformity of separate osseous pieces in the verte- 

 brate series holds good, however, only in regard to the separate 

 centres of ossification of those bones of higher animals which have 

 homological relations to the permanently distinct bones of lower spe- 

 cies ; it by no means applies to those which have merely teleological 

 relations to the species in which they exist. 



But, besides the epiphyses of the long bones of Mammalia, which 

 enter into the latter category, and cannot, therefore, be properly 

 viewed in the light of distinct bones ; what are we to say to the 

 intercalated, inconstant " ossa wormiana," or to the ossified tendons 

 of birds, or to those developed in the tendons of the vertebral muscles 

 of the musk-deer? Are these to be reckoned equally distinct and in- 



D 4 



