38 LECTURE 11. 



definitions of single bones in antliropotomy, goes so far as to state 

 that, in order to ascertain tlie true number of bones in each species, 

 we must descend to the primitive osseous centres as they are mani- 

 fested in the foetus.* 



According to this rule we ought to count the humerus as three bones, 

 and the femur as four bones instead of one ; for the ossification of the 

 latter begins at four distinct points, one for the shaft, one for the 

 head, one for the great trochanter, and one for the distal condyles. 

 But who will be induced to regard these parts and processes as dis- 

 tinct bones ? No such distinction is kept up in any of the lower 

 classes. In both Birds and Reptiles the femur is developed from a 

 single centre. 



The rule laid down by the great French anatomist fails in its ap- 

 plication to the difiicult point under consideration, because he did not 

 distinguish between those centres of ossification that have homological 

 relations, and those that "have only teleological ones : i. e. between 

 the separate points of ossification of a human bone which typify per- 

 manently distinct bones in the lower animals, and the separate 

 points which, without such signification, facilitate ossification, and 

 have for their final cause the well-being of the growing animal. 

 The young lamb or foal, for example, can stand on its four legs 

 as soon as it is born ; it lifts its body well above the ground, and 

 quickly begins to run and bound. The shock to the limbs themselves 

 is broken and diminished at this tender age, by the divisions of the 

 supporting long bones, — by the interposition of the cushions of 

 cartilage between the diaphyses and the epiphyses. And the jar 

 that might affect the pulpy and largely developed brain of the im- 

 mature animal is further diffused and intercepted by the epiphysial 

 articular extremities of the bodies of the vertebra?. 



We thus readily discern a final purpose in the distinct centres of 

 ossification of the vertebral bodies, long bones, and the limbs of mam- 

 mals, which would not apply to the condition of the crawling reptiles. 

 The diminutive brain in these low and slow cold-blooded animals 

 does not demand such protection against concussion ; neither does the 

 mode of locomotion in the quadruped reptiles render such concussion 

 likely ; their limbs sprawl outwards, and push along the body, which 

 commonly trails upon the ground ; therefore we find no epiphyses 

 with interposed cartilage at the ends of a distinct shaft in the long 

 bones of Saurians and Tortoises. But when the reptile moves by leaps, 

 then the principle of ossifying the long bone by distinct centres again 



* " Mais CCS distinctions sont arbitraircs, ct pour avoir Ic veritable nombrc des os 

 dc chaquc espccc, 11 faut remontcr jusqu' nux premiers noyaux osseux tcls qu'ils se 

 montrcnt duns le foetus." (xiii. torn. i. p. 120.) 



