THE SKELETON 73 



The close connection between the increased efficiency of 

 the fore-limbs and the stronger development of the clavicle 

 has already been pointed out ; and the great physiological 

 significance of the clavicle is further shown by the fact, that 

 at a certain stage in development it is the strongest por- 

 tion of the whole human skeleton and the first to become 

 ossified. 1 



One distinction between the shoulder and the pelvic 

 girdle, evident even on superficial comparison, lies in the more 

 limited capacity of movement of the latter, which is in turn 

 associated with the more limited movements of the hind-limbs. 

 But although mechanical causes, connected with the upright 

 mode of progression, certainly play a great part in determining 

 the condition of the latter, they do not furnish the complete 

 explanation, as a similar immobility of the pelvis is found 

 in the lowest terrestrial Vertebrates, Eeptiles, and Amphibians. 

 And further, as in both of these, and especially in the tailed 

 Amphibians, no great distinction is found between the mobility 

 of the anterior and the posterior limbs, the first cause of the 

 distinction so marked in Man must therefore be sought elsewhere. 

 It seems to me to lie, on the one hand, in functional adaptation 

 of the pelvis to the requirements of reproduction, and on the 

 other, in the fact that the distal part of the pelvis forms the 

 functional posterior end of the trunk. At this part of the body, 

 where the posterior apertures of the urinogenital and alimentary 

 systems occur, a firm framework is needed for the related con- 

 vergent viscera. Such a framework would be a predisposing 

 factor in the development of the powerful sphincter and limb 

 muscles, furnishing the latter with a more extensive and firmer 

 surface of attachment, which could further be turned to account 

 by the free posterior limbs. 



The relationships of the pectoral and pelvic girdles to the 

 vertebral column are essentially alike in principle. In neither 

 case, among terrestrial Vertebrates, is the connection attained 

 directly, but always through the intervention of ribs. The 



example, on comparison of the Sea Lion (Otaria) and Great Ant-Eater (Myrmcco- 

 phaga), in the former of which the prcscapular lamina far exceeds in area the rest of 

 the blade-bone. The Sea Lion uses its fore-limb as a swimming organ, the Ant-Eater 

 for tearing up Termites' nests and digging.] 



1 In the scapula of the Veddahs, the greater slant of the spine towards the 

 posterior edge, and the consequent greater development of the supiaspinous fossa 

 (prescapular lamina) as compared with that of Europeans, may be indicated as 

 primitive features (Sarasins). 



