THE SKELETON 



93 



Holl also repudiates the torsio humeri as the most important 

 factor in effecting the torsion of the fore-limb. He, unlike 

 others, considers that there is no very great difference between 

 the position of the bones of the 

 forearm and the fore-leg in Man. 

 He rightly points out that the 

 tibia and fibula do not lie parallel, 

 but that the fibula lies external to 

 and behind the tibia, and insists 

 that it thus occupies, in relation 

 to the tibia, a position similar to 

 that of the ulna in relation to the 

 radius. 1 In instituting these com- 

 parisons we ought to start with *&% ^jj&jd. YJ/ tl -'"}[\\ -f 1 - 

 the hind-limb, which is simply 

 so rotated at its base that the 

 whole of its morphologically ven- 

 tral surface becomes posterior in 

 position, and not with the fore- FlG - GG.-SKELETON OF A YOUNG BEAR 



f. ILLUSTRATING THE POSITIONS OF THE 



limb, the torsion of which involves 

 the independent segments individ- 

 ually, and should therefore be 

 excluded in endeavouring to settle the question of homology. 

 This consideration excepted, Holl agrees in the main with 

 Hatschek as to the Quadrupeds ; but he extends his observations 

 to Man, and declares that if he be regarded as a Quadruped, the 

 changes of position in the limbs are such that the homologising 

 of them with those of Quadrupeds is not difficult, i.e. if a man 

 goes on all fours the position of the shoulder girdle and with it 

 that of the humerus is slightly altered. The head of the latter 

 no longer points forwards, but backwards, and its great tuberosity 

 comes to point forwards, just as in the quadrupedal Mammals, 

 the distinction formerly established between them and Man in 

 this particular thus disappearing. 



1 [Holl appears to have insufficiently appreciated the primary disposition of the 

 limb-buds. The postero-internal displacement of the fibula upon which he lays such 

 stress is well marked in the Marsupials, which, with the exception of the Dasyuridse, 

 have an opposable hallux. Detailed examination of the bones of the fore-leg of 

 some of these animals and of the muscles which control their rotatory (so-called 

 " pronator ") movements, proves that the adaptive modification which the hind-limb 

 has at any rate here undergone is of a distinct order from that of the fore-limb above 

 described (cf. Young, Jour. Anat. and Phys., vol. xv. p. 392). And it may be 

 incidentally remarked that an opposable hallux appears independently among 

 Rodents, in the common Dormouse.] 



LIMBS. (After Hatschek.) 

 1-5, digits ; rd., radius ; ul., ulna ; 

 tb., tibia ; fb., fibula. 



