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 les 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 
the hind-hmb, 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- Fi¢ 66.—SKELETON oF a Youne BEAR 
- ; : : ILLUSTRATING THE POSITIONS OF THE 
limb, the torsion of which involves Lips. (After Hatschek.) 
the independent segments individ- 4% ae eae une 
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 hmbs are such that the homologising 
of them with those of Quadrupeds is not difficult, ze. 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. 
ce 
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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 Dasyuride, 
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. ] 
