88 
THE VOYAGE OF H.M.S. CHALLENGER. 
If one compares the scapula with the pelvis one recognises that the latter fulfils in 
man a much more important office than the former. The pelvis presents both a 
surface for the attachment of important muscles, and is also the part of the skeleton 
throuo-h which the weio-ht is transmitted to the lower limbs. The forces exercised on it 
are therefore more varied and more powerful than those which bear on the scapula. For 
the latter bone lies comparatively free in the flesh, and has its surfaces and processes 
developed essentially in relation to the various muscles which are attached to it, and it 
is not in man concerned in the transmission of weight. The external forces operating 
on the human scapula, which might lead to a modification in its form and proportions, 
would therefore be mainly, if not exclusively, in connection with its muscular attach- 
ments, more especially those muscles which are engaged in the abduction and elevation 
of the upper limb, and the rotatory muscles of the humerus. Should there be anything 
in the habits of one race of men which might require a particular group of scapular 
muscles to be used and developed to an extent far greater than in another race, then it 
is not unlikely that the area of attachment of those muscles in that race would be widened 
or lengthened to an extent greater than is the case in those races in which the same 
group is not similarly exercised, and the proportions of these parts of the scapula to the 
rest of the bone would in so far be modified. The arboreal habits of the ape require that 
it should use its upper limbs for purposes of climbing, and for swinging itself from one 
branch of a tree to another, so that the muscles engaged in the elevation of the upper 
limb require to be powerful ; which would account for the greater development of the 
supraspinatus muscle and supraspinous fossa, and would probably lead also to the 
greater obliquity of the scapular spine than is the case in man. In a similar manner 
one would expect to find in those races of men, as the Australians, who climb trees in 
quest of food, or those natives of the interior of New Guinea, whose houses are built 
in the upper branches of lofty trees, a commensurate development of the elevatory 
muscles of the upper limb and of their respective areas of attachment. But in connec- 
tion with this development the additional area might perhaps be obtained, either by 
an addition to the length or breadth of the surface, or perhaps both to its length and 
breadth. 
