118 TIIK MAMMALIA. 



require tin- Mia>.-ivc proportion^ and structure of 

 tin- hind linil)s, and, reciprocally, that these be- 

 speak a proportionate si/.e and weight of the parts 

 to be sustained ; but why such development of 

 sustaining limbs and parts to be supported in 

 n fi rence to any other action and way of life is 

 inconceivable. The excess of bone in the hind 

 part of the skeleton once recognised as relating to 

 the fixed point of attachment of muscular forces 

 working the fore limbs to the exertion of power 

 adequate to prostrate a tree and the rest of the 

 bony organisation becomes intelligible. That of 

 the hind foot has been explained : the concomitant 

 extent of the muscular origin afforded by the broad 

 scapular plate, with its many ridges, crests, and 

 processes, is thereby accounted for. The necessity 

 of the firmness imparted to the shoulder joints by 

 the perfect clavicles abutting at one end against 

 a large " manubrium," at the other end against the 

 conjoined acromion and coracoid, becomes obvious. 

 Tlu- fore foot retained three huge claws to effect an 

 adequate grasp of the trunk or bough : for their 

 due and varied application the fore arm enjoys al 

 the variety and freedom of movements which an 

 arm terminated by a hand possesses. A tree being 

 prostrated and its foliage thus brought within 



