6 QUADllUMANA. 



and the reason is evident, for the axis of the heart (which is much 

 longer in the brute) is in the direction of the body ; therefore the apex 

 is at the diaphragm, and the basis is forward in the thorax. Now, as 

 the auricles are at the basis, and there the veins enter, the inferior 

 vena cava is obliged to pass forwards the whole length of the ventricle 

 to get to the auricle. 



[Subclass Gyrencephala. 



Order Quadrumana.] 



From the structure of the parts of monkeys for progressive motion 

 they are ill adapted for distances on even ground. They are much 

 better adapted for climbing and walking upon uneven ground, where 

 there are banks or risings upon which they can raise their fore-feet 

 higher than the hind. Their walking is very similar to that of a child 

 who has hardly the power of supporting the centre of gravity ; but it 

 must be allowed that these very motions are performed with a clever- 

 ness which takes off the awkwardness. 



They walk on the ends of the metacarpal bones of the hand or fore- 

 foot, which adds to the length of the fore-extremity. The tarsus and 

 metatarsus make a little bend, and then the toes make another angle 

 with the metacarpus ; so that when they walk it is sometimes on the 

 metatarsus with the toes often tilting on the ends of the metatarsus ; 

 but I believe seldom or ever on their tarsus. 



All of the monkey tribe, with all their gradations, as the sanguine l , 

 mongoose 2 , &c, have thumbs on their hind-feet. The great use of 

 this would appear [to be] to fit them better for climbing trees ; for in 

 the act of moving from bough to bough, it is just as necessary that 

 they should hold the bough on which they move their hind-feet, as it 

 is to hold that bough on which they move their fore-foot or hand ; for 

 they do not so much set their foot on the bough, as they lay hold of it 

 and pull themselves up by it. This part is not only of service in climb- 

 ing up but in coming down, if not more so ; for in coming back they 

 can lay hold of a branch to secure themselves : but it is also of singular 

 service in coming down sideways or head foremost, for it supports the 

 body when coming down sideways, by a hand and foot of one side 

 holding above, wbile either the hand or foot, or both, of the other side 

 are in search of a hold below : also when coming down forwards ; for 



1 ['Sangliu' of Edwards's 'Gleanings in Natural History,' p. 15. pi. 218: 

 ' Sagouin,' of Jonston's ' Quadrupeds,' p. 143 : it is a species of Jaechus, probably J. 

 vulgaris, Geoffroy.] 



2 ['Mongooz ' of ' Edwards's ' Gleanings.' &c. p. 12. pi. 216 : it is the Lemur Mongoz. 

 Linn.] 



