M A M M A L I A. 



14.5 



too by which the fore legs are made to cross each 

 other and the paws brought together or to the mouth, 

 give a lateral shape to those joints, and throw more 

 strain upon the muscles than there is in animals 

 which have those joints moveable only parallel to the 

 mesial plane, or with very little lateral motion. The 

 wrist joint is also loose, and the great length of the 

 naked paw which comes to the ground, together with 

 the motion of the thumb, so far as it has motion, 

 being opposed to that of the fingers, makes the 

 planting, and especially the raising of the foot both 

 clumsy and laborious. No animals with perfect cla- 

 vicles are indeed good walkers in straight forward 

 motion, for they have to assist the action of the fore 

 legs by the flexures of the spine, which throw the 

 centre of gravity of the body alternately to the right 

 and left, and thus they may be said to have a double 

 labour to perform, compared with that, which straight 

 forward walkers require in passing over the same 

 extent of absolute distance ; they have to carrv the 

 weight of the body forward, and also to carry it alter- 

 nately right and left. Hence, in bears and several 

 other animals which are riot habitually climbers, but 

 which, though they do climb, spend in general more 

 of their time upon the ground, the clavicles are 

 always more or less imperfect, part of them being 

 composed of cartilage more or less flexible according 

 to the habits of the species. 



The hind legs and feet of the apes have more 

 exclusively a climbing character than the fore ones. 

 They are not used in seizing the food, or in perform- 

 ing any other operation than that of progressive 

 motion, or of holding on upon the branches of trees. 

 The thumbs on them are, generally speaking, articu- 

 lated far in the rear of' the fingers, and turned 

 obliquely inwards, so that they rather grasp against 

 the opposite side of the entire sole of the foot than 

 against the other toes. Those hind feet from their 

 structure take a firm hold upon a branch, and they 

 also afford a broad base for mere support. That 

 base is indeed too broad for walking, and the hind 

 legs are articulated in a manner which, however firm 

 the soles of the feet were upon the ground, would 

 give the animal very little stability upon them. But 

 they do not even stand firmly, for the tendency of 

 the thumb acting in a cross direction to the other 

 parts of the foot, is to throw the foot on its external 

 edge, a position which is the most tottering of any in 

 the march of an animal. We have a proof of this 

 in human beings, in whose legs there is no very 

 apparent malformation, but who appear merely to 

 have acquired a bad habit of turning in the toes 

 when they walk. In this way, the foot, instead of 

 being planted firmly on the bail of the great toe arid 

 the heel, which are the grand points of support for 

 firm and steady motion, while the outside of the foot 

 is a support against lateral shake, is thrown upon the 

 central portion of the outer edge of the sole for its 

 main support, and the ball or the heel cannot come 

 to bear without a lateral totter. What some of the 

 human race thus acquire, chief! v from bad habit, 

 the apes have by nature, and that to a far greater 

 extent. 



This, however, is not the only disadvantage to 

 which these animals are subjected in walking, in con- 

 sequence of the peculiar articulations of their pos- 

 terior extremities. The pelvis is remarkably narrow, 

 which brings the articulations of the femoral bones 

 verv near to each other : and as the distance between 



NAT. HIST. VOL. III. 



the articulations of these bones is the base which 

 supports the body or trunk of the animal, in the 

 apes, this basal line is much too short for maintaining 

 the body of the animals steady in an erect position. 

 It may appear singular to those who have attended 

 to the statics of dead matter, where there can be no 

 stability but on a basal surface, that the base of an 

 animal should be a line. It is to be recollected, how- 

 ever, that the stability of the animal is not tlte sta- 

 bility of rest, but a stability which must admit of 

 motion ; and this is quite incompatible with a 

 basal surface. It must be remembered too that the 

 line joining the articulations of the femoral or thigh 

 bones, is the base of stability to the trunk, head, and 

 upper extremities only, and this stability in the cross 

 direction, or in the mesial plane of the body, is ob- 

 tained by flexures of the spine, while the stability on 

 the basal line already alluded to, as well as that in 

 the cross direction to this line, are farther secured by 

 the position of the arms ; so that in the motions of 

 the parts above, the animal has really the power of 

 giving this line all the stability of a plane, at the 

 same time that it retains the freedom of it as an axis 

 of motion. We believe this stability in motion is 

 necessarily peculiar to the living structure, and could 

 not be imitated even in the slightest degree by all 

 the complication of mechanical contrivances to which 

 man could resort, and it is thus one of the most beau- 

 tiful instances of the superiority of a power of motion 

 in the moving thing itself, over a power of motion 

 applied to it from without one of the grand dis- 

 tinctions, in short, between an animal and a machine, 

 and a striking proof of the great inferiority of the 

 latter. 



Even this inferior extent and stability of the basal 

 line of the trunk is not the only imperfection which, 

 as an upright animal, an ape sustains in consequence 

 of the principal adaptation of the hind feet being for 

 climbing. The possession of an ox catcis, or heel bone, 

 is perfectly incompatible with the action of a foot. 

 which is to grasp in the same manner as the Coot of 

 an ape does ; and the absence of such a bone is in- 

 compatible with a steady upright position of two feet, 

 as a means of support, and at the same time of mo- 

 tion. In the human subject, the sole of each foot 

 presents a basal line, and consequently the two feet, 

 in which the lines cannot be brought close together, 

 form a basal plane, stable in itself in proportion to 

 the lengths of the lines, and the distance which the 

 feet are apart from each other in a lateral direction, 

 provided they are riot so far apart as to strain the 

 muscles and destroy their free action. The method 

 of walking with the greatest safety upon ice, or any 

 other slippery surface, with the greatest security, is 

 no bad illustration of this. That method is to keep 

 the feet a considerable distance apart, to take short 

 steps, and to hold the joints of the knees and hips, 

 and indeed all the joints, the action of which tends 

 to steady the body in walking, in such a state of 

 relaxation, as that every muscle telling in those joint* 

 may be at perfect freedom to act as necessity may 

 require. 



The two firm basal lines which the human feet 

 affovd, admit of progressive motion by the alternate 

 advance of each ; because the flexures of the bodv 

 and the motions of the arms can be so regulated as 

 to keep the centre of gravity of the entire stnicturo 

 directly over the line which is the base for the time, 

 and while this remains the case, the bodv must be 

 K 



