430 



NATURE 



[September 2, 1897 



is wider and extends higher on the front of the bone than the 

 inner part, whilst the direction of the curve changes towards the 

 edges of the trochlea. 



In the apes the articular surface of the inner condyle is very 

 markedly larger than that of the outer condyle, both in breadth 

 and in the extent of its backward curve, which winds upwards on 

 the posterior part of the condyle, so that the articular surface is 

 continued on to its upper aspect. The curve of the outer con- 

 dyle is much sharper, and the condyle does not project so far 

 backwards ; its articular surface is not prolonged so high on the 

 back of the bone. In the apes, therefore, the inner is the more 

 important condyle in the construction of the knee joint, and the 

 marked extension of its articular area backwards and upwards 

 is associated with the position and movements of the knee in 

 flexion. In the ape the thigh is more rotated outwards than 

 in man, and the inner condyle is directed to the front of the 

 limb. 



In man there is not nearly the same disproportion in the size 

 of the two condyles as in the apes. I have occasionally seen 

 in man the articular area of the inner broader than that of the 

 outer condyle, but more usually the outer is appreciably wider. 

 The backward curve of the outer condyle is also prolonged some- 

 what higher than that of the inner, and thus the condition of 

 the two condyles is the reverse of that found in the ape. It 

 should, however, be stated, as has been shown by Dr. Havelock 

 Charles {Journal of Anatomy and Physiology, vol. xxviii. ), 

 that in persons, who habitually rest in the squatting position, an 

 upward extension of the articular area of the inner condyle exists, 

 which is associated with the acute flexion of the knee whilst 

 squatting. In man, the outer condyle, when seen in profile, is, 

 as compared with the inner, more elongated antero-posteriorly 

 tlian in the Gorilla. The approximate equality in the size of the 

 two condyles in man is, without doubt, associated with the 

 extension of the knee joint in the erect attitude, and with the 

 more equable distribution of the weight of the body downwards 

 on the head of the tibia. In the ape the intercondylar fossa, in 

 relation to the size of the bones, is wider in front than in man ; 

 but it is wider behind in man than in the ape, for in the latter 

 the inner condyle inclines nearer to the outer condyle than 

 in man. 



In man, when the knee joint is extended, the tibia is slightly 

 rotated outwards on the femoral condyles, and the joint is fixed, 

 partly by the tension of the lateral and posterior ligaments and 

 the interior crucial ligament, and partly by the general tension of 

 the muscles and fasciae around the joint. So long as these 

 structures remain tense, the joint cannot be bent, and no lateral 

 movement, or rotation, is permitted. The fixation of the joint 

 is of fundamental importance in the act of standing. Free rota- 

 tion of the human knee can only take place when the joint is 

 acutely bent. 



In apes, the joint cannot be fully extended ; its natural posi- 

 tion, when the animal is standing, is partial flexion, and in this 

 position a limited rotation is permitted, which can be greatly 

 increased when the joint is more completely bent. In rotating 

 the leg on the thigh the inner condyle is apparently the pivot. 

 The rotation facilitates the use of the foot as an organ of prehen- 

 sion, and assists the ape to turn the sole inwards and forwards 

 when holding an object. These movements produce results, 

 which approximate to those occasioned by pronation and supina- 

 tion of the radius on the ulna, in the movements of the forearm 

 and hand. 



In the Anthropoid apes, the head of the tibia slopes very 

 decidedly backwards at the upper end of the shaft, so that its 

 axis forms an angle with that of the shaft, and the head may be 

 described as retroverted. If the shaft of the tibia were held 

 vertically, the articular surface for the inner condyle would also 

 slope downwards and backwards, and to a greater degree than 

 that for the outer condyle. But in the natural semiflexed position 

 of the ape's knee the condylar articular surfaces of the tibia are 

 essentially in the horizontal plane. 



In the human tibia the axis of the head is, as a rule, almost in 

 line with that of the shaft, and the backward and downward 

 slope of the inner articular surface is not so great as in the ape. 

 In some human tibiae, however, well-marked retroversion of the 

 head has been seen. In skeletons referred to the Quaternary 

 period of the geologist, this character has been noticed by MM. 

 Collignon, Fraipont, and Testut, and the inference has been 

 drawn that the men of that period could not extend the knee 

 joint and walk as erect as modern man. It has, however, been 

 shown by Prof. Manouvrier {Mimoires de la Societe d'Anihro- 



NO. 1453, VOL. 56] 



pologie de Paris, 1890) and Dr. Havelock Charles {Journal oj 

 Anatomy and Physiology, vol. xxviii.) that this condition of the 

 tibia is not uncommon in some races of men, in whom there 

 can be no question that the attitude is erect when standing. 

 Dr. Charles has associated the production of retroversion to the 

 habit in these races of resting on the ground in the position of 

 squatting. I have found in the tibiae of the people of the 

 Bronze Age that retroversion of the head of the tibia is not un- 

 common. In five specimens the backward slope of the head 

 formed with the vertical axis of the shaft an angle which ranged 

 in the several bones from 20° to 30°. But when these tibiae were 

 put into the erect position alongside of similarly placed modern 

 European bones, the condylar articular surfaces were seen to 

 approximate to the horizontal plane in all the specimens. la 

 order, therefore, that retroversion of the head of the tibia 

 should be associated with inability to extend the knee joint, it 

 is obvious that the articular surfaces should have a marked slope 

 downwards and backwards, as is the case in the Anthropoid 

 apes, when the shaft of the tibia is held in a vertical plane. 



I shall now proceed to the examination of the human foot 

 (pes), and in order to bring out more clearly its primary use as 

 an organ of support and progression, I shall contrast it with the 

 human hand (manus) and with the manus and pes in apes. In 

 man, while standing erect, the arched sole of the foot is 

 directed to the ground, and rests behind on the heel and in 

 front on pads, placed below and in line with the metatarso- 

 phalangeal joints, the most important of which is below the 

 joint associated with the great toe. It is therefore a plantigrade 

 foot. The great toe (hallux) lies parallel to the other toes, and 

 from its size and restricted movements gives stability to the 

 foot. 



The ape's foot agrees with that of man in possessing similap 

 bones and almost similar soft parts ; but it differs materially as 

 to the uses to which it can be put. Some apes can undoubtedly 

 place the sole upon the ground, and in this position use the foot 

 both for support and progression ; though the Orang, and to 

 some extent other Anthropoid apes, rest frequently upon the 

 outer edge of the foot. But in addition these animals can use 

 the foot as a prehensile organ like the hand. The old anatomist 

 Tyson, in his description of a young Chimpanzee (" Anatomy of 

 a Pygmie," 1699, p. 13), spoke of the pes as " liker a hand than 

 a foot" and introduced the term " quadrumanous," four- 

 handed, to designate this character. This term was adopted by 

 Cuvier and applied by him to apes generally, and has long been 

 in popular use. The eminent French anatomist was, however, 

 quite alive to the fact that though the pes was capable of being 

 used as a hand, yet that it was morphologically a foot, so that 

 the term was employed by him to express a physiological 

 character. 



In the ape, the great toe, instead of being parallel to the 

 other toes as in man, is set as an angle to them, not unlike the 

 relation which the thumb (pollex) bears to the fingers in the 

 human hand. It is able, therefore, to throw the hallux across 

 the surface of the sole in the prehensile movement of opposition. 

 As it can at the same time bend the other toes towards the sole, 

 it also has the power of encircling an object more or less com- 

 pletely with them. By the joint action of all the toes a power- 

 ful grasping organ is produced, more important even than its 

 hand, in which the thumb is feebly developed. 



It has sometimes been assumed that the human foot is also a 

 prehensile instrument as well as an organ of support. In a 

 limited sense objects can undoubtedly be grasped by the 

 human toes when bent towards the sole. In savages, this power 

 is preserved to an extent which is not possible in civilis'ed man, 

 in whom, owing to the cramping, and only too frequently the 

 distorting influence, exercised by badly fitting boots and shoes, 

 the proper development of the functional uses of the toes is im- 

 peded and their power of independent movement is often de- 

 stroyed. 



Even in savages who have never worn shoes, the power of 

 grasping objects by the toes cannot be regarded as approximately 

 equal in functional activity and usefulness to the range of move- 

 ment possessed by the ape. The four outer toes are so short 

 and comparatively feeble, that they cannot encircle an object of 

 any magnitude. But, what is even more important, the great 

 toe cannot be opposed to the surface of the sole, in the way 

 that an ape can move its hallux or a man his thumb. Savage 

 man can no doubt pick up an object from the ground with the 

 great toe. Many of us have doubtless seen, among civilised 

 men, persons who have had the misfortune to be born without 



