THE SKELETON ADAPTED TO THE ERECT POSTURE. 117 



that the upper and lower limbs ought to be regarded not as lying in series but as 

 facing one another, that is to say, as being related to one another symmetrically, 

 one at the upper and the other at the lower end of the trunk, in the same way that 

 the limbs of the opposite sides are arranged symmetrically on each side of the mesial 

 plane. Thus, in the skeleton of a quadruped, the scapula and humerus slope back- 

 wards from the shoulder-joint, and the ilium and femur slope forwards from the hip- 

 joint; the prominence of the elbow looks backwards, and that of the knee looks 

 forwards ; and hence, according to Humphry, the coracoid and pubis and the clavicle 

 and ischium respectively correspond. It will, however, suggest itself to the reader 

 from the remarks already made, that there are serious difficulties in the way of 

 attributing to those appearances, which are only the result of later development, 

 more than a mere secondary importance. (Copious reference to the literature of this 

 subject is made in the paper by Ch. Martins in the " Annales des Sciences Naturelles, 

 Zoologie," vol. viii. 1857, p. 45. See also Humphry, " On the Limbs of Vertebrate 

 Animals," &c. Cambridge, 1860.) 



RELATION OP THE LIMBS TO THE SEGMENTS OF THE TRUNK. 



The various anatomists who have written on this subject agree in considering that 

 the limbs, in their extent beyond the shoulder and hip, are radiations from or appen- 

 dages of one or more segments of the trunk. Opinions, however, are much divided 

 with regard to the nature of the pelvic and shoulder girdles, and, in particular, it 

 has been warmly debated whether or not they are costal arches. Owen hoids the 

 opinion that they are costal, and further considers that the scapula and coracoid process 

 form the costal arch of the occipital vertebra, with the free part of the limb as its 

 appendage, while the clavicle is derived from another segment ; and that in like 

 manner the ilium and ischium form the costal arch of one segment supporting the 

 lower limb, and that the pubic bone belongs to another. The circumstance which has 

 specially led to the supposition that the upper limb and the occipital bone are con- 

 nected is, that the shoulder girdle is attached to the skull in most osseous fishes ; but 

 it may be objected to this hypothesis that in the higher vertebrata the anterior 

 extremities are developed from a portion of the embyro considerably removed from 

 the skull ; and Goodsir fairly argues, from the nervous supply to the limbs, and from 

 the limbs first appearing with the digits arranged in series in the plane of the lateral 

 plates of the embryo, that a limb is not an appendage to a single segment of the 

 trunk, but belongs to several segments. (Owen, " On the Nature of Limbs ; " 

 Goodsir, " On the Morphological Constitution of Limbs," Edinb. New. Phil. Journ., 

 Jan., 1857.) 



THE SKELETON ADAPTED TO THE ERECT POSTURE. 



Throughout the whole of the human frame numerous peculiarities in the form and 

 proportion of parts exists, connected with the assumption of the erect posture. The 

 most striking of the structural peculiarities related to this circumstance are seen in 

 the skeleton, and they are equally apparent in the head, trunk, and limbs. The body 

 of man, unlike that of animals, is, for the purposes of station and progression, balanced 

 on one or both pelvic limbs, which are extended to a straight line at the knee-joint. 

 The lower limb is remarkable for its length and strength. The foot of man alone has an 

 arched instep, and it likewise presents a great breadth of sole. The great toe is distin- 

 guished by its large development, and, especially from that of the quadrumana, by its 

 want of opposability, being formed not for grasping but for supporting the weight of 

 the body and giving spring to the step. The femur is greatly elongated, its length 

 exceeding considerably that of the tibia. This length of femur is not only requisite 

 in order to give a sufficient extent of stride, but also to enable the body to be 

 balanced in different degrees and varieties of stooping. Thus, for example, in a 

 crouching attitude, with the feet placed side by side, it is necessary in order to 

 balance the fore part of the body that the pelvis should be brought back behind the 

 perpendicular rising from the balls of the toes on which the weight is rested : and 

 in order to accomplish this, if there be a long tibia directed forwards from the ankle, 

 there must be a femur of still greater length directed backwards from the knee. The 

 breadth of the pelvis, in like manner, in lateral movements of the body, enables the 

 balance to be more easily maintained by compensating inclinations of different parts to 



