COMPARISON OF SHOULDER AXD PELVIC GIRDLES. 123 



Homological Comparison of Upper and Iiower Limbs. — A certain 

 anatomical correspondence between the upper and lower limbs, which is apparent 

 to common observation, is admitted in even a fuller degree by most scientific 

 anatomists as the result of a careful comparison of the form, structui-e. and 

 relations of their bones, as well as of their other parts. But very different views 

 have been taken of the nature and extent of the comparison which may be made 

 between them. Thus Vicq d'Azyr compared the bones of the upper limb of one 

 side of the body to the bones of the lower limb of the other ; and Bourgery and 

 Cruveilhier regarded the upper end of the tibia as homologous with that of the 

 ulna, while they compai-e its lower end to that of the radius. But all such 

 fanciful views have now yielded to the fuller appreciation of homological 

 correspondence which has resulted from a more careful comparison of structure 

 in a wide series of animals, and the study of their transformations in embryonic 

 development ; and thus the general conclusion has been fonned, that the thoracic 

 and pelvic limbs are constructed on the same general type in man and animals, 

 both as regards the attaching gii-dles of the shoulder and jjelvis. and in the 

 three several sections of which each limb is composed. There are. however, 

 certain modifications of that general plan, leading to considerable differences in 

 the form, size, and number of the individual parts in different animals, which 

 appear to be in a great measure related to the different uses to which the upper 

 and lower limbs are respectively applied ; as, for examjale, in the upper limb of 

 man, the breadth of the shoulders, caused by the inteiToosition of the clavicle, 

 the gi'eater extent of mo tion in the shoulder joint, the eversion of the humerus, 

 and the forward flexed attitude of the elbow-joint, the arrangements for pro- 

 nation and supination by rotation of the radius and hand, and the opposability 

 of the thumb, all have reference to the freedom, versatility, and precision 

 of the movements of the upper limb as an organ of prehension and touch ; while 

 in the lower limb, the comparatively iixed condition and arched foiTn of the 

 pelvic girdle, the gi-eater strength of the bones, the close-fitting of the hip-joint, 

 the inversion of the femui', the backward flexure of the knee-joint, the arched 

 form of the foot, and non-opposability of the gi^eat toe. have all manifest relation 

 to the support of the trunk and pelvis, and theii" movements upon the lower 

 limbs. In the lower animals, gi'eater modifications in the form of both limbs are 

 to be observed, obviously adapted to their different functions in each case. 



Without attemiitiug to follow out this subject by any detailed reference to 

 comparative anatomy or development, it may be useful to state here shortly the 

 more probable conclusions which have been formed by the most recent inquii-ers 

 with respect to the homological correspondence of the several parts of the upper 

 and lower limbs.* 



Shoulder and Pelvic Girdles. With res^iect to the attaching bones of the 

 two limbs, it is generally held that the blade of the scapula coiTcsponds with the 

 ilium, each of them fonnuig the dorsal section of their respective arches : and 

 the gi'eatest difference between them consisting in the scapula being entii-ely free 

 from bony articulation with the vertebral column, and capable therefore of 

 considerable motion, while the ilium is firmly jointed to the lateral mass of the 

 sacmm. The ventral part of the shoulder-gii-dle, completed by the articulation 

 of the clavicles with the sternum, presents no doubt at first sight some similarity 

 to the meeting of the ossa jiubis at the symphysis : and thus at one time the 

 clavicle and the pubis were looked upon as homologous bones. But the fuller 

 knowledge of comparative anatomy has more recently led to the adoption of a 

 different view, according to which it appears more probable that the pubis repre- 

 sents rather the epicoracoid bone of the Monotremata and of Reptiles, while, as 

 before believed, the coracoid process of man, originally separate, and typically ai 

 distinct bone, is represented in the pelvic girdle by the ischium. Thus. then, it 

 appears that the clavicle is not repeated in the lower limb girdle ; and in the 

 place of the very imperfect coracoid process of man and most mammals, there 



* It is right to mention that, while in the comparison here given most British and 

 European authors coincide, opinions widely different from these are held by several com- 

 parative anatomists of distinction in America, among whom may be mentioned Agassiz, 

 Wyman, Wiidei-, and Coues. 



