APPENDIX. 453 



cular attachments. The homology of these two muscular masses 

 affords a key, not only to the general muscular homologies of the 

 arm and thigh, hut also to the corresponding osseous homologies. 



The iliacus internus and psoas magnus are attached together 

 into the trochanter minor. Of these two muscles the iliacus 

 internus has been hitherto considered by the few anatomists who 

 have directed their attention to this subject, as the homologue of 

 the subscapularis ; but it has never apparently been taken into 

 consideration, that whereas the subscapularis passes from the 

 scapula to the humerus, under and behind both the clavicle and the 

 coracoid, the iliacus internus and psoas magnus pass from the ilium 

 to the femur in front of and above the pubis and ischium, the 

 homologues of the clavicle and coracoid. 



The iliacus internus cannot therefore be the homologue of the 

 subscapularis. It will be observed, that if the brachialis anticus 

 were to mount upwards, on the front of the humerus, to the region 

 of its tuberosities, and to force its margins backwards until they 

 nearly met on the back of the shaft of the bone, it would force the 

 humeral attachment of the deltoid upwards and inwards, so that it 

 Avould assume a position on the humerus corresponding to that of 

 the trochanter minor and the thigh-bone. The outer surface of the 

 ilium gives attachment to a pair of muscles — the gluteus medius 

 and minimus — which are the homologues of the inferior spinatus 

 and teres minor muscles ; the internal surface gives attachment below 

 to the obturator internus, which is the homologue of the subscapu- 

 laris ; the anterior surface, which gives attachment to the iliacus 

 internus, must therefore correspond to that portion of the scapula 

 intermediate between the subscapular fossa and the inferior spi- 

 natus at the cervical margin of the bone. The muscle, therefore, 

 arising from the surface, must be either the homologue of the supra- 

 spinatus muscles, or the scapular portion of the deltoid. 



But as the supra-spinatus muscle is attached along with the 

 Lnfra-spinatus and teres minor to the trochanter major while the 

 scapular portion of the deltoid is attached to the deltoid surface, 

 which again is continuous with the great tuberosity by the anterior 

 margin of the bicepital groove ; and as we have already seen that 

 llii- deltoid surface would be forced upwards and inwards, and 

 backwards, into the position of the Lesser trochanter of the femur, 



