CONNECTED WITH THE SHOULDER-JODsT. 129 



deltoid. Yet, as is seen by fig. 3, this muscle receives a head from 

 a surface of the scapula as completely turned viscerad as the iliacal 

 surface of the ilium ever is. The origin of the slender epicoraco- 

 humeral of the chamaeleon is limited to the external surface of its 

 coracoid and praecoracoid ; but its supraspinatus, if we may so style 

 the muscle which comes next in order from below upwards after the 

 deltoid, does receive just such a factor from the visceral surface of 

 the scapula as does the epicoraco-humeral of the crocodile. This 

 muscular belly having the stem of the scapula placed exteriorly 

 to it reminds one forcibly of the relation held by the os ilii to the 

 iliacus ; but the lesson which it teaches does not depend upon such 

 resemblances as this, but upon the retention to some extent by the 

 chamaeleon of the primitive rod-like character of the scapula, which 

 makes it easier for us to see how it may rotate any one of its 

 surfaces, when developed like the fluting on a column, into several 

 different bearings in different animals. It is easier for us to un- 

 derstand how a muscle can wrap its origin round and about the 

 various aspects of a cylindriform, than it is for us to conceive of 

 similar indifferentism in the various surfaces of a many-facetted 

 bone ; and upon the conquering of this difficulty depends our 

 power of homologising the spinati with the iliacus 1 . 



A second argument in the same direction presents itself from 

 another quarter, that of innervation. The homologies of the nerves 

 of the two limbs are much masked by the iliopsoas having carried 

 with it in front of the pubic arch the anterior crural nerve — as 

 also by the separation from this nerve of the peroneal trunk, which 

 is seen, by its distribution, to correspond mainly with those elements 

 of the musculo-spiral nerve which are distributed in the distal seg- 

 ments of the upper limb. But if we place side by side, with 

 diagrams of the nerves of the two limbs, such as those given in 

 plates iii. and iv. of Mr. Flower's ' Diagrams,' tables which give 

 the spinal nerves to which the nerves of the limbs are ultimately 

 traceable, we see that the suprascapular nerves correspond with the 

 nerves to the iliacus, and the nerve to the subclavius with the branch 



1 The so-called ' third or deep head ' of the Iliopsoas (see Henle, ' Handbuch Anat. 

 Mensch.' i. 3. 242), the musculus iliacus interims minor of Luschka ('Anat. Mensch. 

 ii. 2. 131) is described by the latter anatomist as lying quite exteriorly to the pelvic 

 cavity. It comes thus to correspond most instructively with a teres minor. Similarly 

 helpful is the large size of the facet of origin of the teres major in such an animal as 

 Urn us maritimus. 



K 



