MOEPHOLOGY OF THE LIMBS. 



297 



BORDERS 



Axillary border, posterior on '| 1. Lateral 



most animals (attachment of 



triceps muscle) 

 Spine continued into acromion 



Superior border, anterior in 

 most animals, with scapulo- 

 coracoid notch 



2. Antero-medial 



3. Postero-medial 



Anterior border (attachment of rectus 

 muscle) 



Linea arcuata interna continued into 



pubis 

 Posterior border with greater sciatic notch 



Flower's views of this matter were strenuously opposed by Humphry, who maintained that 

 there is strong presumptive evidence against any rotation of the superior parts of the girdles, 

 since it is difficult to suppose that the scapula and ilium can undergo a rotation which is not 

 participated in by the coracoid and ischium. According to this anatomist the homologous parts 

 of the two bones are as stated below : 



Scapula. 



Pre -spinal ridge forming the floor of the pre- 



spinal fossa 

 Spine and acromion 



Post-spinal part of scapula forming the floor of 



the post -spinal fossa 

 Posterior angle 

 Posterior border 

 Medial or ventral surface 



Ilium. 



Linea ilio-pectinea 



Fore part of the blade and crest of the ilium, 



with its anterior spine or angle 

 Hinder part of blade and crest of ilium 



Posterior spine or angle 

 Posterior or sciatic border of ilium 

 Inner or true pelvic surface of ilium, including 

 the surface for the articulation of the sacrum 



B AC 



FIG. 286. DIAGRAM TO ILLUSTRATE THE HOMOLOGOUS PARTS OF THE SCAPULA AND ILIUM, 



ACCORDING TO HUMPHRY. 



A, primitive rod-like ilium of kangaroo, prismatic on section. B, scapula, 



surfaces are similarly coloured. 



C, ilium. The corresponding 



The difficulty arising in this scheme of attempting to homologise the attachments of the 

 triceps and rectus femoris, Humphry explains by pointing out that the former muscle also arises 

 from the lateral surface of the scapula, whilst the rectus overruns the lateral surface of the ilium 

 above the acetabulum, so that there is a correspondence in the origins of both these muscles from 

 the lateral surface of their respective bones ; but in consequence of the rotation of the extensor 

 surfaces of the limbs in opposite directions the triceps has been turned backwards on to the 

 posterior border of the scapula, whilst the rectus has been turned forwards on to the anterior 

 border of the ilium. Sufficient has been said to enable the reader to recognise that all attempts 

 to determine in detail the homologies of these parts are beset with difficulty.. It is wiser, therefore, 

 in our present state of knowledge to be content with establishing a general correspondence, and 

 so avoid the error of endeavouring to establish a closer homological relationship than actually 

 exists. 



In man, since the erection of the figure no longer necessitates the use of the fore limb as a 

 means of support, the shoulder girdle has become modified along lines which enhance its mobility 

 and determine its utility in association with a prehensile limb. Some of its parts remain 

 independent (clavicle and scapula), and are united by diarthrodial joints, whilst others have 



