CONNECTED WITH THE SHOULDER- JOINT. 125 



front of the glenoid cavity, and with a second which joins the first 

 on its mesial border, as it passes round from the internal surface 

 of the scapula, and is inserted into the outer tuberosity of the 

 humerus, in close connexion with the upper edge of the great 

 pectoral. In the descriptions given of this muscle, both in the 

 crocodile and in the Ornithorhynchns, it has been confounded with 

 the deltoid. It is, however, shown by its innervation to be separate 

 from it in nature ; and its insertion lies between the insertions of the 

 deltoid externally and that of the pectoralis major internally. This 

 muscle has a single tendon in the sparrow-hawk, with three 

 muscular heads converging upon it. In the Gallinaceous birds 

 (Gallus gallinaceus and Phasianm colchicus) the levator-humeri 

 apparatus consists of three muscles, distinct both in origin and 

 insertion, and innervated from two distinct sources. The largest 

 of the three levator muscles of the Gallinaceous humerus has a very 

 extensive origin from the sternum; but, as is the case in the 

 pigeon also, it has no distinct accession of fibres from the eoracoid ; 

 but from the eoracoid on its inner aspect, from the coraeo-clavicular 

 membrane, and from a small portion of the sternum a lesser levator 

 humeri arises, which is inserted, after passing through the coraco- 

 scapular canal and over the eoracoid pulley, together with the 

 tendon of the greater levator, between the point of insertion of this 

 muscle (which is a little lower down, and more externally placed) 

 and that of the great pectoral to its inner side. With the tendon 

 of the greater pectoral depressor that of the lessor levator is very 

 closely connected, as is that of the epicoraco-humeral of the croco- 

 dile ; and it is only the presence of the pulley arrangement which 

 converts cooperation into antagonism. 



Thirdly, the small muscle which has been described as passing to 

 the single levator tendon of the sparrow-hawk from the mesoscapula 

 of that bird, has in the Gallinae a larger size, a more extensive origin, 

 and a separate insertion. It arises from the uppermost and inner- 

 most scrap of the scapula, i. e. from the ' mesoscapula ' of Parker, from 

 the ligament which passes along the inner aspect of the coracosea- 

 pular canal from the mesoscapula to the eoracoid, and from the inner- 

 most and uppermost scrap of the eoracoid itself. Its tendon is in- 

 serted externally to that of the smaller levator humeri, internally 

 and proximally to that of the great levator. In the common goose 

 this muscle, the 'deltoides externus' of Meckel, is fused with a 



