Common Pigeon. 13 



The surface of the cerebral o voids is smooth g ; the proportion 

 of the encephalic nervous mass to the intraspinal is much greater 

 than in the cold-blooded vertebrata. The backward projection 

 of the cerebellum is very considerable. The eyes are large. The 

 vertical third eyelid is drawn forward. The nostrils open externally 

 as long slits overhung by a tumid membrane ; the external audi- 

 tory meatus, which has no concha, has the feathers arranged round 

 it like a circlet of tentacles. The great pectoral h muscle, the 

 main depressor of the humerus and the wing, is seen in section 

 along its origin from the lower portion of the keel of the sternum, 

 and from the furculum, the outer and lateral portions of the sternum, 

 from which it also took origin, having been removed. Placed dor- 

 sally with reference to this muscle we see the second pectoral, the 

 main elevator of the humerus and the wing, arising from a larger 

 portion both of the keel and of the lateral parts of the sternum than 

 the pectoralis major, and passing internally to the coracoid to enter 

 its pulley-like canal, formed by the clavicle or furculum, the cora- 

 coid, and the scapula. 



From this canal, its tendon, which is cut short, is seen issuing on the 

 further side of the glenoid socket for the head of the humerus. The 

 cut-shoi"t triangular end of the pectoralis major is seen to become 

 partially bifid towards its apex ; in the perfect condition of the parts 

 the smaller inferiorly-placed division of the muscle gave off two tendons, 

 one to the long and the other to the short extensor plicae alaris an- 

 terioris ; the larger division passed over a smooth facet on the humei'us 

 and over the coracoid head of the biceps to be inserted into the gi'eat 

 triangular tuberosity of the humerus. Dorsally to the apex of the great 

 pectoral we see a thin stratum of muscle in relation internally with 

 the crop and homologous Avitli the deltoid of anthropotomy. This muscle 

 was divided into three portions, of which the first and most internally- 

 placed joined the long extensor of the anterior fold of alar membrane ; 

 the second and mesially-placed portion joined the short extensor, whilst 

 the third was inserted into the outer aspect of the humerus from its 



e For the nervous system of birds, see C. G. Carus, 'T.abulac Anat. Comp. Illus.' 

 pars vii. tab. v. fig. 7. 



h For the muscular system generally, see Cuvier, * Lecons d' Anatomic Comparee,' 

 vol. i. For the muscles of the wing and shoulder, see Schoepss's Monograph in 

 'Meckel's Archiv,' 1829, and plate ii. with description in this work. For those of the 

 lower extremity, see Professor Haughton, ' Proceedings Royal Irisli Academy,' 

 May 23, 1864 ; Professor Owen, 'Comp. Anat.' vol. ii. p. 107. 



