Common Pigeon. 15 



upon the furculum and the muscles arising* from it. In the cavity 

 of the thorax a black bristle has been passed between the proven- 

 triculus and the aorta as this vessel arches over from the left to 

 the rig'ht. The gizzard is concealed from view by the right lobe 

 of the liver and the posterior or xiphisternal end of the sternum 

 which sup])orts and protects both these viscera. The distal segment 

 of the duodenal loop of intestine is held in relation with the under 

 surface of the right lobe of the liver, which is excavated conformably 

 to it. In the concavity of the duodeual fold is seen the longitudi- 

 nally-fissured, compact, elongated, largely-developed pancreas. An- 

 teriorly to this duodenal fold are seen the two other main folds of 

 smaller calibre which the lengthy small intestine of these birds 

 describes. The right side of the heart rests upon the right lobe of 

 the liver ', from which the vena cava inferior is seen to pass up into 

 the right auricle, entering it at a point a little superiorly as well 

 as posteriorly placed to that at which the vena cava superior of the 

 right side opens into it. The veins from the upper extremity 

 and shoulder are cut short at their point of junction with the 

 jugular to form the vena cava superior. The pneumogastric nerve is 

 seen in relation superiorly with the jugular vein ; superiorly again, 

 and internally to the nerve, we see the proventriculus ; and supe- • 

 riorly again to it, the longi colli muscles arising from the vertebral 

 hypapophyses. Tracing the aorta backwards towards the heart from 

 the point where it arched over the right bronchus, which, together 

 with the pulmonary arter}^ placed before it and the pulmonary 

 vein placed behind it, has l^een removed in this dissection, we 

 see it pass behind the vena cava superior dextra, and give off the 

 two arteriae innominatae, one for either side of the body, very close 

 to the base of the heart. The right arteria innominata is seen to 

 divide into its common carotid and subclavian trunks. This latter 

 vessel, after giving off a small Ijranch homologous with the in- 

 ternal mammary artery of anthropotomy, divides into an axillary 

 trunk, which passes into the wing together with the brachial 

 neiwes, and into the much larger arteria thoracica externa which 

 supplies the great pectoral muscles. The lung, which occupies a 

 much smaller space in the dorso-sternal plane than in mammals, 



' For the jteculiarities of the circulatory system, see Cuvier and Duvernoy, 1. c. 

 torn. vi. p. 192; Barkow, 'Meckel's Archiv,' 1829, p. 493; and for a figure of the 

 circulatory system, ' Hunterian Catalogue,' Phys. Series, vol. ii. pi. xxv. 



