16 PRACTICAL ORNITHOLOGY. 



side of the spine. This fascia, which is analogous to the dia- 

 phragm of the MammaHa, generally has on each side three 

 muscular slips attached to three of the hinder ribs. The ac- 

 tion of these muscles, being to render the fascia tense, must 

 dilate the lungs and thus be subservient to inspiration, although 

 the extent of the vacuity formed by them is slight compared 

 with that produced by a regular diaphragm. The lungs them- 

 selves are not, properly speaking, invested by the pleura, but 

 are covered by a very delicate membrane, which becoming cel- 

 lular above, attaches their whole upper surface to the parietes 

 of the thorax. The bronchi, or divisions of the windpipe enter 

 upon their anterior surface, and at length divide into several 

 branches, which communicate by openings on their upper or 

 posterior surface with the air-cells of the lungs, and terminate 

 by wide apertures in the large cells or receptacles of air distri- 

 buted in the thorax and abdomen. The pulmonary artery, 

 which carries the venous or dark blood to the lungs, to be pu- 

 rified, divides immediately after its commencement, into two 

 branches, one going to the right, the other to the left lung, and 

 its ultimate twisfs anastomose on the air-cells with those of the 

 pulmonary veins, which in like manner unite into two great 

 branches, and these finally into a single trunk. 



The cells, with which the bronchi communicate after passing 

 through the lungs, vary in form and number in different birds. 

 One of them, named the interclavicular, extends from the fore 

 part of the lungs to the space between the crura of the furcula, 

 and is generally of very large size. The anterior thoracic con- 

 tains the bifurcation of the trachea, the bronchi, and the great 

 vessels entering or issuing from the heart. It is traversed by 

 numerous membranous dissepiments, and communicates with 

 the air-cells that extend up the sides of the neck. The lateral 

 thoracic cells occupy the sides of the thorax, and commu- 

 nicate with a series of cells surrounding the heart, and inter- 

 posed between it and the sternum, as well as with others 

 in the axilla, which are continuous with cellules occupy- 

 ing the sides of the body, part of the wing, and the cavity 

 of the humeral bone. Two large cells, which have been 

 named the hepatic, extend from the lower surface of the 



