THE RESPIRATORY APPARATUS IN BIRDS. 557 



CHAPTEE II. 



The Respiratory Apparatus in Birds. 



The organs composing- the respiratory apparatus of Birds offer conditions alto- 

 gether special, which have a remarkable influence on the mechanism of respira- 

 tion. The modifications in the performance of this function will be indicated 

 after an examination of the tubular apparatus which carries air into the Iwiff, 

 and the characters of that organ, as well as the air-reservoirs (or sacs) annexed 

 to it. 



The Tubular Apparatus which carries Air to the Lungs.— When 

 this apparatus is compared with that of Mammals, no very sensible differences are 

 observed— at least, in domesticated Birds. 



The nostrils, pierced through the upper mandible of the beak, have no mem- 

 branous and movable alse, and the nasal fossae open into the pharynx by a long, 

 narrow slit behind the bony palate. A transverse row of small, horny papillae, 

 placed at the anterior extremity of this aperture, represents the soft palate. 



The larynx has no epiglottis : a defect which does not prevent the complete 

 occlusion of the glottis during the passage of food, as the laryngeal orifice is 

 circumscribed by two lateral lips, which then meet in the most exact manner. 



The trachea is composed of complete cartilaginous rings, and not simple arcs. 

 In Song-birds, the last ring is a second larynx, the real organ which produces the 

 modulated voice of these creatures ; it only exists in a rudimentary condition in 

 Poultry, however, the last tracheal piece in them being slightly dilated, and 

 showing at the origin of the bronchi a membranous layer, from whose vibration 

 results cries or crowing. Other singular peculiarities belonging to the trachea 

 deserve to be described here, if they were not the exclusive appanage of some wild 

 fowl. "We are content to mention the presence of the bony drum found at the 

 terminal extremity of the trachea in the whistling Duck, and the remarkable con- 

 volutions that tube forms in the breast-bone of Cranes and male Swans. 



The hrofichi only show incomplete rings in their structure. They pass into 

 the lung by its inferior face, towards the union of its anterior and two posterior 

 thirds. When describing this organ, their mode of ramification, and the nature 

 of the relations they bear to its proper tissue, will be considered. 



The Lungs. — Sappey, in the remarkable memoir published by him in 

 1847,^ has described them as follows : " The lungs of Birds are situated on the 

 lateral parts of the vertebrse of the back — which separate them, and lying 

 against the arch of the thoracic cavity, to which they adhere. Their rosy colour 

 resembles that presented by these organs in Man and the Mammalia during 

 uterine life, and for some time after birth ; they are especially remarkable for 

 their restricted volume, which scarcely represents an eighth part of the thoracic 

 capacity. Their configuration is far removed from the conical form of the lungs 

 in Mammals, and the oval form of the same organs in reptiles ; they are semi- 

 elhptical, and if the two lungs of a Mammal were opposed base to base, their 

 hkeness would be produced : to obtain the same results with the limgs of a 

 reptile, it is necessary to divide them in the direction of their great axis. 



" This shape enables us to distinguish in the lungs of a bird, two faces — a 

 ' Sappey, Becherches sur I'Appareil Respiratoire des Oiseaux. Paris : 1857 

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