480 



THE BESFIBATORY APPARATUS. 



eweep througli a third intercostal 

 vertebra. In their dorsal portion, 



Fi?. 246. 



GENERAL VIEW OF THE AIR EESEEVOIRS OF THE 

 DUCK, OPENED INFERIORLY; ALSO THEIR RELA- 

 TIONS WITH THE PRINCIPAL VISCERA OP THE 

 TRUNK. 



1, 1, Anterior extremity of the cervical reservoirs ; 

 2, Thoracic reservoir ; 3, Anterior diaphragmatic 

 reservoir ; 4, Posterior ditto ; 5, Abdominal reser- 

 voir. — a, Membrane forming the anterior dia- 

 phragmatic reservoir ; b, Membrane forming the 

 posterior ditto. — 6, Section of the thoraco-abdomi- 

 nal diaphragm. — d, Subpectoral prolongation of 

 the thoracic reservoir ; e, Pericardium ; /, /, 

 Liver ; g, Gizzard ; h, Intestines ; m, Heart ; 

 n, -It, Section of the great pectoral muscle above 

 its insertion into the humerus ; o, Anterior 

 clavicle ; p, Posterior clavicle of the right side 

 cut and turned outwards. — From M, Sappey's 

 work. 



sac, it arrives nearer and nearer the last dorsal 

 the prolongations emanating from the cervical 

 reservoirs thus form two currents, 

 though these are constituted alter- 

 nately by the vertebras and the small 

 air-sacs placed on their lateral aspect. 

 At the same time that these sacs 

 receive the air from the vertebrse pre- 

 ceding them, and transmit it to those 

 which follow, they communicate it to 

 all the vertebral ribs. 



" In no order of birds do the serial 

 currents leaving the cervical reser- 

 voirs communicate with those which 

 circulate in the cranium. Liquids 

 injected either by the serial portion 

 of the vertebral canal or the lateral 

 prolongations of the neck, never enter 

 the bones of that cavity. Thinking 

 that the injection might perhaps 

 penetrate if passed in the opposite 

 direction, we have perforated the 

 bones of the cranium, and to the 

 aperture have adapted the extremity 

 of a steel syringe filled with mercury ; 

 but the metal did not reach the serial 

 prolongations of the neck. From this 

 double experiment, we concluded 

 that the cranial bones have no com- 

 munication with the respiratory appa- 

 ratus." 



3. Anterior diaphragmatic reser- 

 voirs (Fig. 246, 3).— "Placed be- 

 tween the two diaphragms, they cor- 

 respond : in front, to the thoracic 

 reservoirs, against which they stand; 

 behind, to the posterior diaphragm- 

 atic reservoirs; outwardly, to the 

 ribs and intercostal muscles ; in- 

 wardly, to the thoraco-abdominal 

 diaphragm and oesophagus ; below, 

 to the most distant part of the tho- 

 racic reservoir; above, to the pul- 

 monary diaphragm, which separates 

 them from the corresponding lung. 

 These air-sacs communicate with the 

 lungs by a circular opening, which 

 originates from the great posterior 

 diaphragmatic bronchus ; there is 

 often a second opening of communi- 

 cation beyond the embouchure of the 

 trunk ; this reservoir is the only one 

 which receives air from the lung by 

 a double orifice." 



4. Posterior diaphragmatic reser- 

 voirs (Fig. 246, 4).—" Oval-shaped 

 like the preceding, and situated like 

 them in the interval which separates 

 the two diaphragms, these air-sacs 

 are in contact, by their anterior part, 

 with the anterior diaphragmatic re- 

 servoirs, with which they form a ver- 

 tical and transverse septum. 



Some- 

 times this septum is carried a little 

 more forward, and then the anterior reservoir is smaller; this is most frequent in 



