THE RESPIRATORY APPARATUS IN BIRDS. 481 



Palmipeds. At other times it inclines backwards, and the anterior reservoir is larger ; 

 this arrangement is peculiar to the Gallinacae. And, lastly, this pariition divides the 

 intercepted space between the diaphragms into two equal cavities ; rapacious birds offer 

 numerous examples of this. 



"Behind, these reservoirs stand against the abdominal sacs, from which they are 

 separated by the thoraco-abdominal diaphragm ; below, they respond to the sternal ribs 

 and the lateral parts of the sternum ; above, to the pulmonary diaphragm ; inwards, 

 to the thoraco-abdominal diaphragm ; outwards, to the vertebral ribs and intercostal 

 muscles. 



" A parabolic opening, situated in the middle part of the external border of the lung, 

 or a little more behind, establishes their communication with that organ. This orifice, 

 which is remarkable for its great dimensions, occupies the extremity of a voluminous 

 bronchial tube which follows the direction of the generating trunk, and in such a manner 

 that this trunk appears to pass directly towards the posterior diaphragmatic reservoir, 

 and to open as a canal." 



5. Abdominal reservoirs (Fig. 246, 5). " The two air-sacs situated in the abdomen 

 present themselves, when inflated, as two enormous bladders, the capacity of each 

 differing but little from the volume of the trunk. Situated between the superior 

 and lateral parietes of the abdomen on one side, and the abdominal viscera on tne 

 other, they cannot be dilated without driving the intestinal mass downwards and 

 inwards. 



" Their anterior extremity, continuous with the lung, is somewhat inflected to pass 

 under the fibrous arch extending from the spine to the pelvis. 



" Their posterior extremity, dilated and voluminous, responds to the cloaca. Out- 

 wardly, they adhere by cellular tissue to the thoraco-abdominal diaphragm, the parietes 

 of the abdomen, and those of the pelvis. Inwardly, they are in contact with the intes- 

 tinal mass and the testicles or ovaries. Below and in front, they rest on a fibrous 

 septum, which in all birds divides the abdomiii'l cavity into two smaller cavities: one 

 anterior, which represents the abdomen and lodges the liver, the other posterior, which 

 represents the pelvis and contains the stomach and intestines. This fibrous septum is ex- 

 tremely remarkable in large birds, particularly the Ostrich, in which it has been described 

 by Perrault as a transverse diaphragm; it is insertea into the entire circumference of the 

 pelvic bones, and sustains the stomach as well as the intestinal tube. Below and 

 behind, the abdominal reservoirs lie on the intestines. Above, these sacs cover the 

 inferior face of the kidneys, and there furnish three prolongations : 1, A suprarenal 

 prolongation ; 2, Two femoral prolongations. 



" The suprarenal prolongation leaves the principal reservoir at the postero-external 

 part of the kidneys ; from thence it passes obliquely upwards and forwards, to spread 

 over the superior surface of the kidney, wiiich it depresses when the abdominal sac is 

 inflated. Arrived at the internal border of the kidneys, these prolongations are intro- 

 duced between the transverse processes of the sacral vertebrae, and ascend from behind 

 forwards to the height of the two first dorsal vertebrae, forming two triangular canals 

 situated above the sacrum, in the sacral channels, and separated from one another by a 

 series of corresponding spinous processes. The suprarenal prolongations are not 

 present in all birds ; they are particularly observed in the Gallinacse and diurnal 

 rapacious birds. In some Palmipeds, the Swan for example, they are equally developed ; 

 in the Ostrich, they are replaced by the snpraspinal canals. 



" The femoral prolongations are two in number an anterior small and a posterior 

 large ; they arise from the abdominal reservoir at the cotyloid cavities, and leave the 

 pelvis in traversing the bony opening through which the crural vessels pass ; after clear- 

 ing the limits of these cavities, they spread around the coxo-femoral articulation, and 

 terminate in a caecum in the majority of birds. Iti diurnal birds of prey, they commu- 

 nicate with the femoral canal by an orifice situated at the anterior part of the great 

 trochanter. These prolongations, very developed in the Ostrich, also open in it into the 

 femoral cavity ; it is not without surprise that we see this arrangement, which is peculiar 

 to birds remarkable for their rapidity and power of flight, also present in those to which 

 ferial locomotion has been entirely denied. The abdominal reservoirs communicate with 

 the lung by an orifice situated beneath the fibrous arch of the diaphragm, and disposed 

 like the rose of a watering-can." 



COMMUNICATION OF THE KESERVOIRS WITH THE BONES." The communications of the 

 respiratory apparatus with the skeleton in birds are extremely numerous. Wo will 

 successively examine those belonging to each reservoir. 



_" The bones which receive air from the thoracic reservoir are : 1, The anterior clavicle, 

 which is perforated at its two extremities ; 2, The posterior clavicles, which are also 

 perforated a little below their scapular extremity 3, The sternum which presents two 



