BIRDS. 341 



externa) in birds is remarkable, it is wider than the brachial 

 artery, which is to be explained by the powerful develop- 

 ment of the great pectoral muscle. In place of one iliac artery 

 on each side from tlie descending- aorta for the hind limbs, two 

 arteries are found in birds, of which the anterior [arteria cruralis s. 

 femoralis) is small and runs above the pelvis under the last rib 

 backwards, whilst the posterior much larger {arteria ischiadica) is 

 the principal artery of the hind limbs, which previously gives off 

 the middle arteries of the kidney. After this the aorta is much 

 diminished in size {art. sacra media). In birds arterial wonder- 

 nets are often present, as a rete mirahile temporale formed by the 

 ophthalmic artery, an external branch of the artery of the brain 

 {arteria carotis interna), a wonder-net at the pecten within the 

 eye-ball, one by the anterior tibial artery, &c.' There are always 

 two superior vence cavoe and one inferior, which return the blood to 

 the right sinus of the heart. The right jugular vein is wider, in 

 some birds much wider than the left, which close to the head is 

 connected with it by a transverse branch and conducts to it a part 

 of the blood ^ 



There are two lungs present in birds, which lie upon the dorsal 

 surface of the cavity of the thorax, attached to the ribs and dorsal 

 vertebrae and not covering the heart; they are not divided into 

 lobes. The two hroncM are, in proportion to the trachea, short; 

 they penetrate the upper part of the lungs on their anterior surface, 

 and are perforated by some large apertures which lead into the 

 wider branches or bronchial tubes of the first order, the extremities 

 of which open on the surface of the lungs and pass into the air- 

 sacs which are in connexion with the lungs. These bronchial 

 tubes again are perforated by smaller apertures which lead into 

 smaller bronchial tubes which anastomose variously with each other 

 so as to form a network of tubes. The walls of these tubes are 



^ On the arterial system of birds compare F. Bauer JDisquisitiones circa nonmiUa- 

 rum avium systema arferiosum, c. fig., Berolini, 1825, 4to; E. Hahn Commentatio de 

 Arteriis anatis, cum tabulis, Hannoverse, 1S30, 4to ; and H. Baekow Anatomische 

 Untersuchimgen uher das Schlagader-system der Vogel, Meckel's, Archiv filr Anatomic 

 und Physiol. 1829, s. 305 — 496, Taf. viii — x. 



2 A figure of the principal veins, with the arteries, in the fowl is to be found in 

 the Catalogue of the Physiol. Series of camp. Anat. contained in the Museum of the 

 College of Surgeons, 11. 1834, PI. 25; the veins of the swan are in part figured by 

 Otto in Carus Tabul. Anat. comp. illustr. vi. Tab. vi. fig. i. 



