840 



AVES. 



the fore-arm, just below the articulation in 

 company with the nerve, and running along 

 the inferior edge of the ulna, receives a branch 

 from between the basis of each quill, is con- 

 tinued along the ligament which sustains the 

 rest of the quills to the extremity of the wing, 

 receiving many veins of the joints from the 

 opposite side of the ringers. Besides these 

 large superficial veins of the fore-arm, there 

 appears to be one, and sometimes two, small 

 accompanying veins to the ulnar and interos- 

 seous arteries (y). 



" The inferior vena cava (K), before it enters 

 the auricle (A), receives as usual the hepatic 

 veins (s) ; these are numerous, and open into 

 the cava as it passes behind the liver, or more 

 frequently within the substance of that viscus 

 in the back part. We have reckoned in the 

 Cock two large and two small hepatic veins 

 from the right lobe, and one large branch from 

 the left lobe, besides six minute veins, which 

 came indifferently from both lobes. 



" The trunk of the vena cava is very short 

 in the abdomen; it separates into two great 

 branches analogous to the primary iliac veins (), 

 opposite to the renal capsules ; these turn to 

 each side, and experience a very singular dis- 

 tribution. On coming near the edge of the 

 pelvis each of these two veins forms two 

 branches ; one of which collects the blood of 

 the lower extremity, as hereafter described; the 

 other passes straight downwards imbedded in 

 the substance of the kidney, and admits the 

 several emulgent veins, which are very large, 

 and are seen to pass for some way obliquely 

 in the kidney before their termination. Some- 

 times the emulgent veins are double, as in the 

 figure, (M). The descending branch of the iliac 

 also receives the ovarian veins, and when arrived 

 at the lower end of the kidney, divides into three 

 branches; one transmits the blood of the muscles 

 of the tail and parts adjacent ; another accom- 

 panies the ureter to the side of the rectum, and 

 is distributed about the anus and parts of gene- 

 ration, answering to the htemorrhoidul veins ; 

 the third (v, v) passes inwards to the middle line 

 between the kidneys, and there unites with the 

 corresponding branch of the opposite side.* 

 The vessel which is in this manner produced 

 (*) receives all the blood of the rectum from the 

 anus to the origin of the cceca, anastomosing 

 below with the branches of the hsemorrhoidal 

 veins ; and at the upper part of the rectum, 

 it becomes continuous with the trunk of the 

 veins of the small intestines (.reforming the most 

 remarkable anastomosis in the body, both on 

 account of its consequences and the size of the 

 vessels by which it is effected. By means of* 

 this communication, the blood of the viscera 

 and the external parts of the body flows al- 

 most indifferently into the vena cava and vena 

 portae (iv) ; for the anastomosing vessels are suf- 

 ficiently large to admit the ready passage of a 

 considerable column of blood in proportion to 

 the whole mass which circulates in the body 



* It is these branches which Professor Jacobson 

 supposes to carry venous blood into the kidneys, 

 for the purpose of supplying material for the uri- 

 nary secretion. 



of the bird ; for instance, in the Goose the com- 

 municating veins of the pelvis are equal in 

 size to a goose-quill, and in the Ostrich and 

 Cassowary they are as thick as a finger. The 

 advantage which appears to result from this 

 remarkable union of vessels, is the prevention 

 of congestion, or the overloading either the 

 heart or liver with blood, as the one organ has 

 the power of relieving the other. It would 

 seem from this, as well as several other pro- 

 visions of the same kind, that the circulation 

 would be more liable to obstruction in birds 

 than other animals.* It is difficult to say, how- 

 ever, to what cause such an effect ought to be 

 ascribed. Is it from the compression sus- 

 tained by the heart and other viscera, by 

 means of the air-cells during respiration ? or, 

 is the mode of progression by flight capable of 

 impeding the motion of the blood ? 



" The anastomosis of the pelvic veins, in 

 being the means of conveying common venous 

 blood into the liver, goes to prove that the 

 blood of the vena portae does not require any 

 peculiar preparation by circulation in the spleen 

 or other viscera, which has been conceived as 

 necessary by some physiologists to fit it for the 

 secretion of bile. 



" The vena portce (w) belongs almost exclu- 

 sively to the right or principal lobe of the liver. 

 It is formed by three branches. The splenic vein 

 is the smallest, and is added to the vena portae, 

 just as it penetrates the liver on the side of the 

 hepatic duct. The next is made of two 

 branches; of which one returns the blood of 

 the posterior gastric artery, and therefore may 

 be called the posterior gastric vein ; and the 

 other is furnished by the pancreas and duode- 

 num, and therefore is the pancreatic vein. 

 The third and largest branch of the vena 

 portse is the mesenteric vein (x\ which not only 

 collects the blood from all the small intestines, 

 but likewise receives the inferior mesenteric (2), 

 or vein of the rectum, which forms the com- 

 munication that has been described with the 

 pelvic veins. 



" The veins of the left lobe of the liver are 

 furnished in the goose by those which accom- 

 pany the anterior gastric artery, and some 

 branches from the head of the duodenum. 



" The anterior gastric veins produce two small 

 trunks, which enter at the two extremities of 

 the fissure, in the concave surface of the left 

 lobe of the liver, as it lies upon the edge of 

 the gizzard; the veins from the head of the 

 duodenum furnish a small vessel which passes 

 backwards to penetrate the posterior part of 

 the fissure in the left lobe. 



" In the c ock the veins that the left lobe of the 

 liver derives from the anterior gastric, are more 

 numerous than in the goose, 



" The veins of the zone of gastric glands, and 

 of the lower portion of the oesophagus, do not 



* Besides their anastomoses the principal vis- 

 ceral veins are remarkable for their large size in 

 the Diving Birds. Cuvier (Lemons d'Anat. Comp. 

 iv. p. 274 ) has especially noticed the dilatation of 

 the inferior cava of the Grebes (Colymbus), which 

 reservoir he compares with that formed by the 

 hepatic veins in the Seal. 



