206 ANATOMY OF VERTEBRATES. 



edge of the pelvis, each of these two veins forms two branches ; 

 one of which collects the blood of the lower extremity, as here- 

 after described ; the other passes straight downward imbedded in 

 the substance of the kidney, and admits the several emulgent 

 veins, Avhich are very large, and are seen to pass for some way 

 obliquely in the kidney before their termination. Sometimes the 

 emulgent veins are double, as in the figure, ib. u. The limb- 

 vein sends off a descending branch into the renal tissue which, 

 when arrived at the lower end of the kidney, di\ddes into three 

 branches ; one receives the blood of the muscles of the tail and 

 parts adjacent ; another accompanies the ureter to the side of the 

 rectum, and is distributed about the anus and parts of gene- 

 ration, answering to the hcEmorrhoidal veins ; the third, ib. v, v, 

 passes inward to the middle line between the kidneys, and there 

 unites with the corresponding branch of the opposite side. These 

 are the branches which have been supposed to carry venous 

 blood into the kidneys, for the purpose of supplying material 

 for the urinary secretion. The vessel which is in this manner 

 produced, ib. z, receives all the blood of the rectum from the anus 

 to the orio'in of the coeca, anastomosino; below with the branches 

 of the ha3morrhoidal veins ; and at the upper part of the rectum, 

 it becomes continuous with the trunk of the veins of the small 

 intestines, ib. x, forming 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 

 almost indifferently into the vena cava and vena port^e, ic ; for 

 the anastomosing vessels are sufficiently large to admit the ready 

 passage of a considerable column of blood in proportion to the 

 whole mass which circulates in the body of the bird ; for instance, 

 in the Goose the communicating 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. Besides their anastomoses the princij^al 

 visceral veins are remarkable for their large size in the Diving 

 Birds. 



' 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 porta3 does not require any 23eculiar 

 preparation by circulation in the spleen or other viscera to fit it 

 for the secretion of bile. 



* The vena portce, ib. w, belongs almost exclusively to the 

 right or principal lobe of the liver. It is formed by three 

 branches. The splenic vein is the smallest, and is added 



