THE LYMPH VASCULAR SYSTEM. 859 
the right pancreatico-gastrie fold of peritoneum, passes behind the neck of the pancreas, and 
ends in the superior mesenteric vein. 
The pancreatico-duodenal vein receives tributaries (vv. pancreatico-duodenalis) from the head 
of the pancreas and the adjacent parts of the duodenum ; it ascends along the superior pancreatico- 
duodenal artery, and terminates in the upper part of the superior mesenteric vein. 
The splenic vein (vy. lienalis) is formed by the union of five or six tributaries which 
issue from the hilus on the anterior surface of the spleen. It passes backwards 
and inwards in the lieno-renal ligament to the kidney, then turning to the right it runs 
behind the upper border of the pancreas and below the splenic artery ; it crosses the front 
of the abdominal aorta, immediately below the origin of the coeliac axis, and terminates 
behind the neck of the pancreas, by joining the superior mesenteric vein to form the 
portal vein. ; 
Tributaries.—It receives the vasa brevia or gastric veins, the left gastro-epiploic vein, 
the pancreatic veins, and the inferior mesenteric vein. Occasionally the coronary vein ter- 
minates 1n It. 
The vasa brevia or gastric veins (vv. gastricee breves) are a series of small venous channels 
which gather blood from the region of the left portion of the great curvature of the stomach ; 
they pass backwards towards the spleen in the gastro-splenic omentum, and terminate either in 
the trunk of the splenic vein or in one of its main tributaries. 
The left gastro-epiploic vein runs from right to left along the lower border of the stomach 
between the layers of the great omentum. At the left extremity of the stomach it enters the 
gastro-splenic omentum, through which it passes towards the hilus of the spleen, and it 
terminates in the cominencement of the splenic vein. It receives tributaries from both 
surfaces of the stomach. 
The pancreatic veins issue from the substance of the pancreas, and terminate directly in the 
splemic vein. 
The inferior mesenteric vein (v. mesenterica inferior) commences, as the superior hemor- 
rhoidal vein, in the venous plexus which lies between the muscular and mucous coats of the 
rectum. The superior hemorrhoidal vein (v. heemorrhoidalis superior) drains the greater part of 
the blood from the hemorrhoidal plexus, through which it communicates with the middle and 
inferior hemorrhoidal veins. It ascends in company with the superior heemorrhoidal artery, and 
between the layers of the meso-rectum, to the brim of the pelvis, where it passes in front of the 
left common iliac artery and becomes the inferior mesenteric vein. 
The inferior mesenteric vein runs upwards on the left of the aorta, behind the peritoneum, 
and in front of the left psoas muscle and the left spermatic artery. Near its termination it 
crosses in front of the left renal vein, and, passing behind the body of the pancreas, ends in the 
splenic vein. Occasionally it terminates in the angle of union of the superior mesenteric and 
splenic veins. 
Tributaries.—In addition to the superior hemorrhoidal vein, of which it is the direct con- 
tinuation, the inferior mesenteric vein receives sigmoid tributaries (vv. sigmoidez) from the 
iliac and pelvic colon, and the left colic vein from the descending colon and splenic flexure. 
THE LYMPH VASCULAR SYSTEM. 
The vessels of the lymph vascular system (vasa lymphatica) contain a colourless 
fluid, rich in white corpuscles, called lymph. In many respects they resemble blood- 
vessels, especially the veins; but unlike veins they communicate with intercellular 
spaces and with serous sacs, and their continuity is interrupted by interposed nodular 
ageregations of lymph tissue which are known as lymph glands (lymphoglandule). 
Lymph is collected in intercellular spaces from which lymph capillaries arise ; 
the latter terminate in lymphatic vessels, which unite together, forming larger 
vessels ; and ultimately two terminal trunks—viz. the thoracic duct and the right 
lymphatic duct—open into the venous system, at the commencement respectively 
of the left and right innominate veins. 
There are no outgoing vessels, but it is customary to speak of afferent (vasa 
afferentia) and efferent (vasa efferentia) lymphatics with reference to vessels 
which enter or leave the interposed glands. 
Lymph vessels, and the spaces in which they commence, merely collect and 
convey lymph. The lymphatic glands act, in part at least, as filters, and possibly 
also some of the white corpuscles are formed in them. 
The greater part, if not the whole, of the lymph of the body passes through 
one or more of the lymph glands before it reaches the blood vascular system. 
Lymphatic spaces.—Lymph spaces are simply intervals or clefts in connective 
