The Mesenteric Glands are seated in the fat, between the layers of the mesentery, near the branches of the blood-vessels. They are commonly scattered over the mesentery, at a little distance from each other; but there are seldom any observed within two or three inches of the intestines. They differ from each other in size, some being about half or two-thirds of an inch in diameter, while others are so small as to be traced with difficulty. Their structure is the same as that of the absorbent glands in other parts of the body, but they are generally flatter, and are of a pale colour. When filled with chyle, they are nearly as white as the fluid contained in them. The lacteals, having passed through these glands, proceed forward, and by anastomosing form a set of trunks, which, together with those of the lymphatics, unite and constitute the thoracic duct, which ultimately opens into the subclavian vein. Much discussion has arisen as to the mechanism by which the chyle is made to pass forward through the lacteal system: capillary attraction would appear to have some influence in the operation, since absorption continues after death; during life, the pressure of the abdominal muscles, and the pulsation of the arteries, no doubt contribute to the effect.

In the interior of the thoracic duct, and in the lacteals, there exist valves, so disposed as to permit the fluid to pass forward towards the subclavian vein, but to prevent its return.