ABSORPTION FROM THE TISSUES IN GENERAL.
Lymphatic Vessels.—Now in every organ and tissue there is a set of vessels, called lym phatic vessels, precisely similar to the lacteal vessels of the mesentery; and they are connected with lymphatic glands just as the lacteals are connected with mesenteric glands. These lymphatic vessels contain a fluid called lymph.
What lymph is must be properly understood. The blood flows through' the whole body, being buted in small vessels with extremely thin walls. As the blood flows in these fine vessels through a muscle, for example, it oozes through the delicate walls, so that the fibres of the muscle are bathed in the and the muscle can select the nourishment which it requires. ,Tust as a river flowing through a large plain may be made to water the whole of it, by a set of channels being cut here and there throughout it, along which the water may be caused to flow, and be thus brought near every part of the fields. It is the presence of lymph among the tissues that gives to them their ness and moisture. More fluid escapes from the vessels than may be necessary for the nourishment of the tissues. The excess must be removed. It passes into the lymphatic vessels which abound in muscle. Since the fluid has bathed the tissue, it will have picked up materials from the muscle, principally waste substances which have been produced by cular work. This excess of nourishment, along with the waste substance removed with it from the tissues, forms lymph. The lymph is not cast out of the body; it is returned to the blood. But even as the chyle from the intestine Was not in a fit condition for immediately joining the blood-stream, and was passed through the mesenteric glands to be properly worked up, so the lymph is carried to lymphatic glands, where it undergoes certain processes to fit it for being poured into the blood. Here, then,
is another example of the marked economy ex hibited in the body. Nothing is cast out in the ordinary healthy body that can be of further service in the system. As to the characters of lymph, they resemble those of chyle. It is a whitish fluid, slightly yellowish, clots readily, and contains white cells, like the white cells of the blood, but it does not contain the minute globules of fat that abound in chyle.
It has been said that lymphatic channels exist in every organ and tissue of the body ; and perhaps it will give some idea of their abundance when it is said that it hag been esti mated that the quantity of fluid picked up from the tissues by their agency and restored to the circulation in 24 hours is equal to the bulk of all the blood in the body.
The lymphatic vessels unite to form larger and larger vessels, and in the end join the thoracic duct, with the exception of the lym phatics of the right side of the head and chest and right arm. These latter form a short wide trunk—the right lymphatic duct—which opens into the junction of the jugular vein of the right side, coming from the head, with the vein com ing from the right arm, a similar position to that of the thoracic duct on the left side. In Fig. 126, 5 points to the vein formed by the junction of the veins of the head and arm. Thus all the lymphatic vessels of the lower limbs, of the belly, of the left arm, and of the left side of the head and chest, and all the lacteal vessels from the intestine, pour their contents into the thoracic duct, while the lymphatics of the rest of the body join the right lymphatic duct.