390. The lymphatic vessels, like the veins, diminish in number as they increase in size, while pursuing their course toward the large veins near the heart, into which they pour their contents. The walls of these vessels have two coats of which the external one is cellular, and is capable of considerable distention. The internal coat is folded so as to form 183 valves, like those in the veins. Their walls are so thin, that these folds give them the appearance of being knotted.
What is represented by fig. 82? By fig. 83? By fig. 84? 390. In what respect do these vessels resemble the veins of the system? Give the structure of their coats.
391. At certain points, the lymphatic vessels pass through distinct, soft bodies, peculiar to themselves, which are called lymphatic glands, which are to these vessels what the mesenteric glands are to the lacteals. The lymphatic glands vary in form and in size. They are extremely vascular, and appear to consist of a collection of minute vessels. These glands are found in different parts of the body, but are most numerous in the groins, axilla, or arm-pits, neck, and cavities of the chest and abdomen.
Observation. From exposure to cold, these glands are frequently enlarged and inflamed. They are known under the name of “kernels.” They are often diseased, particularly in scrofula, or “king’s evil.”
PHYSIOLOGY OF THE LYMPHATIC VESSELS.
392. Though the lacteals and lymphatics resemble each other in their structure and termination, yet they differ as to the nature of the fluids which they convey, as well as the nature of their functions. The lacteals open into the small intestine, and possess the power of rejecting all substances in the passing aliment, but the chyle. The lymphatics, on the contrary, not only imbibe all the various constituents of the body, both fluid and solid, but they sometimes absorb foreign and extraneous substances, when presented to their mouths, as in vaccination.
393. The varieties of absorption are, the In-ter-sti´tial, Rec-re-men-ti´tial, Ex-cre-men-ti´tial, Cu-ta´ne-ous, Res-pi´ra-to-ry, Ve´nous, and the Lac´te-al.
391. Describe the lymphatic glands. What observation is given in regard to these glands? 392–403. Give the physiology of the lymphatic vessels. 392. Explain the difference between the lacteals and lymphatics 393. Name the varieties of absorption.