5 THE LYMPHATICS
The office of the lymphatics.-Their origin, and construction.-Lymphatic glands.-Lacteals.-Difference between lymphatics and lacteals.-Different kinds of lymphatics.-Radicles.-Chyle.-Lymph.-General views of absorption in the system
210. What are the lymphatics?HBH 82.1
They are minute, transparent vessels, uniform in size, having various valves. They constitute what is called the absorbent system. They are named from the substance they convey, lymph, a watery fluid, which they gather and pour into the blood.HBH 82.2
211. What is the office of the lymphatics?HBH 82.3
Their office is to collect the nutritive products of digestion from the alimentary canal, and the effete, disorganized matter from all parts of the body, and convey them into the venous blood. They also have the power of absorbing substances applied to the skin. Green leaves of tobacco applied to the abdomen will often produce distressing sickness. Poisons thus taken up by the blood from the surface of the body, being undiluted by the juices of the gastric cavities, pass directly into the circulation, and are therefore more powerful than when modified by passing through the internal absorbent vessels. In some cases where the passage from the mouth to the stomach has been closed by disease, nutriment has been infused into the system by means of a bath of warm milk. Shipwrecked sailors in an open boat have slaked their thirst by wetting their clothing in salt water, or what is better still, by being wet in a rain storm.HBH 82.4
212. What is the origin of the lymphatics?HBH 82.5
They originate in a delicate net work, and are distributed throughout the skin and the various surfaces and internal structure of organs. There is scarcely a part in the whole body where these lymphatic vessels are not found, but, in some parts they are so extremely small that they cannot be discovered without the aid of a microscope. In the brain, where they are supposed to exist, they have not as yet been discovered even by the microscope. They are remarkable for their uniformity in size. They are of a knotted appearance, and very frequently divided into two nearly equal branches. They proceed in nearly straight lines toward the root of the neck.HBH 82.6
213. What is connected with these lymphatic vessels?HBH 83.1
They are intercepted in their course by numerous oblong bodies, called lymphatic glands. These are small, oval bodies, of a reddish ash color, and vary in size from one twentieth of an inch to an inch in diameter. They are somewhat flattened, and are larger in young persons than in the adult, and are smallest in old age. These glands are situated in different parts of the body, but abound mostly in the thorax and abdomen. Leaving these, the lymphatics converge from all parts of the body so as to pour their contents into tubes, which open into large veins leading to the heart, near the bottom of the neck.HBH 83.2
214. What is the construction of the lymphatics?HBH 83.3
Like arteries and veins, they are composed of three coats, frequently connected together, and having valves. It is these valves that give to the lymphatic vessels their knotted appearance. These valves are most numerous near the lymphatic glands. The lymphatics are smallest in the neck, larger in the upper extremities, and still larger in the lower extremities.HBH 83.4
215. What are the lacteals?HBH 84.1
They are the lymphatic vessels of the small intestines, which convey the milk-like fluid called chyle to the thoracic duct. These are the nutritive absorbents, and they are connected with the numerous glands of the mesentery. It is in the small intestines that most of the alimentary absorption of the body is effected.HBH 84.2
216. What is the difference in the functions of the lacteals and the lymphatics proper?HBH 84.3
The lacteals convey nutritive or new matter into the mass of blood, to replenish the tissues; the lymphatics take up and return to the blood the surplus nutrient materials, and also old or waste particles, in order that they may be used in the secretions of the body or got rid of at the excretory outlets. The function of the lacteals is called the absorption of composition, that of the lymphatics the absorption of decomposition. The lymphatics proper, pervade, as before shown, the whole body, arising in great numbers from the external skin, from all the internal membranes, vessels, and cavities, and from the substance of all the organs. But the lacteals arise only from the mucous membrane of the alimentary canal, and principally from the mucous membrane of the small intestine. There is, however, no difference in the structure of a lymphatic and that of a lacteal; but one elaborates chyle, and the other lymph.HBH 84.4
217. How many kinds of lymphatics are there?HBH 85.1
Two: the superficial and deep. The superficial follow the course of the superficial veins, and they join the deep lymphatics. The glands of these superficial vessels are placed in the most protected positions, as in the hollow of the ham and groin, and on the inner side of the arm. The deep lymphatics accompany the deep veins.HBH 85.2
218. What is the principal center of the lymphatic system?HBH 85.3
The thoracic duct, or receptaculum chyli. It commences in the abdomen, and ascends through the diaphragm to the root of the neck, and then turns forward and downward, pouring its contents into the venous blood just before it enters the right auricle of the heart. The thoracic duct is some eighteen inches in length, and in size about equal in diameter to a goose-quill. Its termination is provided with valves to prevent the admission of venous blood. Before emptying its contents into the blood, it receives several large branches, or trunks, from the lacteals, and the lymphatic branches, from nearly all parts of the body. It is the common trunk of all the lymphatic vessels of the body, except those of the right side of the head, neck, and chest, and right upper extremity, the right lung, right side of the heart and the outer surface of the liver. These empty into the right lymphatic duct, and this empties into the venous blood-vessels of the right side of the chest near the heart.HBH 85.4
219. Are the lymphatics the only absorbent vessels?HBH 85.5
No; the radicles, or small veins, perform a very important function in the stomach, by the rapid absorption of the watery portion of all liquids placed there. It thus conveys them to the general circulation without their passing through the circuitous route taken by the food.HBH 85.6
220. What can you say in general terms of the lymphatic system?HBH 86.1
It is an appendage to the venous system, furnishing it with all the assimilating materials by which the body is nourished, as well as conveying to it the effete substances which are to be eliminated from the vital domain. These two systems are connected at several points, and the structure of the lymphatic vessels much resembles that of the veins. The venous capillaries and the lymphatics appear, to some extent, to reciprocate in function, and the lymphatics always empty their contents into the veins. In the lymphatics, as in the arterial and venous systems, the nerves of organic life are distributed, and they preside over all their functions. In the lymphatic vessels some of the most important changes take place.HBH 86.2
221. What is chyle?HBH 86.3
It is a liquid substance, composed of digested food, and is prepared for nutrition in the mesenteric glands. It is of a milky-white color, and is of the same chemical composition, whatever may be the food from which it is formed. It is not, however, of the same vital quality. That formed from animal food, when taken from the body undergoes putrefaction in three or four days, while that selected from vegetable food will resist decomposition for several weeks.HBH 86.4
222. What is lymph?HBH 86.5
It is a watery fluid, differing from chyle in its color, being almost colorless, and differing also in the fact that the lymph is made mostly of decomposed matter, while the chyle is always formed from new matter. This lymph thus formed, is mostly, if not entirely waste matter, and thrown off through the excretory ducts.HBH 87.1
223. Are the lymphatics and lacteals the only organs that absorb nutrition?HBH 87.2
No; in the mucous membrane of the lungs and stomach, the thin fluids are taken up by the veins.HBH 87.3
224. What is the general view of the absorption in the system?HBH 87.4
The extremities of veins act as absorbent vessels, taking up the greater portion of useless, injurious, or worn-out matters; the lymphatic vessels return the unused or surplus nutritive matter; they also serve as helpers to the veins when they are obstructed, or their task imperfectly performed. The elements of the blood in the capillary system pass through the coats of these vessels and undergo chemical, vital changes. Such elements as are needed, repair the waste and build up the structures of the body. Other elements are separated and carried back into the circulation, to be changed or thrown off.HBH 87.5
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