Of the Lymphatics. 



THE Lymphatics have derived their name from the appearance of the fluid 

 contained in their interior (tympha, water). They are also called absorbents, 

 from the property they possess of absorbing certain materials from the tissues, 

 and conveying it into the circulation. 



The lymphatic system includes not only the lymphatic vessels and the glands 

 through which they pass, but also the lacteal, or chyliferous vessels. The lacteals 

 are the lymphatic vessels of the small intestine, and differ in no respect from 

 the lymphatics generally, excepting that they contain a milk-white fluid, the 

 chyle, during the process of digestion, and convey it into the blood through 

 the thoracic duct. 



The lymphatics are exceedingly delicate vessels, the coats of which are so 

 transparent, that the fluid they contain is readily seen through them. They 

 retain a nearly uniform size, being interrupted at intervals by constrictions, 

 which give them a knotted or beaded appearance. These constrictions are due 

 to the presence of valves in their interior. Lymphatics have been found in 

 nearly every texture and organ of the body, with the exception of the sub- 

 stance of the brain and spinal cord, the eyeball, cartilage, tendon, the mem- 

 branes of the ovum, the placenta, and umbilical cord, the nails, cuticle, and 

 hair. Their existence in the substance of bone is doubtful. 



The lymphatics are arranged into a superficial arid deep set. The superficial 

 lymphatics, on the surface of the body, are placed immediately beneath the in- 

 tegument, accompanying the superficial veins ; they join the deep lymphatics 

 in certain situations by perforating the deep fascia. In the interior of the body, 

 they lie in the submucous areolar tissue, throughout the whole length of the 

 gastro- pulmonary and genito- urinary tracts; and in the subserous areolar tissue 

 in the cranial, thoracic, and abdominal cavities. These vessels probably arise 

 in the form of a dense plexiform network interspersed among the proper elements 

 and bloodvessels of the several tissues ; the vessels composing which, as well 

 as the meshes between them, are much larger than those of the capillary plexus. 

 From these networks small vessels emerge, which pass, either to a neighboring 

 gland, or to join some larger lymphatic trunk. The deep lymphatics, fewer in 

 number, and larger than the superficial, accompany the deep bloodvessels. 

 Their mode of origin is not known ; it is, however, probably, similar to that 

 of the superficial vessels. The lymphatics of any part or organ exceed, in 

 number, the veins ; but in size they are much smaller. Their anastomoses 

 also, especially those of the large trunks, are more frequent, and are effected 

 by vessels equal in diameter to those which they connect, the continuous trunks 

 retaining the same diameter. 



The lymphatic or absorbent glands, named also conglobate glands, are small 

 solid glandular bodies, situated in the course of the lymphatic and lacteal ves- 

 sels. They are found in the neck and on the external parts of the head ; in the 

 upper extremity, in the axilla and front of the elbow ; in the lower extremity, 

 in the groin and popliteal space. In the abdomen, they are found in large 

 numbers in the mesentery, and along the side of the aorta, vena cava, and iliac 

 vessels ; and in the thorax, in the anterior and posterior mediastina. They are 

 somewhat flattened, and of a round or oval form. In size, they vary from a 

 hemp-seed to an almond, and their color, on section, is of a pinkish-gray tint, 

 excepting the bronchial glands, which in the adult are mottled with black. 

 Each gland has a layer, or capsule, of cellular tissue investing it, from which 



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