An appreciation of the pathology of the lymphatic system requires a brief allusion here to the latest investigations and conclusions regarding the purpose of the lymph as a fluid and the channels by which it is distributed. Under the term lymph, Hall has included four different types: (1) Tissue lymph, which fills the intercellular spaces throughout the body; (2) circulating lymph, which passes through the lymphatic capillaries into the circulatory system by way of the thoracic duct; (3) chyle, or the peculiar circulating lymph of the intestinal tract, which carries into the general circulation its load of nutritive material; (4) serous lymph, i. e., the contents of the serous cavities. Closely related to the latter are the aqueous humor, the cerebrospinal and the synovial fluids. All these fluids, except chyle, contain at least 95 per cent. of water and nearly 4 per cent. of proteids.
The lymph is the only fluid which comes into contact with all the living cells of the body; it pervades every part of its substance to such an extent that it has been said that the higher animals are essentially aquatic because they practically live in a watery medium. Blood normally comes into contact only with the endothelial cells of the vessels and with those cells in the splenic pulp and perhaps other localities which have to do with its elaboration, and these are but a minute proportion of the total cells of the body. All the rest receive their nutrition and even their oxygen through the lymph, which receives them from the blood. Moreover, nearly all the waste materials of the body are emptied into the lymphatic system, and thus directly or indirectly find their way into the blood to be further extruded. Thus, with the exception of the endothelium, the lymph is the medium of exchange between blood and tissue. In this the lymph and the lymphatics play a role which even for the surgeon must be of the greatest importance.
The amount of lymph which empties into the vena cava from the thoracic duct represents only that which comes from the viscera, bearing its special load of nutritive material. When we consider the communication between the blood-vascular and the lymph-vascular systems, the promptitude with which material injected into the tissues (e. g., salt solution) is taken up by the lymphatics and its effects made known through the bloodvessels, we will better appreciate how deleterious material also can be quickly distributed through the system. The lymph then must be regarded as a fluid derived from the blood by combined filtration and osmosis, which makes its way back into the blood again with equal ease.
Lymph vessels which are sufficiently large to be recognized have thin walls and are provided with valves like the veins, the lymph stream being propelled by a vis a tergo from the heart. Any injury which permits blood to escape will also injure numerous minute lymph vessels; in fact, in such little maneuvers as vaccination the attempt is made to draw lymph alone and not blood. If a large lymph trunk be divided there may be an outpour of lymph, and if this happen to be the thoracic duct the external escape of its lymph stream may seriously interfere with nutrition. Injuries which divide it within the thorax are usually fatal, but it may be divided in the neck by a puncture or stab wound, or during a deep operation. Escape of lymph into the abdominal cavity under similar circumstances gives rise to chylous ascites, and when into the thorax to chylous hydrothorax. In the former case repeated tapping may tide over the emergency and lead to eventual recovery; in the latter, aspiration or even open incision may be necessary. When the thoracic duct has been injured in the neck it may be possible to close the opening with sutures or to suture tissues over it. In a few instances final recovery has followed the formation of a chylous fistula. Injury to this duct is to be recognized by the flow of milky (i. e., chylous) fluid from the wound or from the duct itself. When poured into the abdomen or the thorax the retained fluid has the same milky appearance. It has been suggested to withhold all food in order to favor the spontaneous closure of such an opening, supporting the patient meanwhile by rectal nourishment and by the introduction of milk into the veins. The right lymphatic duct is less liable to injury, and such lesions on the right side would be of less importance.
PLATE XXXI
Diagram of the Nodes and Vessels of the Head and Neck, showing the Regions that are Drained into Each Group of Nodes. Deep structures in red, superficial in black. (Gerrish.)
PLATE XXXII
Diagram of the Nodes of the Right Upper Limb and their Superficial Tributaries, showing the Areas Drained by Each Group. Deep structures in red, superficial in black.