Anatomy of the Cat

by Jacob Reighard; H. S. Jennings

—Two or three lymph-glands are found in the fatty mass in the neck beneath the clavotrapezius and levator scapulæ ventralis muscles. These receive lymphatics from the neck and side of the thorax. The vessels which arise from them join those from the head and arm to enter the external jugular vein.

3. Lymphatics of the Thoracic Limbs.

—The lymphatics of the forelimbs begin as a number of vessels on the dorsum and palm of the hand. These all pass toward the radial side, and at about the base of the first metacarpal the vessels from both sides of the hand unite to form two or three main trunks. These pass towards the elbow, accompanying the vena cephalica ([Fig. 130]). There are usually two of these main trunks, one lying on each side of the vena cephalica. They accompany this vein over the shoulder, following that portion which finally joins the external jugular. In the hollow of the shoulder they enter the cervical lymph-glands, one or two lymph-glands imbedded in the fat lying beneath the clavotrapezius and levator scapulæ ventralis in this region. From the cervical lymph-glands a single trunk passes mediocaudad, unites with the lymphatics from the head, and usually (on the left side) with the cranial end of the thoracic duct, and enters the external jugular vein at its junction with the subclavian. The common trunk from the head and arm may enter the jugular separately, but close to the termination of the thoracic duct. On the right side the common trunk is joined by one or more small vessels coming from the lymphatic glands of the thorax and forming the right lymphatic duct.

There is said to be also a deep system of lymphatics in the arm, in addition to the superficial system above [described]; this is said to accompany the branches of the brachial vein. If this system is present in the cat, it is much less easily demonstrated than the superficial system.

4. Lymphatics of the Thorax and Abdomen.

—In the thorax are a number of lymphatic glands which are apparently not constant in number and position. One is commonly found dorsad of the bifurcation of the superior vena cava, one ventrad of the mammary vein, several small ones about the bifurcation of the trachea, one or more in the region of the aortic arch, and a number of small ones scattered in the mediastinum. The vessels from these glands finally join either the right lymphatic duct or the thoracic duct; the details have not been worked out and are probably variable.

In the abdominal cavity a number of mesenteric glands, of considerable size, are found in the mesentery and in the mesocolon. In the mesocolon these are usually separate, forming a chain of glands following the colon about one and a half centimeters from it. In the mesentery the glands are mostly united into a very large one, formerly known as the pancreas aselli; this is the largest lymph-gland in the body. It is a curved structure, four or five centimeters in length, lying in the central region of the mesentery.

Into the mesenteric glands pass lymphatic vessels from the viscera of the abdomen. From the mesenteric glands one or two large lymphatic vessels pass craniodorsad, at first with the portal vein, then dorsad of it. This vessel reaches the dorsal side of the aorta near the cranial end of the kidney, where it enters a large fusiform vessel, the receptaculum chyli, which stretches from the cranial end of the kidney craniad between the crura of the diaphragm into the thorax. The receptaculum receives other lymphatics from the various organs of the abdominal cavity as well as vessels coming from the pelvic region, and from the iliac glands. These lie beside the iliac artery, receive lymphatics from the hind limbs, and send lymphatics craniad to the receptaculum chyli. The latter forms the beginning of the thoracic duct.

The thoracic duct ([Fig. 118], 5, [page 282]) enters the thoracic cavity between the crura of the diaphragm as a continuation of the receptaculum chyli. It lies on the dorsal side of the aorta (a), somewhat to the left. It passes along the aorta, gradually coming to lie more on its left side, and finally leaves that vessel near the aortic arch. The duct continues thence straight craniad along the left side of the œsophagus till it reaches the external jugular vein at its junction with the subclavian. In this region the thoracic duct usually unites with the lymphatics coming from the head and arm, then enters the external jugular vein, or the innominate at the point of union of external jugular and subclavian.

In its passage through the thorax the duct frequently divides into two or three divisions which pass along parallel to each other for a distance, then reunite. Such division into two or three parts is especially frequent just before the union with the jugular vein. The numerous valves in the thoracic duct give it a beaded appearance.