ioi8 



A MANUAL OF ANATOMY 



(i) a plexus of lymph-capillaries, (2) blood-capillaries, surrounded by lym- 

 phocytes, within connective-tissue septa, and (3) a lymph-sinus. 



Each lymph-gland is connected with several lymphatic vessels. Those 

 which enter the gland are known as afferent vessels, and they open into the 

 peripheral or cortical part of the lymph-sinus. Those which emerge from 

 the gland are termed efferent vessels, and they arise in the central or medullary 

 part of the lymph-sinus. In no case does a lymphatic vessel pass uninter- 

 ruptedly through a lymph-gland. The gland is a station in the path of a 

 lymphatic vessel, which represents the terminus of that vessel, but not the 

 terminus of the lymph. That fluid, after leaving the afierent vessel, flows 



Afferent Lymphatics 



Fibrous Coal 



Efferent Lymphatics 



Fig. 419. — Diagrammatic Section of Lymphatic Gland (Sharpey, from 



Quain). 



in succession through the cortical and medullary parts of the lymph-sinus, 

 and from the medullary part it flows into the efferent vessels. It is there- 

 fore, so far as the lymph is concerned, a case of, so to speak, changing car- 

 riages at a glandular station. During this process any injurious matter is 

 taken up by the branched cells (phagocytes) of the lymph-sinus, and the 

 lymph is furnished with a contingent of lymphocytes 



Structure of Lymphatic Vessels. 



A l3niiphatic vessel, of large size, consists of three coats — inner, middle, 

 and outer. The inner coat (tunica intima) consists of a longitudinal network 

 of elastic fibres, lined with endothelial cells. The middle coat [tunica media) 

 consists of plain muscular and elastic tissues, disposed for the most part 

 transversely. The outer coat [tunica externa) consists of (i) longitudinal 

 bundles of connective tissue, and (2) plain muscular and elastic fibres, dis- 

 posed for the most part longitudinally, lined with endothelium. 



Lymphatic vessels are furnished with bloodvessels and nerves. Most of 

 them are also provided with valves, similar to those of the veins. Each valve 

 consists of two semilunar segments, facing one another, which are foldings of 

 the inner coat, containing connective and elastic tissues. They project 

 slightly towards each other, and their free edges are directed in the course of 

 the lymph-stream. The valves are situated at short intervals, and they serve 

 to prevent reflux of lymph. When a lymphatic vessel becomes distended it 



