THE VASCULAR SYSTE^f. 



87 



Terminations of Lymphatics. The lymphatics, including the lacteals. discharge 

 their contents into the veins at two points : namely, at the angles of junction 

 of the subclavian and internal jugular veins: on the left side by means of the 

 thoracic duct, and on the right side by the right lymphatic duct. (See description 

 of lymphatics on a subsequent page.) 



Lymphatic glands (conglobate gland*) are small oval or bean-shaped bodies, 

 situated in the course of lymphatic and lacteal vessels, so that the lymph and chyle 

 pass through them on their way to the blood. They generally present on one 

 side a slight depression the hilum through which the blood-vessels enter and 

 leave the interior. The efferent lymphatic vessel also emerges from the gland at 

 this spot, while the afferent vessels enter the organ at different parts of the 

 periphery. On section (Fig. 63), a lymphatic gland displays two different struc- 

 tures: an external, of lighter color the cortical; and an internal, darker the 

 medullary. The cortical structure does not form a complete investment, but is 

 deficient at the hilum, where the medullary portion reaches the surface of the 

 gland; so that the efferent vessel is derived directly from the medullary structure, 

 while the afferent vessels empty themselves into the cortical substance. 



Lymphatic glands consist of (1) a fibrous envelope, or capsule^ from which a 

 framework of processes (trabecuke) proceed inward, dividing the gland into open 

 spaces (alveoli) freelv communicating with each other ; (2) a quantity of adenoid 

 tissue occupying these spaces without completely filling them ; (3) a free supply 

 of blood-vessels, which are supported on the trabeculse ; and (4) the afferent and 

 efferent vessels. Little is known of the nerves, though Kb'lliker describes some 

 fine nervous filaments passing into the hilum. 



The capsule is composed of a layer of connective tissue, and from its internal 

 surface are given off a number of membranous septa or lamellae, consisting, in man, 

 of connective tissue, with a small admixture of muscular fibre-cells ; but in many 

 of the lower animals composed almost entirely of involuntary muscular fibre. 

 They pass inward, radiating toward the centre of the gland, for a certain distance ; 

 that is to say, for about one-third or one-fourth of the space between the circum- 

 ference and the centre of the gland. 

 They thus divide the outer part of its 

 interior into a number of oval compart- 

 ments or alveoli (Fig. 63). This is the 

 cortical portion of the gland. After 

 having penetrated into the gland for 

 some distance, these septa break up into 

 a number of smaller trabeculae, which 

 form flattened bands or cords, interlacing 

 with each other in all directions, forming 

 in the central part of the organ a num- 

 ber of intercommunicating spaces, also 

 called alveoli. This is the medullary 

 portion of the gland, and the spaces or 

 alveoli in it not only freely communicate 

 with each other, but also with the alveoli 

 of the cortical portion. In these alveoli 

 or spaces (Fig. 64) is contained the 

 proper gland-substance or lymphoid 

 tissue. The gland-pulp does not, how- 

 ever, completely fill the alveolar spaces, but leaves, between its outer margin and 

 the trabeculne forming the alveoli a channel or space of uniform width through- 

 out. This is termed the lymph-path or lymph-sinus (Fig. 66). Running across it 

 are a number of trabeculae of retiform connective tissue, the fibres of which are, 

 for the most part, covered by ramified cells. This tissue appears to serve the 

 purpose of maintaining the gland-pulp in the centre of the space in its proper 

 position. 



FIG. 63. Section of small lymphatic gland, half- 

 diagrammatioally given, witn the course of the 

 Ivmph. a. The envelope. b. Septa between the fol- 

 licles or alveoli of the cortical part. c. System of 

 septa of the medullary portion, down to the hilum. 

 d. The follicles, e. Lymph-tubes of the medullary 

 mass. /. Different lymphatic streams which sur- 

 round the follicles, and flow through the interstices 

 of the medullary portion, g. Confluence of these 

 passing through the efferent vessel, ft, at the hilum. 



