LYMPHATIC GLANDS 89 



The lymphatic vessels into which the lymph- 

 capillaries poux" theii" contents on its way towards the 

 thoracic duct possess a structure essentially similar to 

 that of a vein (p. 34) ; but tliey difler from a vein in that 

 their walls are thinner, so thin as to be very transparent, 

 are relatively more muscular and are more plentifully 

 supplied with valves, whose structure, however, is the 

 same as in the veins. 



Fig. 29. — Epithelioid Cells Lining, and Chak.acteristic of, the 

 Lyjiphatics. 

 The outline of the cells has been brought into view by means of 

 nitrate of silver, which does not stain the nuclei ; the latter therefore 

 are not shown. 



3. The Structure and Function of Lymphatic 

 Glands. — Lymphatic glands occur at more or less frequent 

 intervals along the course of the lymphatic vessels. They 

 are of very variable size, being somewhat rounded when 

 small and when large having more or less the shape of a 

 bean. The afferent lymphatic vessels enter the glands 

 by several branches on its more convex side, and emerge 

 in diminished numbers as efferent vessels from the opposite 

 side. Blood-vessels enter and leave the glands side by 

 side with the efferent lymphatic ve.ssels. 



Each gland is covered externally by a capsule or coat 

 of connective tissue, with which some unstriated muscle 

 fibres are not infrequently mixed. This capsule sends 

 projections, called trabeculae, inwards and towards the 

 centre of the gland which divide it up into compartments 

 or alveoli, the compartments being very regularly ar- 

 ranged at the outer portion or cortex of the gland and 



