The Lymphatic System 



91 



may be. seen by ocdinary dissection, the structures which appear in 

 this way in being the lymph.glands, or lymph nodes, centres of cell 

 formation, occuring in the course of the conducting vessels. These 

 as superficial structures are found either singly, as in the head and 

 neck, or more or less grouped, as in the axillary and inguinal spaces. 

 As deep structures they are conspicuous in the intestinal mesen- 

 teries, and in the walls of the digestive tube, occuring in the latter 

 chiefly as continuous masses of lymph, follicles, as, for example, 

 in the walls of the sacculus rotundus, the vermiform process, or the 

 tonsil; or, again, as aggregated lymph follicles (Peyer's patches) 

 at various points in the intestinal wall. 



The conducting portion of the 

 system comprises an extensive 

 series of canals, beginning as lym.- 

 phatic capillaries in peripheral 

 organs, and ending as lymphatic 

 trunks which empty into the great 

 veins. The lymphatic trunks of 

 the anterior portion of the body are 

 designated from their association 

 with the corresponding veins as 

 jugular and subclavian. They 

 enter the venous system on either 

 side at the point of junction of the 

 internal and external jugular veins 

 or of the common jugular and sub- 

 clavian (Fig. 82). 



The lymphatic vessels of the 

 posterior portion of the body, 

 including the intestine, unite to form a common canal, the thoracic 

 duct. The latter lies for the most part between the aorta and the 

 vertebral column, and traverses the thorax in this position to enter, 

 the venous system at the same point as the jugular and subclavian 

 trunks of the left side. 



The lymphatic capillaries are terminal, absorptive vessels, 

 differing from blood capillaries both in the.jcha,racter of their walls 

 and in their relations to other portions of the system, siiice they 

 are -wot interposed as in the vascular systein between "stessels of a 

 larger order. The lymphatic vessels connecting the capillaries 



- Fig. 48. Homologies of male (A) and 

 female (B) urinogenital systems, b, 

 urinary bladder; cc, crura clitoridis; cp, 

 crura penis;' dd, ductus deferens; ep, 

 epididynxis; k, kidney; ov, ovary; r, 

 rectum; t, testis; tu, uterine tube; u, 

 urethra- ut, uterus ;ur, ureter; va, vagi na;, 

 vs, seminal vesicle; vs', vestibulura. 



