118 



THE LYMPHATICS. 



Nerves. — Bert and Laffont have demonstrated the existence of vaso-motor 

 nerves in the chyhferous vessels of the Dog. Galvanization of the solar plexus 

 or the o-reat splanchnic nerve, causes contraction of the wall of these lymphatics. 

 (The lynipiiatic spaces surrounding vessels are designated perivmcular canals. 

 Lymphatics originate in lacunae, or spaces between the fibres of the connective 

 tissues, and these are lined by endothelial cells ; they are drained by lymphatic 

 vessels — the arrangement presenting an analogy to the vascular system of insects 

 and Crustacea. Masses of protoplasm — the connective-tissue corpuscles — abound 

 in many tissues, occupying some of the interstitial spaces ; the latter communicate 

 freely with each other, the communication being tubes in the form of small 

 pores or canals. The fluid drained off is the lymph, which passes into gradually 

 enlarging canals.) 



Lymphatic Glands. 



The lymphatic glands are ovoid, spherical, or discoid bodies of medium 

 consistency, grey, rosy, or red-coloured, and sometimes quite black, and which 

 at several points intercept the course of the lymphatic vessels. 



Their number is considerable, and they are rarely single, but most frequently 



Fig. 394. 



Fig. 393. 



LVMPHATIC GLAND. 



a, a, The fibrous tissue that forms its exterior; 

 6, h, superfioial vasa inferentia ; c, c, larger 

 alveoli, near the surface, d, d, smaller alveoli 

 of the interior , e, e, fibrous walls of the alveoli. 



SIMPLE LYMPHATIC GLAND. 



a, The capsule with sections of lym- 

 phatics, d, d, passing through it ; 

 6. lacunar ami intercommunicating 

 passages, permeafed by the lymph, 

 and forming the superficial lymph- 

 path of Frey ; c, nucleus, or me- 

 dullary portion, with section of 

 blood-vessel in the centre. 



are collected in groups along the blood-vessels. They are always larger in youth 

 than in old age. 



All the vessels of the lymphatic system are provided with at least one gland 

 on their course, and some even pass through two or three before opening into 

 the thoracic duct or great lymphatic trunk. (Jn reaching these glands, they 

 plunge into their substance by ramifications, appearing on the opposite point 

 after being reconstituted into several principal canals, which are generally larger 

 and less numerous than the original vessels. The latter take the name of 

 afferents (vasa inferentia or afferentia) ; the others are named efferents {vasa 

 ifferentia), becaase they leave the gland to reach the central canal. 



Structure. — The structure of the glands is extremely complex. 



They have an envelope of connective tissue (continuous with the tunics of the 



