THE ABSORBENT SYSTEM 429 



smaller. The spaces are almost completely filled with masses of material 

 consisting of a net-work of very delicate connective tissue, in which 

 white cells (4) of various sizes are entangled. This sort of tissue is called 

 "adenoid", or gland tissue, from the Greek, adeen, a gland. But the 

 masses of tissue do not quite fill the spaces. Between the outer surface 

 of the mass and the wall of the space are channels (5), and the channel 

 round one mass communicates with that of another, and those round the 

 edge communicate with those in the centre, so that the gland might be 

 looked upon as a mass of gland tissue broken up into numerous little 

 clumps by a series of irregularly winding and communicating channels. 

 The channels, moreover, are 

 not perfect fair-ways. They 

 are crossed and recrossed by 

 spans of the delicate tissue of 

 the gland, so that the whole 

 structure becomes not unlike 

 that of a sponge. Now the 

 lacteal vessels join the mes- 

 enteric gland at the margin 

 or outside (l), and pour their 

 fluid contents into the chan- 

 nels there. From them the 

 fluid filters its way to the 

 channels of the centre, bath- 

 ing and penetrating the gland 

 tissue in its course, and finally joins other vessels (2), by which it is 

 carried away from the gland. Through these comparatively free channels 

 the chyle or lymph makes its way, easily entering the gland by the 

 afferent, and escaping by the efferent vessels, and it then carries away 

 from the gland but few leucocytes. When, however, the pressure of the 

 fluid entering the gland is augmented, either by the process of digestion 

 and the contraction of the villi in the case of the lacteals, or by active 

 muscular movements in the case of the lymphatics, the lymph then per- 

 colates the substance of the gland and carries off with it by the efferent 

 vessels large numbers of white cells, which are swiftly poured into the 

 blood, and are believed to constitute one of the sources from which the 

 blood corpuscles are recruited. 



The main agents in effecting the movement of the lymph along its 

 vessels are: (l) The force of the heart, which drives the plasma through 

 the walls of the blood-vessels into the tissues; (2) the muscular move- 

 ments of the body, generally aided by the valves present in all lymphatic 



Fig. 183. Section of Lymphatic Gland (diagrammatic) 



1 Afferent Lymph Vessel. * Efferent Lymph Vessel. 3 Cor- 

 tical Substance. 4 Lymphatic Tissue. Lymph Path. 

 6 Trabeculae sent in from 7 Fibrous Capsule. 



