THE MICROSCOPE IN ANIMAL HISTOLOGY. 207 



villus is unusually broad, there may be more than one 

 lacteal. The lacteals absorb the fluid known as chyle. 

 They are blind ducts, and nitrate of silver injections show 

 them to have the same structure as other lymphatics. 



The lymphatic radicles are widely disseminated through 

 all the tissues and organs of the body. They take up nu- 

 tritive fluids, either from the alimentary canal, or such as 

 have transuded from the capillaries into the interstices of 

 the body, mingled with the products of decomposition, 

 and convey them into the general circulation. Hyrtl's 

 method of demonstrating these radicles is by passing a 

 fine canula into the tissue containing lymphatics and forc- 

 ing the injection by gentle pressure. They are either net- 

 works, analogous to capillaries, or blind passages which 

 unite in reticulations. The structure of the vessels has 

 already been described, page 201. Lymphatics and capil- 

 laries do not communicate directly. A lymph-canal may 

 be surrounded by capillaries, or run alongside of a capil- 

 lary, or a lymphatic sheath may envelop a bloodvessel. 

 This latter plan is seen in the nervous centres, and has 

 been called by His the perivascular canal system. 



The larger lymphatic trunks are interrupted by nodular 

 and very vascular organs, the lymphatic glands. These 

 consist of the reticular connective tissue already described, 

 surrounded by an envelope of ordinary fibrous tissue. One 

 or more afferent lymphatic vessels penetrate the capsule, 

 or envelope, and similar efferent vessels make their exit 

 from the other side. Frey describes these glands as con- 

 sisting of a cortical portion, follicles, and a medullary 

 portion composed of the tubes and reticular prolongations 

 of the follicles (Plate XXII, Fig. 162). There is a corn- 

 plicate system of communication between the follicles. 

 The afferent vessel opens into the investing spaces of the 

 follicle. These lead into the lymph-passages of the med- 

 ullary portion, from the confluence of which the radicles 

 of the efferent vessels are formed. The lingual follicular 



