ORGANS OF THE BODY. 



417 



lary substance ( 224), eo that there can be no f doubt as to the farther 

 course of the injection fluid: it fills namely this network of lymph pas- 

 sages also, while the lymph tubes of the medullary substance remain 

 colourless so long as only slight pressure is used. 



From the mode of termination of the injection we perceive that the 

 vas efferens must take its rise from the passages of the medullary portion 

 of the gland, in that it is at last filled by the fluid employed. It is also 

 possible at times to drive the liquid back through the vas efferens into the 

 lymph node by overcoming the opposition of the valves. Retrograde 

 injections of this kind impel the matter used first into the reticulated 

 passages between the lymph-tubes of the medulla, and from thence further 

 on into the investing spaces of the follicles. 



The confluence of these medullary lymph streams, however, to form a 

 branch of the vas efferens is a point very difficult of detection (fig. 409). 



The latter vessel which leads into the connective-tissue at the hilus 

 undergoes there further division into branches, as has been already 

 remarked. These may vary greatly according to the size of the gland, 

 and the greater or less development of 

 the fibrous nucleus of the latter. En- 

 closed within the partitions of the 

 medulla, the last branches of the vas 

 efferens (e) are observed to course along 

 in the form of tubes of various calibre, 

 whose walls are, as a rule, fused with 

 the surrounding connective-tissue (/). 



Finally, on penetrating further into 

 the gland we observe that the partitions 

 which contain such ramifications of 

 the vas efferens become subdivided more 

 and more, forming series of diverging 

 bands, so that the lymph stream is no 

 longer enclosed within an envelope, 

 and exhibits all the reticular characters 

 and irregular limitations (d) charac- 

 teristic of the hollow cavities of the 

 medulla. In fact, there can be no 

 doubt that we have before us the origin 

 of the vas efferens from the cavernous 

 portion of the medulla of the gland. 



It may be remarked, further, that the vasa efl'erentia on their exit from 

 the lymph nodes present much variety of appearance, depending upon the 

 size of the organ and the development of the connective-tissue nucleus in 

 the neighbourhood of the hilus. Thus in the hilus of the large mesenteric 

 glands of the ox a regular plexus of peculiar, very tortuous, and knotted 

 vessels has been seen by Koelliker, and Teichmann also gives drawings of 

 exceedingly complicated vasa efferentia. 



From the foregoing description, then, the following conclusions may be 

 drawn. The vessel leading into the gland pierces its capsule in the form 

 of a canal, and opens into the investing spaces of the follicle. These 

 lead then into the lymph passages of the medullary portion, from the 

 confluence of which the radicals of the vasa efferentia enclosed within the 

 substance of the converging partitions are formed. 



From this we see that really independent lymphatic vessels do not 



Fig. 409. From the medullary substance ot 

 an inguinal gland of a large dog. a, 

 lymph tubes; 6, empty reticulated passages 

 of the medulla; c, the same filled ; d, tran- 

 sition into the commencement of a twig of 

 the vas efferens; e, the latter coursing along 

 within a fibrous septum //. 



