THE STRUCTURE OF THE LYMPHATIC GLANDS. 45 



the structure of the. gland itself, present no external coat. The 

 external tunic of the extra-glandular lymphatics the afferent 

 and efferent vessels appears to leave them almost entirely at 

 their entrance and exit from the organ, and by passing on to the 

 surface of the gland form its capsule. 



This capsule is moderately strong, somewhat smooth on its 

 free, more filamentous on its attached surface, sending inwards 

 from the latter the processes already described, which not only 

 support the larger branches of the vessels before they anastomose, 

 but also bind together and strengthen the substance of the organ. 

 The larger trunks of the arteries and veins, as they pass through 

 the capsule, and plunge into the substance of the gland, carry 

 along with them also a certain quantity of filamentous texture, 

 which is derived from the internal surface of the capsule, and 

 is continuous with the processes which surround the larger lym- 

 phatic branches. 



The middle, or fibrous tunic of the extra-glandular lymphatics, 

 also begins to disappear after these vessels have penetrated the 

 capsule of the gland. It is still sufficiently apparent on the 

 lymphatics near the surface of the organ, but is met with spar- 

 ingly towards the centre. Different glands, however, differ in 

 this respect ; the human intra-glandular lymphatics appearing to 

 me to retain more of their fibrous tunic, than those in the more 

 granular and developed mesenteric glands of the dog and seal. 



It is, however, to the changes which the internal tunic of the 

 intra-glandular lymphatics undergoes, that I shall now more par- 

 ticularly direct attention, as these have hitherto escaped obser- 

 vation, and as upon them depend those appearances and pe- 

 culiarities which are yet unexplained. 



I shall first describe the internal tunic, and afterwards its 

 arrangement. 



If this tunic be traced from the afferent lymphatics, in which 

 it presents the usual structure, into the branches immediately 

 after they have penetrated the capsule of the gland, it is found 

 to become thicker and more opaque. In the short dilated anas- 

 tomosing branches which form the intra-glandular network, this 

 tunic has become so thick and opaque, that the vessels will no 

 longer transmit the light, and appear as if they were stuffed full 



