48 THE STRUCTURE OF THE LYMPHATIC GLANDS. 



These various appearances may be explained by the following 

 facts. In some lymphatic glands the meshes are elongated, in 

 which case no force short of what is sufficient to burst the vessels 

 can obliterate tho vascular appearance. The mtra-glandular 

 lymphatics, like those in other parts, are liable to be over-distended 

 with injections, or by their own contents, so that short vessels or 

 rounded meshes, more especially after great distention, assume 

 the appearance of globular cavities. 



There is another apparently cellular appearance, which is not 

 met with in the human lymphatic glands, but in some of the 

 lower mammals, which is produced by another cause, the partial 

 or entire obliteration of some of the meshes, so as to produce 

 cavities more or less extended, with bars or threads passing from 

 wall to wall, the lymphatics opening into them. This is the con- 

 version of a network of lymphatics into cavities and connecting 

 threads, by a process of absorption similar to that which I have 

 to describe as occurring in the placental decidua.* 



The external surfaces of the intra-glandular lymphatics are 

 closely applied to one another. They are strengthened here and 

 there by fibrous bundles, the remains of the middle tunic. These 

 fibres are most distinct towards the surface of the glands, and at 

 the angles formed by the junction of one lymphatic with another ; 

 and when viewed in thin sections, seem to form arches inclosing 

 circular or oval spaces, like the fibrous matrix of the human 

 kidney. 



The description usually given of the arrangement of the blood- 

 vessels in the lymphatic glands is sufficiently correct. The ulti- 

 mate capillaries, as I have observed, do not ramify in the sub- 

 stance of the germinal membrane of the intra-glandular lymphatics 

 but are merely in contact with its external surface. In this re- 

 spect they resemble the ultimate ducts of the true secreting glands. 



The capillary network which surrounds the intra-glandular 

 lymphatics is as fine as that which supplies the ultimate secreting 

 ducts, and for the same purpose in both, to afford matter for the 

 continued formation of secreting epithelium on the internal sus- 

 face of the germinal membrane. 



* See Page 61. 



