LYMPHOID ORGANS 



705 



cells are present in the sinuses. The lymph-gland is made up of four distinct elements : lymphoid 

 elements, Ij^mphatic capillaries, supporting structures, and blood-vessels. 



The lyrn-phoid elements (fig. 551) are arranged as follicles and as cell-strings. The follicles 

 he around the circumference of the gland, and form the cortex [substantia corticalis]. The cell- 

 strings or medullary cords are irregular cords of cells which extend from the follicles through the 

 central or medullary portion [substantia meduUaris] of the gland. The follicles and medullary 

 cords are made up, as are the solitary follicles, of round lymphoid cells. 



{ 



Fig. 552. — Surface View and Section of a Lymph-node showing the Peripheral and Cen- 

 tral Sinuses. (After Teichmann.) 



The lymphatic vessels (fig. 551) enter the lymph-gland as several vasa afferentia, and leave 

 it, at the hilus, as the vasa efferentia. The vasa afferentia spread out in the cortical portion 

 of the gland into an extremely rich plexus of wide capillaries which surround the follicles, 

 forming the peripheral sinus. The capillaries do not enter the follicle. This plexus continues, 

 around the follicles, into the medullary portion where it forms again a rich plexus, the medullary 

 sinus, in the spaces around the medullary cords (fig. 552). At the hilus the medullary capil- 

 laries collect into larger vessels and emerge as the vasa efferentia. 



The supporting structures consist of a fibrous capsule surrounding the gland, from which 

 trabeculae or septa pass in, around and between the follicles and cords. From the septa, a 

 fine reticulum passes into the follicles and cords, where it forms a rich dense meshwork, in the 

 interstices of which lie the lymphoid cells. The capsule and trabeculse are made up of white 

 fibres, elastic fibres and smooth muscle-fibres. 



