MEDULLARY LYMPH-SINUSES. 87 



afferent lymph-vessels, lymph-sinuses, dense lymphoid tissue, 

 efferent lymph-vessels, and bloodvessels. Two regions can be 

 distinguished in them, a dense peripheral region, the cortex, 

 and an opener central region, the medulla, which is continuous 

 with the hilum. 



The sustentacular tissue forms a firm fibrous capsule envel- 

 oping the gland, which sends trabeccil&e or septa inward 

 toward the centre, dividing the gland into a number of radiat- 

 ing rounded lobules. Delicate retiform tissue, also a portion 

 of the sustentacular framework, fills the entire gland and 

 forms the basis of the lymphoid structures. 



The afferent lymph-vessels are a number of vessels or 

 branches which enter the gland at scattered points over the 

 periphery, emptying into the peripheral Ivmph-sinuses. 



The cortical portion of the gland is mainly made up of typical 

 lymphoid tissue, densely packed with lymphoid cells. It is 

 divided into lobules by the trabeculse, and each lobular mass 

 of lymphoid tissue is surrounded by a lymph-sinus. The 

 adenoid tissue in the outer or cortical part of the lobules 

 forms dense continuous masses ; but toward the centre it 

 breaks up into branches or columns of lymphoid tissue, called 

 lymph-cords, which project into the medulla and are sepa- 

 rated by the medullary lymph-sinuses and vessels. 



The lymph-sinuses are open channels and spaces in the 

 retiform tissue where the lymph is more free to flow than in 

 the dense adenoid tissue. They consist of the same open 

 reticulum which forms the basis of the lymphoid tissue; but 

 very few lymphoid cells are contained in the meshes, so that 

 the lymph is afforded free passage through the open network. 

 Into these sinuses the afferent and efferent lymph-vessels 

 freely open. 



These sinuses may be divided into two groups, the periph- 

 eral sinuses and the medullary sinuses. 



The peripheral lymph-sinuses surround the periphery of the 

 lymphoid tissue which makes up the various lobules, and the 

 afferent lymph vessels open into them. They consist of a 

 narrow space intervening between the capsule and trabeculse 

 and the dense lobular adenoid tissue. 



The medullary lymph-sinuses are located in the central por- 

 tion of the gland, and consist of branching open sinuses in- 



