Aldred Scott Warthin 71 



trating blood-vessels. Occasionally the blood-spaces and vessels in the 

 capsule are so numerous as to give it the cavernous structure so fre- 

 quently seen in the capsule of these glands in the steer; but on the 

 vrhole the splenolymph glands of man are distinguished from those of 

 the lower animals by the less vascular structure of the capsule. From 

 the external capsule trabeculse of similar tissues run into the gland 

 dividing it into irregular lobules. Accompanying the trabeculas are the 

 communicating blood-sinuses and between them lies the lymphoid 

 tissue. 



Blood-sinuses. — Immediately beneath the external capsule there is a 

 blood-sinus which sometimes extends entirely around the periphery 

 of the gland, but more frequently only for portions of the way, being 

 frequently interrupted by masses of lymphoid tissue which reach to 

 the external capsule. In the great majority of cases this sinus is much 

 smaller and less prominent than in the hemolymph glands of the steer 

 and sheep. Glands are, however, occasionally seen in man with the 

 peripheral sinus dilated and 'containing as much blood as in any gland 

 from these animals. From the peripheral sinus branches pass in with 

 the trabeculae toward the centre of the gland or toward its hilum, 

 increasing in size and becoming confluent towards these points until 

 they are often very large and prominent. These radiating sinuses fre- 

 quently commiinicate with each other, and so divide the lymphoid tis- 

 sue into irregularly-shaped islands apparently surrounded on all sides 

 by a blood-sinus. Serial sections, however, show that these islands 

 are not entirely cut off from each other in the majority of cases, but 

 at some point or other are connected by an isthmus of lymphoid tissue 

 of varying size. The number and size of the blood-sinuses as well as 

 their general arrangement vary greatly, so that scarcely any two glands 

 exactly resemble each other in these respects. 



The lumen of the peripheral as well as of the communicating and 

 central sinuses is traversed by a coarse reticulum through the meshes 

 of which the blood circulates. The amount of this reticulum and the 

 size of its meshes vary in different 'glands; frequently the central sin- 

 uses are open, possessing but a scanty reticulum or none at all. The 

 reticulum of the sinuses is probably lined throughout with flattened 

 endothelium, but it is sometimes difficult or impossible to make this 

 out, so that the blood appears to be in direct contact with fibres of the 

 reticulum. A wide sinus is often abruptly narrowed by a constriction 

 of coarser reticulum suggesting a valve-like arrangement, but this 

 point is yet to be worked out. The course of the sinuses is clearly shown 

 in sections by the lighter staining nuclei of the reticulum in contrast 



