THE LYMPHATIC SYSTEM. 



123 



In certain animals (dog, cat, hog) the capsule contains bundles of 

 involuntary muscle ; these are only exceptionally present in man. 



FIG. 148. 



FIG. 149. 



FIG. 150. 



Section of spleen of dog, showing general structure : a, capsule, from which trabeculae extend ; sec- 

 tions of these latter are seen in several places, as at d ; b, tissue of splenic pulp ; c, c, Malpighian 

 corpuscles ; e, sections of blood-vessels. 



Likewise, bundles of muscular tissue are constituents of the trabeculae 

 in many mammals, including man to a limited degree ; the muscle- 

 cells are distin- 

 guishable from 

 the surrounding 

 connective tissue 

 by their rod- 

 shaped nuclei. 

 The stoutest tra- 

 beculae are found 

 at the hilum, 

 which corre- 

 sponds to the 

 position at which 

 the larger blood- 

 vessels enter and 

 leave the organ. 

 The lymphoid 

 tissue filling the 

 intertrabecular 

 spaces exists in 

 two forms as the loose adenoid tissue which, together with the 



Section of human spleen, showing 

 trabeculae (a) and fibrous reticulum (b) 

 continued into the surrounding splenic 

 pulp ; c, lymphoid cells 



Transverse section of large 

 trabecula of human spleen : a, 

 fibrous tissue, containing a few 

 groups of plane muscle-cells (b) ; 

 c, extension of trabecula into 

 fibrous reticulum ; d, lymph- 

 corpuscles. 



