122 NORMAL HISTOLOGY. 



The trabeculae all along their course give off numerous ramifi- 

 cations which break up into the delicate reticulum constituting the 

 supporting framework in whose meshes the lymphoid cells are 

 held. 



The blood-vessels supplying the lymphatic glands are arranged 

 as two groups : the one set gains entrance at the periphery and is 

 distributed principally to the capsule and larger trabeculae ; the other 

 group enters at the hilum, the majority of the arterial branches pass- 

 ing directly into the lymphoid tissue. The nerves include both 

 the medullated and the pale fibres. 



In certain localities, especially in the prevertebral retroperitoneal 

 and cervical regions, in the vicinity of the abdominal aorta, vena 

 cava, adrenal and renal vessels, along the brim of the pelvis and in 

 the root of the mesentery, are found minute organs known as hem- 

 olymph glands (Warthin). They lie embedded within the fat 

 and connective tissue and are usually the size of a mustard-seed or 

 pea ; exceptionally they are larger. The hemolymph glands are 

 lymph-nodules modified by the presence of blood-spaces and the 

 slight development or absence of the lymph-sinuses. The blood- 

 spaces often include a peripheral blood-sinus with irregular cen- 

 tral extensions, the lymphoid tissue being correspondingly reduced 

 to trabeculae surrounded by the vascular channels. All degrees 

 of development of the blood-spaces exist, from the type of the 

 ordinary lymph-nodule on the one hand to that of the spleen on 

 the other. Warthin subdivides the hemolymph glands into two 

 groups, the splenolymph and the marrowlymph glands, which 

 he regards as transitional forms standing between the lymphatic 

 nodule on the one side and the spleen and the lymphoid marrow 

 respectively on the other. 



THE SPLEEN. 



The spleen may be regarded as a specialized compound lymphatic 

 gland, modified by the arrangement of its blood-supply. The organ 

 is invested by a firm capsule, composed of a dense felt-work of 

 bundles of fibrous tissue, with which are mixed numerous elastic 

 fibres. The outer surface of the capsule, with the exception of a 

 limited area, is covered by the serous coat of the peritoneum, the 

 union between the two being very intimate. 



On the inner surface the capsule is continuous with numerous 

 prolongations, the trabeculae. These penetrate deeply into the 

 interior from all sides, and by the free union of their processes form 

 <a spongy connective-tissue framework throughout the organ, 

 enclosing an elaborate system of intercommunicating spaces occupied 

 by the lymphoid tissue. 



