THE SPLEEN. 79 



Transverse Section of a Cat's Spleen. EXAMINATION (L). Observe the serous covering 

 and also the fibrous capsule, thick and firmly adherent to the subjacent organ. Trace the 

 large coarse fibrous trabecula passing from its under surface into the organ, where they anas- 

 tomose and form a trabecular framework, which divides the organ into compartments of unequal 

 size, that communicate with each other, and are filled with the splenic pulp. The splenic 

 pulp consists of a large number of cells like lymph-corpuscles, mixed with yellow blood- 

 corpuscles. In it observe the rounded aggregations of lymph-corpuscles constituting Mal- 

 pigkian or splenic bodies. They are far more numerous relatively than in the human spleen, 

 and lie scattered irregularly in the pulp. They are not, as occasionally described, always 

 spherical bodies, but in reality are cord-like masses of adenoid tissue, like those of the lung, 

 developed on the walls of the arteries, usually more on one side of it than on the other, so that 

 one must look for a section of an artery in each mass ; and the position of the artery is eccentric. 

 Sometimes they are oval or spherical in shape. In the trabeculae search for sections of the 

 large branches of the splenic artery and vein, which run for a certain distance together in these 

 trabeculze. It is to be observed that the connective tissue which passes in on the blood-vessels 

 at the hilum becomes continuous with the trabeculse of the spleen itself. There is no lymph- 

 space between the trabeculae and the pulp. {Indicate the general arrangement in one half of 

 PI. XVIII., Fig. i.) 



(H). Observe the capsule, consisting of several layers of fibrous tissue intermixed with a 

 few elastic fibres and some non-striped muscle. Select a Malpighian body. Observe that it 

 is made up of leucocytes, lying in a meshwork of adenoid tissue. It has no definite wall, its 

 outer boundary is indicated by the leucocytes being more crowded together, and so it is 

 stained darker. It is a mass of adenoid tissue developed in the adventitia of an artery ; 

 therefore look for a section of an artery in it, cut either transversely or longitudinally. The 

 Pulp. Observe the colourless corpuscles, and note the admixture of a large number of 

 blood-corpuscles. The fine network of delicate fibrils in which they lie imbedded may be 

 observed. 



Human Spleen. (Logwood and Farrant's solution.) EXAMINATION (L). Observe the 

 capsule, trabecula?, arid splenic pulp. In the latter notice a mottled yellow and bluish ap- 

 pearance. The yellow streaks indicate the position of the blood-stream in the splenic pulp. 

 All the leucocytes are stained blue. Observe the relatively small number of splenic corpuscles, 

 which are usually ill-defined. The splenic corpuscles can usually be best seen in the spleen 

 of a young person, especially if the spleen be congested ; small masses of yellowish-brown 

 pigment may be found in the pulp. 



(H). A Malpighian corpuscle consists of a vascular mass of adenoid tissue, viz., a mesh- 

 work of adenoid reticulum loaded with leucocytes, many of which have two spherical nuclei 

 (PI. XVIII., Fig. 3). At their periphery they shade into the splenic pulp. The splenic pulp is 

 the most difficult part of the spleen to understand. Select a thin fragment at the margin of 

 the section, and observe the fine network of delicate fibrils crowded with leucocytes, and a 

 very large number of coloured blood-corpuscles. The latter give the pulp its yellow mottled 

 appearance. The framework or matrix of the pulp, when seen in sections, appears to consist of 

 fine fibrils, which form a network with very small meshes, varying in size from a coloured 

 blood-corpuscle to three or four times that size. It is probable, however, that it consists of nu- 

 cleated, branched, cell-plates, which anastomose so as to produce a honeycomb arrangement 

 (Klein). They not unfrequently contain (especially in the congested human spleen) small 

 masses of fine or coarse yellow pigment. It is important to observe that this fine meshwork 

 is directly continuous with the radicles of the veinlets. The cell-plates arrange themselves into 



