SPLEEN. 



[ 720 ] 



SPLEEN. 



peritoneum, except at the hilus, where the 

 vessels are connected with it. 



Beneath the peritoneal tunic is a thin, 

 semitransparent, firm, fibrous coat, which at 

 the hilus accompanies the vessels, and forms 

 sheaths around them. 



The spleen is traversed hy fibrous bands 

 or trabeculse (fig. 674), which arise from 

 the inner surface of the fibrous coat and 

 from the outer surface of the vascular 

 sheaths, and, being- connected with each 

 other, form a number of irregular meshes 

 or areolae, in which are situated the splenic 

 corpuscles and the spleen-pulp. In reptiles 

 they form stellate expansions, their connec- 

 tive tissue becoming infiltrated with lymph- 

 corpuscles; and the connective tissue in 

 this modified form occupies all the inter- 

 spaces of the proper parenchyma of the 

 organ. 



The fibrous coat and the trabeculse consist 

 of ordinary connective tissue, with mostly 

 parallel fibres, traversed by networks of fine 

 elastic fibres, which become continuous with 

 the coats of the veins. In certain animals, 

 as the dog, cat, pig, &e,, the fibrous coats 

 and trabeculse contain also unstriped mus- 

 cidar fibres. These do not occur in man, 

 unless they are represented in the micro- 

 Fig. 677. 



scopic trabeculse by pecidiar wavy fibres, 

 about 1-500" in length, with lateral or 

 stalked nuclei (fig. 67o). Some of these 

 are found enclosed in cells (fig. 676), from 

 which they become liberated by the action 

 of water. 



The splenic or Malpighian corpuscles 

 (fig. 677) are white rounded bodies, imbed- 

 ded in the spleen-pulp, and attached to the 

 smallest arteries. They vary in size from 

 1-120 to 1-36", and cannot always be de- 

 tected. They are either placed upon the 

 sides of the arterial branch, or situated in 

 the angles of their bifurcation. 



The splenic corpuscles consist of an enve- 

 loping membrane (fig. 678 a) composed of 

 connective tissue with fine reticular elastic 

 fibres, and derived from the arterial sheath. 

 They are traversed by capillaries and filled 

 with a tenacious grey parenchyma. The 

 parenchyma consists of cells 1-3000" in 

 diameter, containing one or two nuclei, and 

 free nuclei (fig. 104, p. 138). Sometimes 

 the cells contain globules of fat or blood- 

 corpuscles ; and occasionally free blood-cor- 

 puscles are met with. When the splenic 

 corpuscles undergo amyloid degeneration, 

 they produce the so-called sago-spleen. 



"The splenic pulp forms a soft reddish 



Fig. 678. 



Pig. 677. Portion of a smaO artery from the spleen of a dog, with one of the branches covered witli Malpighian 

 bodies. Magnifii'd 10 diameters. 



Fig. 678. Malpighian corpuscle from the spleen of an ox. «, wall of the corpuscle; b, contents; e, wall of the 

 artery upon which it is situated ; d, its sheath. Magnified 150 diameters^ 



