THE SPLEEN. 951 



sheaths prolonged inward on the blood-vessels. In these spaces or areolse is con- 

 tained the splenic pulp. 



The proper coat, the sheaths of the vessels and the trabeculae, consist of a 

 dense mesh of white and yellow elastic fibrous tissues, the latter considerably pre- 

 dominating. It is owing to the presence of this tissue that the spleen possesses 

 a considerable amount of elasticity, which allows of the very great variations in 

 size that it presents under certain circumstances. In addition to these con- 

 stituents of this tunic, there is found in man a small amount of non-striped muscu- 

 lar fibre, and in some mammalia (e. g. dog, pig, and cat) a very considerable 

 amount, so that the trabeculse appear to consist chiefly of muscular tissue. It is 

 probably owing to this structure that the spleen exhibits, when acted upon by the 

 galvanic current, faint traces of contractility. 



The proper substance of the spleen or spleen-pulp is a soft mass of a dark 

 reddish-brown color, resembling grumous blood. When examined, by means of a 

 thin section, under a microscope, it is found to consist of a number of branching 

 cells and an intercellular substance. The cells are connective-tissue corpuscles, 

 and have been named the sustentacular or supporting cells of the pulp. The 

 processes of these branching cells communicate with each other, thus forming a 

 delicate reticulated tissue in the interior of the areolae formed by the trabeculae of 

 the capsule ; so that each primary space may be considered to be divided into a 

 number of smaller spaces by the junction of these processes of the branching 

 corpuscles. These secondary spaces contain blood, in which, however, the white 

 corpuscles are found to be in larger proportions than they are in ordinary blood. 

 The sustentacular cells are either small uni-nucleated or larger multi-nucleated 

 cells ; they do not become deeply stained with carmine, like the cells of the 

 Malpighian bodies, presently to be described (W. MUller), but like them they pos- 

 sess amoeboid movements (Cohnheim). In manv of them may be seen deep red 



FIG. 524. Transverse section of the human spleen, showing the distribution of the splenic artery and its 

 branches. 



or reddish-yellow granules of various sizes which present the characters of the 

 haematin of the blood. Sometimes, also, unchanged blood-disks are seen included 

 in these cells, but more frequently blood-disks are found which are altered both 

 in form and color. In fact, blood-corpuscles in all stages of disintegration may 

 be noticed to occur within them. Klein has recently pointed out that some- 

 times these cells in the young spleen contain a proliferating nucleus ; that is to 

 say, the nucleus is of large size, and presents a number of knob-like projections, 

 as if small nuclei were budding from it by a process of gemmation. This observa- 

 tion is of importance, as it may explain one possible source of the colorless blood- 

 corpuscles. 



The interspaces or areolee formed by the framework of the spleen are thus filled 



