1078 THE ORGANS OF DIGESTION. 



The fibro-elastic coat forms the framework of the spleen. It invests the 

 exterior of the organ, and at the hilus is reflected inward upon the vessels in the 

 form of vaginae or sheaths. From these sheaths, as well as from the inner surface 

 of the fibro-elastic coat, numerous small fibrous bands, trabeculce (Fig. 688), are 



FIG. 688. Transverse section of the spleen, showing the trabecular tissue and the splenic vein and its branches. 



given off in all directions ; these, uniting, constitute the areolar framework of the 

 spleen. The framework of the spleen resembles, therefore, a sponge-like material, 

 consisting of a number of small spaces or areolce, formed by the trabeculse which 

 are given off from the inner surface of the capsule, or from the sheaths prolonged 

 inward on the blood-vessels. And in these spaces or areolae is contained 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 trabeculae 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. Miiller), but like them they pos- 

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



