474 



SECRETION. 



ure are important in their relation to certain physiological changes in the size of the 

 spleen. Its contractility may be easily demonstrated in the dog by the application of a 

 galvanic current to the nerves as they enter at the hilum. This is followed by a prompt 

 and energetic contraction of the organ. Contractions may be produced, though they 

 are much more feeble, by applying the current directly to the spleen. 



The substance of the spleen is soft and friable; and a portion of it, the spleen-pulp, 

 may be easily pressed out, or even washed away by a current of water. Aside from the 

 vessels and nerves, it presents for study: 1. An arrangement of fibrous bands, or tra- 

 beculse, by which it is divided into innumerable communicating cellular interspaces. 2. 

 Closed vesicles (Malpighian bodies), attached to the walls of the blood-vessels. 3. A soft, 

 reddish substance, containing numerous cells and free nuclei, called the spleen-pulp. 



Fibrous Structure of the Spleen (Trabeculce). From the internal face of the investing 

 membrane of the spleen and from the fibrous sheath of the vessels (capsule of Malpighi), 

 are numerous bands, or trabeculaa, which, by their interlacement, divide the substance 

 of the organ into irregularly-shaped, communicating cavities. These bands are from ^V 

 to -^ of an inch broad, and are composed, like the proper coat, of ordinary fibrous tissue 

 with elastic fibres and probably a few smooth muscular fibres. They pass off from the 

 capsule of Malpighi and the fibrous coat at right angles, very soon branch, interlace, and 

 unite with each other, becoming smaller and smaller, until they measure from -^ to -^ 

 of an inch. As we should expect from the very variable size of the trabeculse, the dimen- 

 sions as well as the form of the cavities are exceedingly irregular. This fibrous net-work 

 serves as a skeleton or a support for the softer and more delicate parts. 



Malpighian Bodies. In the very elabo- 

 rate work on the spleen, by Malpighi, is a full 

 account of the closed follicles, which have 

 since been called the Malpighian bodies. 

 They are sometimes called the splenic cor- 

 puscles or glands. They are in the form of 

 rounded or slightly ovoid corpuscles, about 

 -jV of an inch in diameter, consisting of a deli- 

 cate membrane, generally homogeneous, but 

 sometimes faintly striated, with semifluid con- 

 tents. In their form, size, and structure, 

 they bear a close resemblance to the closed 

 follicles of the small intestine. The investing 

 membrane has no epithelial lining, and the 

 contents consist of an albuminoid liquid, with 

 numerous small, nucleated cells and a few 

 free nuclei. The cells measure from ^V^r to. 

 2-5*5-5- f an i n h i n diameter. Both the cells 

 and the free nuclei of the splenic corpuscles 

 bear a close resemblance to cells and nuclei 

 found in the spleen _ pulp . The corpuscles are 



surrounded by blood-vessels, which send 

 branches into the interior, to form a delicate 

 capillary plexus. 



The number of the Malpighian corpuscles in a spleen of ordinary size has been esti- 

 mated by Sappey at about ten thousand. They are readily made out in the ox and 

 sheep but are frequently not to be discovered in the human subject. In about forty 

 examinations, in man, Sappey found them in only four; but in these they presented the 

 same characters as in the ox and the sheep, and resisted decomposition for twelve days, 



FIG. 



of the Q** of the pig. 



a, an artery, with its branches (b, fy ; c, c, c, Malpighian 

 bodies. 



