SPLEEN, THE, is the largest and most important of the so called ductless glands, whose chief object is supposed to be to restore to the circulation any substances that may have been withdrawn from it. It is of an oblong flattened form, soft, of very brit tle consistence, highly vascular, of a dark bluish-red color, and situated on the left hypochondriac region, with its interior slightly concave surface embracing the cardiac end of the stomach and the tail • of the pancreas. (See the figure in the article PAN CREAS.) It is invested by an external or scrolls coat, derived from the peritoneum, and an internal fibrous elastic coat. Mr. Gray, who wrote the Astley- Cooper prize essay, On the Sructure and Use of the Spleen, states that the size and weight of this organ are liable to very extreme variations at different periods of life, in differentindividuals, and in the same individual under different conditions. In the adult, in whom it attains its greatest size, it is usually about 5 in. in length, 3 or 4 in breadth, and an inch or an inch and a half in thickness, and weighs about 7 ounces. At birth its weight in proportion to that of the entire body is as 1 to 350, which is nearly the same ratio as in the adult; while in old age the organ decreases in weight, the ratio being as 1 to 700. The size of the spleen is increased during and after digestion, and is large in highly fed, and small in starved animals. In intermittent fevers and leucocythemia it is much enlarged, weighing occasionally from 18 to 20 lbs., and constituting what is popularly known as the ague-cake On cutting into the spleen a section of it shows the presence of numerous small fibrous bands termed trab6cula, united at numerous points with one another, and run in all directions. The parenchyma, or proper substance of the spleen, occupies the interspaces of the above described areolar frameWork, and is a soft pulpy mass of a dark reddish-brown color, consisting of colorless and colored elements. The colorless elements are described by Gray as consisting of granular matter, of nuclei about the size of the red blood-disks, and a few nucleated vesicles; and asconstituting•ne-half or two thirds of the whole substance of the pulp in well-nourished animals, while they dimin ish in number, and sometimes altogether disappear in starved animals. The colored de
scents consist of red blood-disks and of colored corpuscles either free or included in cells; sometimes enlarged blood-disks are seen included in a cell, but more frequently the enclosed disks are altered in form and color, as if undergoing retrograde meta morphoses. Besides these, numerous deep-red, or reddish-yellow, or black corpuscles and crystals, closely allied to the hmmatin of the blood, are seen diffused through the pulp substance. .
The venous blood of the spleen is carried away by the splenic vein, which con tributes to form the great portal venous system, distributed through the liver; while arterial blood is supplied by the splenic artery, the largest branch of the eceliac. axis. The branches of this artery subdivide and ramify like the branches of a tree, with the vadpIlohian or splenic corpuscles attached to them like fruit. These spicule corpuscles, originally discovered by Malpighi. are whitish spherical bodies, which are either con nected with the smaller arterial branches by short pellicles, or are sessile upon their sheaths. They vary considerably in size and number, their diameter usually ranging from one-third to one-sixth of aline. Each consists of a membranous capsule, homo geneous in structure, and formed by a prolongation from the sheath of the artery. The blood-vessels ramifying on the surface of a corpuscle consist of the larger branches of the artery with which it is connected, of venous branches, and of a delicate capillary plexus. From this arrangement of the vessels, it may be inferred that active changes are carried on in the contents of these corpuscles, which consist of a soft, white, semi fluid substance, made up of granular matter, nuclei similar to those found in the pulp, and a few nucleated cells. These splenic corpuscles are much more distinct in early life than subsequently, and are much smaller in man than in most mammals. They, how e'er, bear a remarkable relation to the general state of nutrition, being much the great est in well-fed animals, especially in the early periods of the digestion of albuminous food; while they diminish extremely in ill-fed animals, and in those that have been starved, they disappear altogether.