Page:Proceedings of the Royal Society of London Vol 4.djvu/483

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Henry Wollaston Blake, Esq., and James Heygate, M.D., were balloted for and duly elected Fellows of the Society.

The following papers were read, viz. —

1. " On the general and minute Structure of the Spleen in Man and other Animals." By William Julian Evans, M.D. Communicated by P. M. Roget, M.D., Sec. R.S,

After adverting briefly to the discordant opinions of Malpighi, Ruysch, and others regarding the structure of the spleen, the author proceeds to detail the results of the investigations on this subject, in which he has been for many years engaged. According to his ana- lysis, the following are the component parts of this organ : — first, a reticulated fibro-elastic tissue ; secondly, a pulpy parenchyma, con- taining the Malpighian glands and the splenic corpuscles ; thirdly, distinct cellular bodies ; fouiihly, the usual apparatus of arteries, veins, lymphatics and nerves ; fifthly, certain fluids ; and lastly, the membranes or tunics by which it is invested.

He describes the cells of the spleen as being formed of a lining membrane, continued from that of the splenic vein, and strengthened by filaments of the fibro-elastic tissu.e. The splenic vein communi- cates with these cells, at first by round foramina, then by extensive slits resembling lacerations ; and it ultimately loses itself entirely in the cells. The cells themselves communicate freely with one another, and also with the veins of the parenchyma ; and may therefore be considered as in some measure continuations of the veins. This structure constitutes a multilocular reservoir of great extensibility, and possessing great elastic contractility ; properties, however, which exist in a much less degree in the human spleen than in that of her- bivorous animals; in which animals the cellated structure itself is much more conspicuous, and predominates over the parenchymatous portion. As the splenic artery has no immediate communication with the cells, these latter may be filled much more readily by in- jection from the vein than from the artery. In the ordinary state of the circulation, the blood, which has passed into the cells from the veins, is pressed into the branches of the splenic veins by a force de- rived from the elasticity of the fibro-elastic tissue which surrounds the cavities of the cells, thus constituting a vis-a-tergo, which con- tributes to propel the blood onwards in its jeirculation through the liver. Should there arise, however, any obstructing cause which the resilience of the spleen is unable to overcome, a regurgitation must take place, leading to a congestion both in the mesenteric and splenic veins. The spleen may thus serve as a receptacle for the blood of the abdominal circulation during any temporary check to its free passage into the vena cava; a purpose which is more fully answered in herbivorous animals in whom the abdominal circulation is more