STRUCTURE AND FUNCTIONS OF THE SPLEEN. 287 



which appears to be comparable to the elementary vesicles of other 

 glands, before they have acquired an outlet by the rupture of their 

 walls ( T18). Whatever may be the function of these bodies, it is pro- 

 bable that it must be completed by the rupture of the capsules and the 

 discharge of their contents ; and that new corpuscles are continually in 

 course of development. The true splenic parenchyma consists in great 

 part of cells which correspond in appearance with those of the Mal- 

 pighian corpuscles ; but in addition to these, there are cells which bear 

 a strong likeness to the colourless * granule-cells' of the blood ( 217), 

 and others which resemble young red-corpuscles. These elements, also, 

 present indications of being in a state of continual development and 

 degeneration; and form small irregular groups of various sizes, which 

 are clustered especially on the sheaths of the vessels, the trabecular 

 partitions, and the exterior of the Malpighian capsules. A considerable 

 part of the contents of the splenic areolae has been found by Prof. 

 Kolliker to consist of blood-corpuscles in various stages of degenerative 

 metamorphosis. These are aggregated in small masses, each of which 

 acquires an investing membrane, that may contain from one to twenty 

 corpuscles ; and the blood-cells gradually dimmish in size, and undergo 

 a transition into pigment-granules ; so that the containing cells are 

 converted into pigmentary granule-cells, which at last, by a gradual 

 loss of colour of the granules, become quite pale. Such cells are found 

 in the blood drawn from the splenic vein, the vena portse, and the in- 

 ferior cava ; and occasionally in that of other veins. These curious 

 collections of degenerating blood-corpuscles, however, are not peculiar 

 to the spleen, for they have been found by Prof. Kolliker in other parts, 

 such as the substance of the muscles. - 



507. In regard to the functions of the Spleen, great uncertainty still 

 exists. It appears from the foregoing account of its structure, that it 

 may be regarded as an organ of duplex character, and probably of 

 double function. In the Ruminants, the cavernous dilatations of the 

 veins enable it to hold, upon occasion, a large quantity of blood ; and 

 their walls are so elastic, that their cavities may be greatly distended 

 with a very moderate force ; the Spleen of the sheep, which weighs 

 about 4 oz., being easily made to contain about 30 oz. of water. This 

 peculiar distensibility evidently points to the Spleen, as a kind of 

 reservoir, connected with the Portal circulation, for the purpose of 

 relieving the portal vessels from undue pressure or distension, under a 

 great variety of circumstances. The portal system is well known to 

 be destitute of valves, so that the splenic vein communicates freely with 

 the whole of it ; and thus, if any obstruction exists to the flow of blood 

 through the liver, or any peculiar pressure elsewhere prevents the 

 mesenteric veins from dilating to their full extent, the general circula- 

 tion is not disturbed, the Spleen affording a kind of safety-valve. That 

 any cause of congestion of the Portal system peculiarly affects the 

 Spleen, has been proved by experiment ; for, after the portal vein has 

 been tied, the spleen of an animal that previously weighed only 2 oz., 

 has been found to increase to 20 oz. Again, the Spleen appears t( 

 serve as a reservoir, into which superfluous blood may be carried, during 

 the digestive process. When the alimentary canal is distended with 



