VASCULAR GLANDS THE SPLEEN. 219 



form a network that extends through the entire organ, becoming connected 

 also with the fibrous sheaths of the vessels which penetrate it. These bands 

 are partly muscular in those animals which have muscular fibres in the ex- 

 ternal envelope ; but elsewhere they are simply fibrous. The spaces left by 

 their intersection, which are by no means regular as to either form or size, 

 are occupied by the splenic corpuscles and splenic parenchyma. 



ii. Of the Arteries of the Spleen, it is chiefly to be observed that their 

 branches form no anastomoses, but subdivide and ramify like the branches 

 of a tree, with the Malpighian corpuscles attached to them as fruit (Fig. 93). 

 Beyond their connection with these, however, they enter the general mass of 

 the splenic parenchyma ; and here each twig subdivides into a tuft of arteri- 

 oles still more minute, which either pass directly into capillary veins (Bill- 

 roth) or again subdivide into the true capillaries. At their entrance into 

 the hilus of the organ, the arteries receive a sheath from the capsule com- 

 posed of fibrillar connective tissue, with numerous elastic fibres, and a mod- 

 erate proportion of cell elements. Where the arteries separate from the 

 veins, and are not more than 7 '- 5 th to y^th of an inch in diameter, the 

 sheaths become much looser and converted into a cytogenous tissue. The 

 Capillaries, bounded only by their very thin walls, pass in every direction 

 through the spleen-pulp, both in the general mass of the organ, and also in 

 the interior of the Malpighian corpuscles. But it is affirmed by Mr. Gray, 

 with whom Stieda and W. Miiller, and still more recently Stoff and Hasse, 1 

 agree, that in the Spleen of Man and of many other animals, the walls of 

 the capillaries frequently disappear, and that the blood, in passing from the 

 minutest arteries to the minutest veins, moves in great part through lacunae., 

 or mere channels in the pulp-tissue. Of the Veins, the idea has been gen- 

 erally entertained, that they are dilated into cavernous spaces or sinuses; 

 but this, though true of many of the lower Mammalia, especially of rumi- 

 nants and diving animals, is the case to only a very limited extent in Man. 

 Their mode of ramification closely resembles that of the arteries; and they 

 are unprovided with valves. 



in. The Parenchyma of the Spleen essentially consists of cells in various 

 stages of evolution, imbedded in a granular plasma (the periplast of Hux- 

 ley) ; thus corresponding in every essential particular with the contents of 

 the Peyerian and absorbent glandulse ( 156), and giving evidence, as they 

 do, of being in a state of rapid developmental change. The amount of this 

 colorless parenchyma is stated by Mr. Gray to undergo a marked increase 

 towards the end of the digestive process, when a large quantity of new ali- 

 mentary material is being introduced into the sanguiferous current; whilst, 

 in the intervals of this operation, it undergoes a gradual diminution. The 

 peculiar Splenic Corpuscles, or " Malpighian bodies of the Spleen," are 

 whitish spherical bodies, which are connected with the smaller arteries by 

 short peduncles, like grapes with their fruit-stalks, or are sessile upon their 

 sheaths (Fig. 93). Their diameter usually varies between one-third and 

 one-sixth of a line ; smaller bodies, however, are met with, which appear to 

 be Malpighian corpuscles in an earlier stage of evolution. The boundary of 

 each is an indistinctly fibrous membrane, which appears to be partly formed 

 by the metamorphosis of the external cells of its contained parenchyma, and 

 to be partly derived from the fibrous coat of the artery to which it is 

 attached. 2 And its contents correspond, in every essential particular, with 



1 Centralblatt, 1872, p. 753. 



2 It has been commonly supposed that the Malpisjhian corpuscles are invested by 

 a distinct limitary membrane, like the ac.ini of ordinary Glands; but such, from the 

 observations of Wharton Jones and Huxley, would clearly seem to be not the case. 



