THE SPLEEN. 147 



and of peculiar cells of the parenchyma. In Man and in 

 Animals the occurrence of extravasated blood, in manifold 

 stages of metamorphosis, is so frequent, that it may be almost 

 regarded as a normal constituent. According to its amount 

 and to the distension of the blood-vessels, the pulp appears 

 sometimes of a brighter, sometimes of a darker blood-red ; be- 

 sides which, however, it must be noted that the pulp has also its 

 own proper red colouring matter. 



The fibres of the pulp are of two kinds. Firstly, there are 

 microscopic trabecule, answering completely to those visible 

 with the naked eye and possessing the same structure, except 

 that in many Mammals they contain more smooth muscles, 

 or are even entirely composed of them. As a general rule, 

 their diameter varies between 0*005 'and 001'"; in quantity 

 they differ in different animals and in different parts of the 

 spleen. In Man I find them to be more rare and broader than 

 in other Mammals, and perfectly identical in their structure 

 with the larger trabecules. Other fibres which occur in the 

 pulp are plainly the terminations of the vascular sheaths. They 

 are very numerous, and usually have the appearance of delicate, 

 indistinct, fibrous membranes, without any elastic element, 

 which appear to connect the capillaries, and are, perhaps, con- 

 tinuous with the finest trabecules. 



The cells of the pulp, or parenchyma-cells of the spleen, round 

 cells of 0*003 — 0-005'", with single nuclei, are for the most part 

 so similar to those in the Malpighian corpuscles, that it is un- 

 necessary to enter upon a more minute description of them; 

 intermingled with them, and, indeed, in larger quantities than 

 in the Malpighian corpuscles, we find free nuclei. Besides 

 these, a few other elements may he met with : — 1. pale round 

 bodies, with a homogeneous aspect, somewhat larger than the 

 corpuscles of the blood, which appear either as free nuclei, or 

 as homogeneous nuclei, closely surrounded by a delicate invest- 

 ment; 2. larger cells, up to 001'" in diameter — both of the 

 completely pale kind, with one or two nuclei, and also what I 

 have called colourless granule -cells — that is, cells with more 

 or fewer colourless, dark fat-granules. Each of these elements 

 exists in the splenic corpuscles also, but never to so great 

 an amount. The quantity of the different kinds of paren- 

 chyma cells and of free nuclei in the pulp, is so considerable, 



