CHAP, iv.] METABOLIC PROCESSES OF THE BODY. 739 



capillary network through the adenoid tissue, and at the circum- 

 ference open out into the labyrinth of the splenic reticulum. 

 These Malpighian corpuscles are so numerous that in a section of 

 a fresh normal spleen the dark red ground of the splenic substance 

 appears quite mottled by reason of the white dots. Hence no 

 inconsiderable portion of the blood reaching the spleen finds its way 

 into the meshes of the splenic reticulum after passing, through, 

 and, probably after acting upon, and being acted upon by, the 

 adenoid tissue of a Malpighian corpuscle. 



What is known as sago-spleen is so called because the 

 Malpighian corpuscles become enlarged and transparent, in 

 consequence of the leucocytes undergoing 'lardaceous' degene- 

 ration ; the same change may also affect the adenoid tissue of the 

 small arteries and may even spread to the spleen-pulp. 



473. The nerves of the spleen which pass into the organ at 

 the hilus with the blood vessels are derived from the solar plexus. 

 They consist chiefly of non-medullated fibres mingled with which 

 are. a few medullated fibres. Their terminations have not been as 

 yet exactly made out, but while many presumably are distributed 

 to the blood vessels there can be little doubt that some end in the 

 capsule and trabeculse, at least where these contain muscular tissue, 

 and thus bring the contractions of these structures under the 

 guidance of the central nervous system. 



The centripetal course of the fibres of these splenic nerves has 

 not yet been made out definitely ; we may perhaps safely conclude 

 that the majority are derived, like the fibres distributed to the 

 neighbouring abdominal organs, from the dorsal spinal cord. That 

 the vagus also contributes fibres is very probable. 



474. When the so-called spleen pulp is examined under the 

 microscope, it is found to consist, besides the branched cells and 

 fibres constituting the reticulum, of cells which may be described 

 as partly red corpuscles and partly white corpuscles or leucocytes. 

 W T e spoke of the meshes of the reticulum as being filled with 

 blood; but it is obvious that the corpuscles of the blood must 

 move less readily through the labyrinth than does the fluid plasma, 

 and that hence a concentration of the corpuscles as compared with 

 the plasma must take place in the meshes. The contents of the 

 meshes cannot, property speaking, be called blood, but are rather 

 aggregations of corpuscles with a relatively small quantity of 

 fluid. 



The white corpuscles or leucocytes are very various. Some are 

 small, like the leucocytes of a lymphatic gland, the cell-substance 

 being scanty relatively to the nucleus. Others are indistinguish- 

 able from the ordinary white corpuscles of the blood. Others 

 again are large, twice as large as an ordinary white corpuscle or 

 even larger than this, possess more than one nucleus, and contain 

 in their cell-substance numerous refractive, pale yellow or colour- 

 less granules. Some of these larger forms, which like the others 



472 



