CHAP. XXXV.] CAPSULE OF THE SPLEEN. 509 



its internal surface is concave, and its external surface is in contact 

 with the diaphragm. The spleen lies in the left hypochondrium, 

 and extends upwards as high as the tenth rib, but when enlarged 

 reaches much higher, and increases upon the lower part of the 

 thoracic cavity. The spleen is of a dark red colour, highly vas- 

 cular, and of a soft pulpy consistence ; it varies much in size, 

 according to the state of general nutrition, and also at different 

 periods of the digestive process. The weight of the spleen com- 

 pared to that of the body at birth, is as 1 :350, in adult life 1 :320, 

 and in old age as 1 : 700. The following points have to be noticed 

 in considering the structure of the spleen: the capsule, the trabe- 

 cular tissue, the spleen pulp, or proper splenic parenchyma, and the 

 arrangement of the arteries, veins, nerves, and lymphatics. 



Capsule of the Spleen. The spleen is covered by a reflexion of 

 peritoneum, which extends to it from the fundus of the stomach, 

 and is called the gastrosplenic omen turn. The proper capsule of 

 the spleen is composed of white and yellow fibrous tissue, and per- 

 mits of considerable distension. It envelopes the organ entirely, 

 and is prolonged into the interior upon the vessels, which are 

 enclosed in sheaths composed of a structure closely resembling the 

 capsule of the organ. In man there is an absence of muscular 

 fibre-cells in the capsule; but in the dog and pig, and some other 

 mammalian animals, they are very numerous. 



Trabecular Tissue of the Spleen. If a section of a spleen be care- 

 fully washed under a stream of water, the dark-coloured soft pulpy 

 matter is removed, and a perfectly white and complicated fibrous 

 meshwork remains. The interspaces bounded by these trabeculse 

 vary much in size and form ; but they are all intersected by still 

 smaller trabeculse, and these smaller spaces by fibres visible only 

 by the aid of the microscope. The network thus formed, much 

 resembles that of the corpora cavernosa penis, and the fibres com- 

 posing it, are intimately connected with the fibrous capsule of the 

 organ, and also with the sheaths of the ^.245. 



vessels supplying it. The spaces or inter- 

 stices communicate freely with each other, 

 and in them is situated the pulpy tissue of 

 the spleen. 



The larger trabeculse, like the fibrous cap- 

 sule of the organ, are composed chiefly of 

 white fibrous tissue, with some fibres of the 

 yellow element. The smaller trabecula3 are ceiis from the trabecuiar tissue 

 composed of elongated spindle-shaped cells, 



