

i 



THE SPLEEN 1283 



and below this with the tail of the pancreas. It presents near its medial border a 

 long fissure, termed the hilum. This is pierced by several irregular apertures, for 

 the entrance and exit of vessels and nerves. 



The renal surface (fades renalis) is directed medialward and downward. It is 

 somewhat flattened, is considerably narrower than the gastric surface, and is in 

 relation with the upper part of the anterior surface of the left kidney and occasion- 

 ally with the left suprarenal gland. 



The superior extremity (extremitas superior') is directed toward the vertebral 

 column, where it lies on a level with the eleventh thoracic vertebra. The lower 

 extremity or colic surface (extremitas inferior] is flat, triangular in shape, and rests 

 upon the left flexure of the colon and the phrenicocolic ligament, and is generally 

 in contact with the tail of the pancreas. The anterior border (margo anterior] is free, 

 sharp, and thin, and is often notched, especially below; it separates the diaphragmatic 

 from the gastric surface. The posterior border (margo posterior'), more rounded and 

 blunter than the anterior, separates the renal from the diaphragmatic surface; 

 it corresponds to the lower border of the eleventh rib and lies between the diaphragm 

 and left kidney. The intermediate margin is the ridge which separates the renal 

 and gastric surfaces. The inferior border (internal border) separates the diaphrag- 

 matic from the colic surface. 



The spleen is almost entirely surrounded by peritoneum, which is firmly adherent 

 to its capsule. It is held in position by two folds of this membrane. One, the 

 phrenicolienal ligament, is derived from the peritoneum, where the wall of the general 

 peritoneal cavity comes into contact with the omental bursa between the left kidney 

 and the spleen; the lienal vessels pass between its two layers (Fig. 1039). The other 

 fold, the gastrolienal ligament, is also formed of two layers, derived from the 

 general cavity and the omental respectively, where they meet between the spleen 

 and stomach (Fig. 1039) ; the short gastric and left gastroepiploic branches of the 

 lienal artery run between its two layers. The lower end of the spleen is supported 

 by the phrenicocolic ligament (see page 1155). 



The size and weight of the spleen are liable to very extreme variations at different 

 periods of life, in different individuals, and in the same individual under different 

 conditions. In the adult it is usually about 12 cm. in length, 7 cm. in breadth, and 

 3 or 4 cm. in thickness, and weighs about 200 grams. At birth its weight, in pro- 

 portion to the entire body, is almost equal to what is observed in the adult, being 

 as 1 to 350; while in the adult it varies from 1 to 320 and 400. In old age the organ 

 not only diminishes in weight, but decreases considerably in proportion to the entire 

 body, being as 1 to 700. The size of the spleen is increased during and after diges- 

 tion, and varies according to the state of nutrition of the body, being large in 

 highly fed, and small in starved animals. In malarial fever it becomes much 

 enlarged, weighing occasionally as much as 9 kilos. 



Frequently in the neighborhood of the spleen, and especially in the gastrolienal 

 ligament and greater omentum, small nodules of splenic tissue may be found, either 

 isolated or connected to the spleen by thin bands of splenic tissue. They are known 

 as accessory spleens (lien accessories; supernumerary spleen). They vary in size 

 from that of a pea to that of a plum. 



Structure. The spleen is invested by two coats: an external serous and an internal fibro- 

 elastic coat. 



The external or serous coat (tunica serosa) is derived from the peritoneum ; it is thin, smooth, 

 and in the human subject intimately adherent to the fibroelastic coat. It invests the entire 

 organ, except at the hilum and along the lines of reflection of the phrenicolienal and gastrolienal 

 ligaments. 



The fibroelastic coat (tunica albuginea} invests the organ, and at the hilum is reflected inward 

 upon the vessels in the form of sheaths. From these sheaths, as well as from the inner surface 

 of the fibroelastic coat, numerous small fibrous bands, trabeculae (Fig. 1189), are given off in all 

 directions; these uniting, constitute the frame-work of the spleen. The spleen therefore consists 



