THE DUCTLESS GLANDS 



inches in length. It is of an oblong, flattened, tetrahedral form, soft, of very 

 friable consistence, highly vascular, and of a dark-purplish color. 



Relations. The external or phrenic surface (fades diphragmatica) is convex, smooth, and 

 is directed upward, backward, and to the left, except at its upper end, where it is directed slightly 

 inward. It is in relation with the under surface of the Diaphragm, which separates it from 

 the ninth, tenth, and eleventh ribs of the left side, and the intervening lower border of the left 

 lung and pleura. 



The internal surface is concave, and divided by a ridge into an anterior or gastric, and a 

 posterior or renal portion. 



Tae gastric surface (fades gastrica), which is directed forward and inward, is broad and 

 concave, and is in contact with the posterior wall of the fundus of the stomach; and below this 

 with the tail of the pancreas. It presents near its inner border a long fissure, termed the hilum 

 (hilus lienis), in which are several irregular apertures, for the entrance and exit of vessels and 

 nerves. 



The renal surface (fades renalis) is directed inward and downward. It is somewhat flattened, 

 is considerably narrower than the gastric surface, and is in relation with the upper part of the 

 outer surface of the left kidney and occasionally with the left suprarenal gland. 



The upper end of the spleen (extremitas superior') is directed inward, toward the vertebral 

 column, where it lies on a level with the eleventh thoracic vertebra, within one and one-half to 

 two inches of the midline. The lower end (extremitas inferior), sometimes termed the basal 

 surface, is flat, triangular in shape, and rests upon the splenic flexure of the colon and the 

 phrenocolic 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 sepa- 

 rates the phrenic surface from the gastric surface. The posterior border (margo posterior), 

 more rounded and blunter than the anterior, separates the renal from the phrenic surface; 

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

 left kidney. The internal border, or intermediate margin, is the ridge which separates the 

 renal and gastric portions of the internal surface. 



The spleen, with the exception of its hilum, is completely invested with peritoneum, which 

 is firmly adherent to the capsule of the organ. Two folds of peritoneal tissue the lienorenal 

 ligament and the gastrosplenic omentum serve to hold the organ in position. The lienorenal 

 ligament (Figs. 982 and 985) is derived from the layers of the peritoneum forming the greater 

 and lesser sacs where they come into contact between the left kidney and the spleen. Between 

 these two layers the splenic vessels pass. The gastrosplenic omentum (ligamentum gastro- 

 lienale) is also formed of two layers, derived from the greater and lesser sacs, respectively, where 

 they meet between the spleen and the fundus of the stomach (Fig. 985). Between these two 

 layers run the vasa brevia and the left gastroepiploic branches of the splenic artery and vein. 

 The spleen is also supported by the phrenocolic ligament (see p. 1265). 



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, in whom it attains its greatest size, it is usually about five inches in length, three inches 

 in breadth, and an inch or an inch and a quarter in thickness, and weighs about six and one- 

 half ounces. At birth, its weight, in proportion 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 to 1 to 400. 

 In old age the organ not only decreases 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 

 digestion, and varies considerably according to the state of nutrition of the body, being large 

 in well-fed, and small in starved animals. In intermittent and other fevers it becomes much 

 enlarged, weighing occasionally from eighteen to twenty pounds. 



Frequently in the neighborhood of the spleen, and especially in the gastrosplenic and great 

 omenta, small nodules of splenic tissue may be found, either isolated, or connected to the spleen 

 by thin bands of splenic tissue. Every such nodule is known as a supernumerary or accessory 

 spleen (lien accessorius). Accessory spleens vary in size from that of a pea to that of a plum. 



Support and Mobility of the "Spleen. The spleen is normally movable within certain 

 narrow limits. It moves with respiration and with the stomach movements. It is supported by 

 ligaments (p. 1260). An unduly mobile spleen is called a movable spleen. In order that a 

 spleen shall become unduly movable, the ligaments must stretch, and this stretching is often 

 effected when the organ is greatly enlarged, but even an apparently normal spleen may become 

 movable. Movable spleen is usually associated with movable left kidney. 



Structure. The spleen is invested by a capsule consisting of an external serous and an 

 internal fibromuscular layer. 



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

 and in the human subject is intimately adherent to the fibromuscular layer. It invests the 

 entire organ, except at the places of its reflection on to the stomach and* Diaphragm and at 

 the hilum. 



