1310 THE SKIN, MAMMAR/ GLANDS AND DUCTLESS GLANDS 



diaphragm and the stomach and separates the diaphragmatic from the gastric 

 surface (figs. 1062-1065). 



The posterior border [margo posterior] is rounded, shorter, and straighter than 

 the anterior border and is notched in less than a third of the cases. It separates 

 the diaphragmatic from the renal surface and is lodged in the angle between the 

 left kidney and the diaphragm (figs. 1062-1065). 



The intermediate border is a blunt ridge dorsal to the hilus, separating the 

 gastric from the renal surface. 



It may be clearly defined or more or less obscure and often shows a marked tubercle (fig. 

 1064). When the stomach is contracted and the colon distended this border divides caudally 

 into ventral and dorsal limbs both of which may be well marked or either may be deficient 

 depending on the direction and degree of pressure of surrounding organs. When well marked 

 there is produced at the point where the two limbs diverge a more or less marked projection, the 

 intermediate extremity or angle (fig. 1063). 



The superior extremity [extremitas superior], usually larger than the inferior 

 extremity in the wedge-shaped spleens but smaller in the tetrahedral form, is 

 rounded and bent medially. It extends as high as the tenth thoracic vertebra and 

 lies 1 to 2 cm. from the vertebral column. 



The inferior extremity [extremitas inferior], also somewhat rounded, is directed 

 toward the left and caudally. It is in relation with the phrenicocolic ligament. 



When the stomach is contracted and the colon distended the inferior extremity becomes much 

 broader, in extreme cases forming a distinct inferior border ending ventrally in the anterior 

 margin as an anterior extremity and dorsally in the posterior margin as the posterior extremity 

 (fig. 1063). 



In the tetrahedral-shaped spleen the additional surface produced by the pres- 

 sure of the colon is known as the basal or colic surface (fig. 1063). This varies in 

 size reciprocally with the degree of pressure of colon and stomach. 



When well developed the cohc surface is concave and is separated from the renal and gastric 

 surfaces by the more or less sharply defined dorsal and ventral limbs of the intermediate border 

 and separated from the diaphragmatic surface by an inferior margin produced from the broadened 

 inferior extremity. The left flexure of the colon is in contact with the greater part of this sur- 

 face, but the pancreas also usually lies against it in its cephalic part (fig. 1063). 



Peritoneal relations. — The surface of the spleen is completely covered, except 

 for a small area at the hilus, by a peritoneal coat, the tunica serosa. Ventral to 

 the hilus a double layer of peritoneum is prolonged from the spleen to the left 

 side of the greater curvature of the stomach and the left edge of the ventral layer 

 of the great omentum, forming the gastrolienal ligament which contains the short 

 gastric arteries and veins. Dorsally a second double layer of peritoneum extends 

 from the hilus to the ventral surface of the kidney and the caudal surface of the 

 diaphragm forming the phrenicolienal (lienorenal) ligament. This ligament 

 encloses the splenic artery and veins as they pass to and from the spleen. It is 

 also between the two layers of peritoneum of this ligament that the tail of the pan- 

 creas reaches the spleen (fig. 1065). Except by these two ligaments the spleen 

 has normally no attachment to the abdominal wall or to any of the surrounding 

 viscera. The gastrolienal, and more especially the phrenicolienal ligament, serve 

 in a measure to anchor the spleen in its place in the abdominal cavity but in addi- 

 tion to these the spleen is supported by a fold of peritoneum which extends from 

 the left colic flexure to the parietal peritoneum over the diaphragm, the phrenico- 

 colic ligament. This serves as a sling in whicli the inferior extremity of the spleen 

 rests. The spleen, however, is held in position in the abdominal cavity mainly by 

 the intraabdominal pressure. 



Topography. — The superior extremity of an average-sized spleen is located between the angle 

 and tuborflc (jf the tenth rib on tlie left side and about 3 to 4 cm. from the median line on a level 

 with tlie sjjinous process of the ninth thoracic vertebra. In the majority of cases, it does not 

 extenfl more tlian 2 cm. either cephalic or caudal to a transverse plane at the level of the infra- 

 sternal notcli. The inferior extremity reaches nearly to the midaxillary line in the tenth inter- 

 costal space and 10 to 1.5 cm. from the superior extremity. The long axis therefore corresponds 

 nearly to the shaft of the tenth rib. Tlie posterior border lies beneath the cephalic border of 

 the eleventh rib. The whole spleen (unless enlarged) lies dorsal to a plane passed through the 

 midaxillary lines and is lateral to a line from the left sternoclavicular joint to the tip of the 

 left eleventh rib. In deep inspiration the spleen is greatly depressed and if enlarged may be 

 felt beneath the ribs. 



Variations. — From the mean weight between 150 and 200 gm. there are wide variations. It 

 is not rare to find spleens weighing 80 to 100 gm. and they are recorded as light as 10 and 



