THE PERITONEUM 441 



The position of the ventral part depends largely upon two factors — the degree of fulness of 

 the stomach and the size of the spleen. When the stomach is empty or nearly so and the spleen 

 small (contracted), the latter is strongly curved, and its ventral end may be between the left lobe 

 of the liver and the left dorsal part of the great colon. When the stomach is full, it pushes the 

 spleen backward, affecting most the ventral part of the latter. Of course the spleen is affected 

 by the respiratory movements, as may be readily observed by examination per rectum of the 

 living subject. 



The spleen is attached by two peritoneal folds, the suspensory ligament and 

 the gastro-splenic omentum. The suspensory ligament of the spleen (Lig. sus- 

 pensorium lienis) attaches the dorsal end to the left crus of the diaphragm and the 

 left kidney; it contains a quantity of elastic tissue. The dorsal layer of the liga- 

 ment, which passes to the diaphragm, is the ligamentum phrenico-lienale, and blends 

 with the gastro-phrenic ligament; the ventral part, which goes to the kidney, is 

 termed the ligamentum renolienale. The gastro-splenic omentvim (Lig. gastro- 

 lienale) passes from the hilus to the left part of the greater curvature of the stomach. 

 It is narrow dorsally, where it joins the suspensory ligament; ventrally it becomes 

 much wider and is continuous with the great omentum. 



Small globular or lenticular masses of splenic tissue may be found in the gastro-splenic 

 omentum. They are termed accessory spleens (Lienes accessorii). 



Structxire. — The spleen has an almost complete serous coat (Tunica serosa). 

 Subjacent to this and intimately united with it is a capsule of fibrous tissue (Tunica 

 albuginea), which contains many elastic fibers and some unstriped muscular tissue. 

 Numerous trabeculse (Trabeculse lienis) are given off from the deep face of the 

 capsule and ramify in the substance of the organ to form a supporting network. 

 In the interstices of this framework is the spleen pulp (Pulpa lienis), a dark red, soft, 

 grumous material. This is supported by a delicate reticulum, and contains numer- 

 ous leukocjd;es, the large splenic cells, red blood-corpuscles, and pigment. The 

 pulp is richly supplied with blood. The branches of the splenic artery enter at 

 the hilus and pass along the trabeculse. The arteries which enter the pulp have a 

 sheath of lymphoid tissue, which collects on the vessel wall at certain points, form- 

 ing small splenic lymph nodules (Nodull lymphatici henales).^ These are visible 

 to the naked eye as white spots, about as large as the head of a pin. The blood 

 passes into cavernous spaces lined by endothelium which is continuous with the 

 cells of the reticulum of the pulp. From these the veins arise. The splenic vein 

 runs in the hilus in company with the artery and nerves, and joins the posterior 

 gastric vein to form a large radicle of the portal vein. 



Vessels and Nerves. — The arteries are derived from the splenic artery, which 

 is the largest branch of the coeliac artery. The splenic vein lies behind the artery 

 in the hilus; it goes to the portal vein. The lymph vessels go to the splenic lymph 

 glands. The nerves, derived from the cceliac plexus of the sympathetic, accom- 

 pany the vessels. 



THE PERITONEUM 



The general disposition of the peritoneum has been described, and other facts 

 in regard to it were mentioned incidentally in the description of the viscera. It is 

 now desirable to study it as a continuous whole^ (Figs- 351, 352, 353, 377, 378). 



We may consider the peritoneum as consisting of two sacs — a greater and a 

 lesser. The greater sac lines the greater part of the abdominal cavity, and covers 

 most of the viscera which have a peritoneal investment. The lesser sac is an 

 introversion or invagination of the greater sac, formed during the development of 

 the viscera. The two sacs communicate by a relatively narrow passage, termed 



1 These are also known as Malpighian corpuscles. 



2 The student is strongly recommended to study the peritoneum of a foal or other small 

 subject when the opportunity occurs, as in these the viscera are easily handled, and the course 

 of the peritoneum can be followed without difficulty. 



