THE SPLEEN. 303 



The arteries, on entering the spleen, at once break up into 

 branches which pass in all directions, giving off twigs on all sides 

 and at varying angles; from these capillaries are supplied, which 

 traverse the parenchyma in all directions. The capillaries empty 

 themselves partly into veins, partly into the splenic spaces. 



The veins commence either as capillaries in connection with the 

 arteries or by communicating with the splenic spaces. This com- 

 munication is brought about by small twigs of about 0-015 mm. 

 diameter, which have incomplete walls, and so open into the splenic 

 spaces (Hoffmann). 



Malpighian bodies are represented by collections of splenic 

 cells on various arterial twigs ; they are, however, not so sharply 

 defined as is the case in some higher animals.] 



IV. THE PERITONEUM. 



a General description. The peritoneum is a thin, pigmented 

 membrane lining the abdominal cavity. Tracing it forwards from 

 the ventral wall of the abdomen (Peritoneum parietale), it can be fol- 

 lowed along the deeper surface of the muscles to the pericardium. 

 The middle portion leaves the abdominal wall by accompanying the 

 anterior abdominal vein ; the lateral portions are continued further 

 forwards, and then ascend on the pericardium and the deeper sur- 

 faces of the lateral walls in the thoracic region. 



The peritoneum passes thence to the ventral surface of the liver 

 (Ligament um corona riina}, covers this surface and passes on to the 

 dorsal surface of the organ, which, together with the gall-bladder, it 

 completely encloses. The membrane thus reaches the dorsal wall 

 (Ligamentv.ni suspensoriv.m liepati* et pericardi'i); from the lateral 

 borders- of the liver it passes upwards to the dorsal wall, and thus 

 forms a pocket-like pleuro-peritoneal cavity on either side. 



From the dorsal wall and above the attachment of the coronary- 

 ligament of the bladder the peritoneum reaches the root of the 

 lung on each side, and completely invests the organ : while in 

 the middle line it covers the outer surface of the oesophagus and 

 attaches it to the dorsal wall, thus forming the first part of the 

 mesentery 



