MII Till I IVI k ASH SIM.KKN 157 



h\t on proteids only (with salts and water), and if plenty of 

 proteid is given, the liver will lay down some glycogen. This 

 i^ lu ( .ui^e it is the property of the liver cells to make glycogen, 

 and they can make it if they are supplied with proteids only, 

 but thi-y ran make it much more plentifully from sugar. A 

 small quantity of glycogen is also found in muscle. 



The Spleen 



Structure of the Spleen. The spleen is a dark purplish- 

 red organ about five inches in length, situated, as we have 

 seen, on the left side of the abdomen just below the stomach. 

 It is soft and spongy in texture, that is, is made up like a 

 sponge of a close branching meshwork. The meshwork con- 

 sists of fibrous and elastic tissue, to which is added in man 

 and in most animals a number of plain muscular fibres. A 

 layer of the same tissue on the outside, called the capsule, 

 encloses the organ. In the meshes of the sponge work is a 

 soft pulpy tissue called the spleen -pulp. The spleen -pulp 

 consists of red blood corpuscles and of colourless cells, some 

 of which are branched, while others are small and round like 

 the leucocytes or colourless corpuscles of the blood. Here 

 and there the leucocytes are densely crowded together, form- 

 ing small white nodules. If the spleen of a sheep or ox is cut 

 across these nodules are seen as round white spots in the dark- 

 red pulp. The spleen is well supplied with blood by an artery, 

 the splenic artery, which branches almost directly from the 

 aorta. The smallest branches of the artery open directly into 

 the spleen-pulp. From the spleen-pulp the blood is collected 

 by small veins which gradually unite, forming the splenic veins 

 which carry the blood away to the portal vein and so to the 

 liver. 



Functions of the Spleen. The spleen changes much 

 in size. It becomes largely distended with blood about five 

 or six hours after a full meal, and later on shrinks again. 

 Sometimes it varies in size regularly every two or three minutes, 

 due to the contraction of its plain muscular fibres causing a 

 shrinking, and their subsequent relaxation causing a return 

 to the larger size again. 



