152 ANATOMY AND PHYSIOLOGY 



spleen. The peritoneal covering completely surrounds it, except 

 to allow vessels and nerves to pass through the hilus. 



The function of the spleen is not well understood, as both 

 animals and human beings have been known to live in health after 

 its removal, but its structure and the study of the blood of the 

 splenic artery and splenic vein reveal the following facts: 



The spleen pulp contains a vast number of white cells (chiefly 

 lymphocytes) and many disintegrating red cells. It has a high 

 percentage of iron, especially after chronic diseases. The blood in 

 the vein which leaves it contains many more white cells than that 

 in the artery which enters; also many small red cells are present, 

 some of which are still nucleated (newly formed). Two enzymes 

 are found one a uric-acid-forming enzyme. 



From these observations the conclusions suggested are that the 

 spleen gives birth to leucocytes; that it stores and works over the 

 iron from broken-down tissues (including red cells); that it may 

 assist to form red cells and that it forms uric acid from broken- 

 down protein substances. 



Clinical notes. The elasticity of the capsule allows frequent variations 

 in size, which in health are normal; it is always larger during digestion and 

 smaller in fasting. In certain diseased conditions it is much increased in 

 size, as in malaria; and notably in leukemia, which is characterized by an 

 enormous increase in the number of white cells in the blood, as well as in the 

 size of the organ itself. The significance of these variations in size is not yet 

 explained. 



