SUPPORTING TISSUES 77 



abdominal cavity, and are attached to each other and to the 

 walls of the cavity by means of the peritoneum. A portion of 

 the peritoneum, called the mesentery, holds the intestines to the 

 backbone. If any organ of the abdomen is removed a part of 

 the peritoneum must be cut to separate that organ from other 

 organs. 



The outside of the body may be compared with a body cavity 

 in that it is covered with epithelial tissue called skin. The outer 

 layers of the tissue become flat and horny, and the outermost 

 ones are dead. The hair and nails develop from certain skin 

 cells. 



Supporting tissues. These tissues are all alike in that they con- 

 nect and support the other tissues of the body. They, in con- 

 trast with the epithelial tissues, are noted for the abundance of 

 intercellular material. The main supporting tissues are bone, 

 cartilage, white fibrous, yellow elastic, and fat or adipose tissue. 



Problem. Study of cross structure of bone. 

 Obtain some rib bones of a lamb from the butcher. 



I. Let some of the rib bones stand in a ten-per cent solution of hydrochloric 

 acid for at least two weeks. 



A.' How does this treated bone differ from ordinary bone in appearance 

 and texture? The acid dissolves out the intercellular deposits of mineral 

 matter, leaving only the organic material. 



B. State the importance of mineral matter in the bone. 



II. Burn some rib bones in a very hot flame. 



A. How does the burned bone differ from ordinary bone? Since or- 

 ganic material burns, the bone cells were destroyed, leaving only the 

 intercellular mineral matter. Bone consists of a combination of bone 

 cells and intercellular material. This intercellular material is deposited 

 by the bone cells. It is mineral matter, largely calcium phosphate and 

 carbonate. 



B. State the importance of the cells in the bone. 



Secure some shank bones or other long bones from the butcher. Have him 

 saw one lengthwise so that the interior of the long bone, including the enlarged 

 head, may be studied. 



