368 THE HUMAN BODY AND ITS FOOD 



such drugs are often very injurious. No medicine of 

 this sort should be taken or given unless a competent 

 physician prescribes it. 



372. Summary. Physiology is the science that has to do with the 

 organs of animals and plants, and with the functions of the organs. 



Man is a vertebrate. His body has a dorsal and a ventral cavity. 

 The dorsal cavity contains the brain and spinal cord. The ventral 

 cavity consists of the thorax and abdomen. These are divided by the 

 diaphragm. 



The body is composed of living cells. A group of cells, all of which 

 do the same kind of work, is called a tissue. 



Bones are made chiefly of connective tissue stiffened with limestone 

 and calcium phosphate. Cartilage is pliable, immature bone. 



Joints are places where bones come together; they are movable or 

 immovable. 



At movable joints bones are held together by ligaments. Movable 

 joints may be hinge, ball and socket, or gliding joints. 



The skeleton consists of 206 bones. 



Muscles are structures that move the body. Their duty is to grow 

 shorter. Muscles are made of muscle tissue and connective tissue. 



Tendons are the extensions of the muscles' connective tissue. 



The bones act as levers, muscles being the "power." 



Muscles are voluntary or involuntary. 



When bones of a joint are separated, the joint is said to be " dis- 

 located." In a t ' sprain " the bones remain together, but the ligaments 

 are injured. 



We eat food (1) to provide for cell growth and repair; (2) to provide 

 energy for the cells. 



There are 5 simple foods, or nutrients: proteids, carbohydrates, 

 fats, minerals, and water. Proteids give material for the growth and 

 repair of cells, also a little energy. Carbohydrates and fats give 

 energy. 



The tube in which digestion occurs is the alimentary canal, or diges- 

 tive tract. Digestion is carried out by liquids taken from the blood 

 (secreted) by organs called glands. 



