368 APPLIED PHYSIOLOGY 



in old persons, and is due partly to deposits of lime in the cartilage and 

 partly to a dry state of the synovial membrane. 



Sometimes a joint slowly swells and discharges yellow matter for a 

 long time, while the sufferer gradually loses flesh and strength. The 

 disease is commonly known as a white swelling, but is really tuber- 

 culosis, or consumption of the joint. When it affects the hip joint, it 

 is called hip joint disease. A form of the disease without the discharge 

 of matter may affect the spine and produce the deformity called a 

 hunchback. 



SUMMARY 



1. The union of two bones is called a joint. 



2. In joints in which the bones do not move, the bones 



are united either by bone or strong pads of fibrous 

 tissue, or by cartilage, or by being dovetailed into 

 each other. 



3. In flexible joints, bones are joined together by a collar 



of fibrous tissue and by the action of muscles. 



4. Flexible joints are lined with synovial membrane, which 



secretes a fluid like the white of an egg to lubricate 

 the joint. 



5. By assuming one position day after day the joints 



become fixed in that position. 



6. In sprains and dislocations the ligaments are stretched 



or torn, and require long rest in recovery. 



7. The synovial membrane may become inflamed and 



swollen. 



"8. A joint may become affected with tuberculosis, forming 

 a white swelling or hip joint disease. In it the joint 

 forms an abscess and often discharges matter. 



DEMONSTRATIONS 



162. A fowl dressed for the table will illustrate the different kinds of 

 joints. Notice that in some places the muscles unite with the ligament 

 and in others simply cross it, usually as a white cord or tendon. Cut 



