THE ^0^-COKTAGIOUS DISEASES. 211 



muscles, joints or other structures. Bheumatism of a 

 joint differs from muscular rheumatism. Every joint 

 is enclosed in a thin membrane in the form of a short, 

 wide tube. The membrane is attached at either end to 

 the margin of the articular surfaces of the bones form- 

 ing the joint. This membrane encloses the various lig- 

 aments, which support the joint. This membrane fur- 

 nishes the secretions or fluids, which lubricate the joint 

 and prevent friction. In acute rheumatism of a joint 

 the irritation causes an increased blood-supply, and 

 there is swelling and redness in proportion to the in- 

 crease in the circulation. The more vascular the part, 

 the greater the swelling. The swelling causes pressure 

 and the pressure causes pain. Eedness or discoloration 

 is caused by the escape of the red blood-corpuscles into 

 the surrounding tissue. With an increase in the blood- 

 supply there is an increase in the tissue changes, hence 

 an increase in the temperature because animal temper- 

 ature depends upon tissue change. 



This gives what are called the four cardinal symp- 

 toms, swelling, redness, heat and pain. Pain is not 

 always present. For instance there may be little or no 

 pain in chronic inflammation of the liver. There may 

 be no pain in inflammation of the solitary glands, called 

 Peyer's glands, in typhoid fever. 



Chronic "rheumatism of joints does not usually follow 

 the acute, but arises insidiously in people who have 

 suffered from exposure, improper food, overwork and 

 other hardships. In chronic rheumatism of joints the 

 cartilage covering the articulating or adjoining ends of 

 bone may become eroded. The exposed bone becomes 



