208 CIEC0LATION 



two processes of repair are called inflammatory processes, 

 and inflammation is usually defined as " the local attempt 

 at repair of an injurj^." 



Examples of simple inflammatory processes. — ^When the mucous 

 membrane is injured by exposure to cold, there results a conges- 

 tion in the membrane. This congestion may be complicated by 

 the presence of bacteria. In such congestion the formation of 

 pus is accompanied by an increased activity and secretion of the 

 mucous cells. The combined secretion and pus collects in the 

 passages inclosed by these membranes and forms the discharge 

 common to colds. This congestion of the mucous membrane 

 may be brought about bj' the action of the cold upon the vaso- 

 motor nerves which control the artery supply to the skin. In this 

 event their action is to cut off the blood supply to the skin, and 

 the excess of blood thus cut off is forced to accumulate in the 

 mucous membranes and produce congestion. If this congestion 

 and inflammatory process is confined to the nasal passages the 

 result is called a cold in the head, or catarrh. If in the throat, 

 it may result in swelled tonsils and a sore throat. If in the bron- 

 chia passages, it is called bronchitis, while in the lungs it may 

 produce pneumonia. "When certain bacteria attack the throat 

 membranes the result may be severe. Such an instance is seen in 

 diphtheria. 



Another example of inflammatory processes is found in the 

 pimples and boils. In these cases, bacteria are introduced in some 

 way into the underlying layers of the skin where they cause the 

 death of the surrounding cells. Congestion results, and the leuco- 

 cytes dissolve the dead cells and devour the bacteria forming a 

 greater or less quantity of pus. The pus thus formed softens the 

 surface layers of skin and forms a head or weali spot on the 

 surface through which the pus may ultimately be discharged. 

 "Taking cold in a boil" is actually a case of accidental intro- 

 duction of bacteria into a partly discharged boil, and the resultant 

 formation of new pus, and has no connection whatever with 

 cold. 



The introduction, by the blood, of bacteria into the internal 



