LECTURE XIV. 

 PATHOLOGY. 



Physiology is the study of the body organs and their func- 

 tions in health. 



Pathology is the study of diseased organs and their disor- 

 dered functions. Healthy conditions are taken as a basis for 

 studying the diseased conditions. Pathological processes are but 

 healthy ones modified. 



HYPERAEMIA— CONGESTION. 



There are two kinds of hyperaemia, active and passive. 



In active hyperaemia there is excess of blood in the arteries 

 of some tissue or organ. This condition may be due to excessive 

 strength and activity of the heart and want of strength and 

 elasticity in the arteries of that part, allowing them to stretch. 



Passive (venous or mechanical) hyperaemia is a condition 

 in which the current of blood is slowed and there is excess of 

 blood in veins and capillaries. The condition may be due to 

 weakened heart action or to obstruction in arteries or capil- 

 laries. The local changes that may follow passive congestion 

 are exudation of plasma with some red and white corpuscles, 

 and later gangrene. An active hyperaemia, on the other hand, 

 may lead if long continued to enlargement of the part or organ. 

 The vessels themselves may enlarge to several times their former 

 size. 



INFLAMMATION. 



Definition. —A pathological process, marked by pain, heat, 

 redness and swelling. These are called the cardinal SN'mptoms. 



The changes which occur during inflammation are: (i) dila- 

 tation of arteries and veins; (2) current velocity increased at 

 first, then decreased; (3) when current begins to decrease the 

 corpuscles collect in capillaries and small veins and adhere to 



