CHAPTER XI 



GENERAL PATHOLOGIC CHANGES 



THE BLOOD IN DISEASE 



General disturbances of the health are accompanied by 

 changes in either the distribution or the character of the blood, or 

 both. When the various functions of this highly important fluid 

 are recalled, it is readily understood that any alteration in it en- 

 dangers both life and health. 



Normally, both the quantity and quality of the blood are 

 maintained at a point just high enough to meet the requirements 

 of the body. When the demands for blood are great in one set of 

 organs as a result of increased activity, there is a corresponding 

 decreased demand in other parts. An organ rich in blood is said 

 to be congested or hyperemic, while one poor in blood is anemic. 

 In moderation, either condition may be physiologic. Only when 

 these changes have progressed to such an extent that the physio- 

 logic activities are interfered with is a pathologic condition said to 

 exist. 



Congestion, which may be either active or passive, is an in- 

 crease in the quantity of blood in a part. It may be due to an 

 excessive inflow of blood or to a diminished outflow. 



Active congestion is that condition in which the arteries are 

 overfilled with blood. It is caused by agencies which produce an 

 increased flow of blood in the part, such as mechanical and chemical 

 irritants. The part appears slightly larger, redder, and warmer 

 than normal. These changes are due to the fact that the blood is 

 prevented from circulating as it should; for example, congestion of 

 the udder. Long-continued congestion leads to permanent en- 

 largement of the part. Fortunately, it is usually only temporary, 

 so permanent injury rarely results unless complications take place. 

 Active congestion is seen in inflammation, where it is always a 

 symptom. 



Passive congestion is an overfilling of the veins with blood. 

 The affected part becomes larger and bluish red in color. In most 



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