CHAPTER XI 

 GENERAL PATHOLOGIC CHANGES 



DISEASES OF THE BLOOD 



General disturbances of the health are accompanied by changes 

 in either the distribution or the composition of the blood, or both. 

 When the various functions of this highly important fluid are 

 recalled, it is readily understood why 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 correspond- 

 ing increase in action on the part of the heart to supply the 

 demands. 



Various diseased conditions of the blood are recognized. 

 Many of the terms used for them end in "emia," which signifies 

 blood. For example, there are hyperemia, anemia, hydremia, 

 septicemia, pyemia, and sapremia, each of which will now be 

 briefly discussed. 



Hyperemia or congestion is applied to an increase in the quantity 

 of blood in a part. When it is not marked it is normal; for 

 example, a flush of the face from embarrassment. When pro- 

 nounced and long continued it is a sign of disease. It may be 

 either active or passive. 



Active hyperemia is the 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 enlargement of the part. Fortunately, it is usually 

 temporary, so permanent injury rarely results unless complica- 

 tions take place. Active congestion is seen in inflammation of 

 which it is always a symptom. 



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