CHAPTER V. 

 CIRCULATORY DISTURBANCES. 



Xormal blood circulation is dependent npon the rate, rhythm 

 and force of the heart, the caliber <<{ the blood vessels and the 

 resistance ottered by them and the quantity and the quality of 

 the blood. 



Variation of Heart Action. — A marked \'ariation in the heart 

 activity results in imperfect circulation. Depressed tor dimin- 

 ished heart actici is more common than increased heart action. 

 Diminished functional activity is most fre(|uently caused by in- 

 flammation of the endocardium, myocardium, epicardium or per- 

 icardium. \'alvular stenosis and valvular insufihciency are the 

 result of endocarditis. ^lyocarditis diminishes the activity of 

 the heart and if the inflammation is lonq- continued the muscle 

 cells are destroyed and replaced bv fibrous tissue thus per- 

 manently impairing the force of the heart. Inflammation of the 

 epicardium and pericardium mav be accompanied by volumin- 

 ous exudation which distends the pericardial sac and produces 

 sufficient pressure to liinder diastole, or the exudate mav be- 

 come coagulated and later organized attaching the sac to the 

 surface of the heart and thus hindering cardiac systole. Cardiac 

 activity mav be diminished b\- the collection of fluid in the 

 ])leural cavity, malformed thoracic cavity, tumors, occlusion of 

 Coronary arteries, fatigue and thrombic formation upon the 

 cardiac valves. Diminished cardiac actiyit\' results in a dimin- 

 ished quantit\- of blood being sent out from the heart and an 

 accumulation of waste [iroflucts in the tissues. 



Inereased functional actii'ity of the heart is usually only tem- 

 porary excepting in those animals afifected with cardiac com- 

 pensatory hypertrophy The most common cause of increased 

 cardiac acti^ itv is reflex stimulation. Increased activity due 

 to reflex stimulation \m\ terminate in exhaustion and svncope 

 in a relatively shr.rt time. Increased functional activitv. due 

 to a cardiac compensatory hypertrojjhy resulting from increased 

 resistance as in emphysema, chronic nephritis, etc., may result 

 in permanent over action of the heart. 



Anatomical changes in the cardiac-structure, as hypertrophy, 

 fatty degeneration, fragmentatirm, fibrous formation, or necrosis 



11(1 



