VALVULAR DEFECTS. 143 



is imperfect heart-action; every defect of an arterial opening in- 

 terferes with perfect ventricular action and every defect in a venous 

 opening causes a corresponding lessening of power in the auricle. 



Fig. 40. 



' Diagram of the blood-circulation. 



An abnormal pumping of the blood in this manner is sure to 

 cause more or less disturbance of the entire organism, but there 

 are certain compensatory processes in the heart itself that tend to 

 overcome this. As a consequence of the impaired flow the heart- 

 muscle is worked much harder and becomes hypertrophied (com- 

 pensating heart hypertrophy). We often see cases where defects 

 of the aorta become equalized by a hypertrophy of the left ven- 

 tricle. In valvular defects of the mitrals the stagnation of the 

 blood occurs in the veins, capillaries, and arteries of the lungs, 

 and as far back as the right ventricle, which becomes dilated and 

 hypertrophied while trying to take up the extra vrork thrown on 

 it. In course of time we also see hypertrophy and dilatation of 

 the left ventricle, and during diastole the stagnated blood runs in 

 great quantities into it out of the dilated auricle. 



These compensating processes of the heart are apt to prevent 

 for a long time any great functional disturbance, provided the 

 heart receives its proportional nutrition. If this is not the case, 

 for instance, in anaemic and cachectic, feverish animals, the com- 

 pensating heart hypertrophy is not present or is only developed to 

 a slight degree, and also in cases of insufficient nutrition, due to 

 some alteration in the coronary artery, the heart is no longer able 

 to satisfy the demands claimed from it and tires out, and all the 

 effects of blood- stagnation rapidly show themselves. 



