Compensatory Hypertrophy. 255 



comparison with the sheep. There are marked differences in this con- 

 nection between those birds which are good fliers and the domes- 

 tic fowls which stay more on the ground. (For details cf. Kitt, 

 Pathol. Anatomic dor Haustierc, 11 Bd. Chapter on the Heart. 

 \ei-l. V. F. Enke, Stuttgart. II Aufl. 1901.) 



All diseases which increase the work of emptying the ventricles 

 of the heart in the period of systole and which force the heart to 

 continuously increased pumping effort, give rise to cardiac hyper- 

 trophies, usually confined to one part of the organ according to the 

 position of the opposition to the cardiac effort. Chronic valvular 

 lesions, which interfere with the ready passage of the blood from the 

 auricles into the ventricles, after a primary dilatation of the 

 auricles cause hypertrophy of the auricular walls; stenosis of the 

 semilunar aortic valves causes hypertrophy of the left ventricle, 

 stenosis of the pulmonar}- valve a hypertrophy of the right ventricle ; 

 It is only by a heightened muscular force that the blood can be 

 pressed forward in such conditions. If the cardiac hypertrophy 

 is for a long time sufficient to accomplish the increased demands 

 put upon its functional capability and thus prevents the serious 

 results of tlie original disease or compensates for them, it is spoken 

 of as a compensatory hypcrtropJiy. 



Smooth muscles also become hypertrophied in case of increase 

 of function, physiologically seen in the pregnant uterus, patholog- 

 ically observed in marked degree in the intestinal wall where con- 

 strictions in the lumen gradually develop, over which the chyme can 

 be driven only by increased peristaltic force. The same thing is 

 seen in case of the urinary bladder, resulting from narrowing of 

 the neck of the viscus by prostatic enlargements or from involve- 

 ment by urinary calculi, etc. : and in the oesophagus in case of stric- 

 tures. In all these cases there occurs both a multiplication and an 

 increase in size of the muscle cells. 



In the glands of the body true hypertrophy and the necessity for 

 increased effort become apparent where smaller or larger portions 

 of the glandular parenchyma are destroyed, and are restored or re- 

 placed by regeneration. In case this cannot fully obtain or does 

 not occur at all, as in the liver tissue (after echinococcosis or chron- 

 ic inflammations) the remaining portions of the organ become en- 

 larged and the general volume of the liver may thus become greater 

 than normal. Especially in case of bilateral organs where one be- 

 comes entirely incapable of function, the remaining one acts for 

 the former, performs a correspondingly greater amount of work 

 and hypertrophies (compensatory or vicarious hypertrophy). Where 



