1062 Hypeitroi)l)y ol' tlie Heart. 



velops ill older clogs in consequence of a chronic, especially 

 interstitial, inflammation of the kidneys. 



Heuator sees tlie cause of nephritic liypertrophy, which usually occurs in 

 the left heart, less often in both halves of the heart, in a narrowing of the vessels 

 which is produced by irritating sulistances retained in the blood, and also in an 

 irritation of the heart muscle by these same substances. In certain cases, which 

 may be not a few, the enlargement of the heart probably occurs through the 

 influence of the causes which are responsible for the inflammation in the kidneys. 



The secondary hypertrophy of the heart which occurs in 

 connection with chronic diseases of the heart, lungs, arteries 

 or kidneys is a iDlienomenon of these diseases and will there- 

 fore he considered in connection with them. Here only the 

 so called idiopathic hypertrophy of the heart is to be discussed 

 which arises from an acute cardiac dilatation or is possibly 

 produced by irritating substances that are not known exactly. 



IMany contributions on idiopathic hypertrophy of the heart may be found in 

 veterinary literature; on the basis of their clinical symptoms, however, most of 

 them must be classed rather with chronic myocarditis or with cardiac dilatation. 



Anatomical Changes. The determination of cardiac hyper- 

 trophy requires an exact knowledge of the physiological dimen- 

 sions, the relations between heart and body weight and a con- 

 sideration of the size of the respective heart cavities. 



The relation of the weight of the heart to the weight of the living body 

 in the horse is, according to Franck & Martin, 1% on an average; according to 

 Frey, 1.28%; according to Schubert, 0.84%; in cattle, according to Schmalz, 

 0.3.3-0.42%; according to Schneider, in the steer 0.442%, in the ox 0.414%, in 

 the cow 0.492% ; according to Schubert, in the steer 0.436%, in the ox 0.42%, 

 in the cow 0.52%, and in calves 0.708%; in the dog, according to Schubert, 1% 

 of ilje body weight. 



During moderate contractions the hypertrophy of the 

 muscle may be noticeable even on external inspection, especially 

 if it is only partial. The form of the heart is changed thus 

 that with an increased thickness of the left ventricular wall 

 the heart as a whole is slender, elongated, like a pointed cone, 

 while in hypertrophy of the right ventricular Avail the heart 

 as a whole becomes broader and more flat, the right heart being 

 involved in the formation of the apex; indeed, if the hyper- 

 trophy is very great, the right ventricle reaches beyond the 

 apex of the left ventricle. The thickened muscle is usually 

 firm and like rubber. The weight of the heart is also increased 

 and may in well marked cases amount to twice the normal 

 weight. 



The customary classification of simple hypertrophy (walls thickened, cavity 

 of normal width), concentric hypertrophy (walls thickened, cavity smaller) and 

 eccentric h;si3ertrophy (walls thickened, cavity dilated) is well adapted for a 

 concii^e description of the findings, but it has no particular significance, except 

 that the last form indicates a considerable insufficiency of the previously hyper- 

 trophied heart muscle. 



