440 



THE CIRCULATORY SYSTEM. 



nective tissue, is of great significance, and it may be the dominant factor 

 in many cases of sudden death. 



Occasionally there is a formation of new connective tissue in the myo- 

 cardium as well as in the endocardium without evident lesion of the coro- 

 nary arteries or the above-mentioned conditions. This growth may be 

 in the form of circumscribed patches, or diffused over a considerable 

 part of the wall of the heart (Figs. 234 and 235) ; in both instances with 

 atrophy of the muscle. Such an interstitial inflammation is often fol- 

 lowed by dilatation of the cavities of the heart, by the formation of aneur- 

 isms of the wall of the heart, and of thrombi in the cavities of the heart. 



FIG. 236. CHRONIC INTERSTITIAL MYOCARDITIS. 

 Showing cross section of a papillary muscle 



The muscle tissue is least involved about the vessels and near 

 the surface. 



It is believed by many observers that the new connective tissue which 

 develops in the heart in connection with atrophy of the muscle fibres, as 

 a result of impaired nutrition due to a narrowing of the lumen of the 

 coronary arteries, is not in the stricter sense inflammatory in its nature, 

 but is rather a, fibrous hyperplasia, the new-formed connective tissue form- 

 ing secondarily, to replace the muscle fibres which have atrophied. It is 

 interesting in this connection to note that under these conditions the mus- 

 cle fibres immediately beneath the endocardium and close around the 

 blood-vessels where the nutritive supply is most abundant are often not 

 atrophied, nor is the growth of connective tissue marked (Fig. 236). 



Tuberculous Myocarditis is of occasional occurrence and may be asso- 

 ciated with tuberculosis of the pericardium or endocardium. ' 



"Consult Moser, "Tuberculosis of the Heart." Reports of the Boston City Hospital, 

 eleventh series, p. 194, 1900. Also Anders, Jour. Am. Med. Assn., November 1st, 1902 



