THE CIRCULATORY SYSTEM. 437 



blocking of one main trunk of the coronary artery may cause sudden 

 death this is not always the case. The interventricular branch of the 

 left coronary artery is the most frequent seat of thrombosis, so that in- 

 farction which usually follows thrombosis is most often situated in the 

 anterior wall of the left ventricle and the lower portion of the interven- 

 tricular septum. The characters of such infarctions and the processes 

 which follow are given below. 



Embolism of the coronary arteries is much less common than thrombo- 

 sis and may be followed by similar lesions of the myocardium. Infec- 

 tive emboli are frequent excitants of suppurative lesions of the myocar- 

 dium. 



INFLAMMATION. 



MYOCARDITIS. 



The inflammatory changes in the walls of the heart involve primarily 

 the interstitial tissue and blood-vessels, the muscle fibres being secon- 

 darily affected by atrophic and degenerative changes. 



Interstitial Myocarditis may be acute and suppurative, or chronic with 

 the formation of new connective tissue. 



Acute Suppurative Myocarditis may be diffuse, infiltrating the wall of 

 the heart with pus. This may occur as a complication of infectious dis- 



C? - ". ' _-- I ~~~ - '" "i**^^ 



FIG. 233. BACTERIAL EMBOLUS IN HEART MUSCLE. 



The bacteria have multiplied since lodgment in the small vessel, so that the latter is widely distended. The 

 surrounding muscle is necrotic. 



eases, such as scarlatina, diphtheria, typhoid fever, gonorrhoea, : or may 

 be associated with ulcerative endocarditis. 3 



More frequently the suppurative inflammation is circumscribed, re- 

 sulting in abscesses. These occur with pyremia, mycotic ulcerative endo- 

 carditis, and other infectious diseases. They are of different sizes and 

 either single or multiple. They are produced by the lodgment of infec- 



1 For a consideration of gonorrhceal myocarditis, consult Councilman, American 

 Journal of the Medical Sciences, vol. cvi., p. 277, 1893. 



- For a special study of this mode of origin see Josserand and Bonnet, Arch, de 

 Medecine exp. et d. Path, anat., t. xi., p. 570, 1899. 



