380 DISEASES OF THE HEART. 



The coagula which form prior to death are mainly the result of the 

 feeble manner in which the heart contracts. Hence, they a^e com- 

 monly found among marasmic subjects, and in persons who have de- 

 generation of the heart. Then* points of origin are always the shallow 

 recesses between the trabeculae, which readily dilate when the heart is 

 relaxed or softened, so that, if its contractions be incomplete, the blood 

 in them stagnates and coagulates. In very rare instances an embolus 

 may, perhaps, form the nucleus of a clot. 



When coagula form in the heart during the death-throes, they may, 

 no doubt, occasion some obstruction to the circulation, but it is impos- 

 sible to know how much of the feebleness of the circulation is due to 

 the palsy of the heart, and how much to obstruction of the orifices by 

 clots. Even if the clots produce murmurs, they cannot be distin- 

 guished from the murmurs caused by irregular and imperfect action 

 of the heart. This is true also for the clots which form prior to the 

 death-agony, as they, too, form in case of feeble cardiac action and 

 impeded circulation. 



CHAPTER XIII. 



CONGENITAL ANOMALIES OF THE HEAET. 



ETIOLOGY. The majority of congenital defects of the heart are 

 due either to arrest of development (the organ remaining in a condi- 

 tion which was normal during foetal life), or else to foetal endocarditis 

 or myocarditis. We are unacquainted with the causes of this arrest 

 of development, as well as with the causes of the foetal inflammation. 



Prominently in the former class of congenital deformities of the 

 heart stands incompleteness of the septa ; in the second class, the in- 

 durated strictures produced by inflammation, and congenital stricture 

 and insufficience of the valves, are the most important. The latter 

 occur generally in the right heart, which, after birth, is very rarely 

 attacked by endocarditis or myocarditis. 



The causes of congenital malformation in position of the heart may 

 be similarly classified. Sometimes they are to be regarded as cases of 

 arrested development, the ribs, the sternum, and the clavicles being 

 imperfectly formed, so that a greater or smaller portion of the heart is 

 covered by soft parts alone. In other cases they depend upon inflam- 

 mation during foetal life, which has given rise to adhesions with neigh- 

 boring organs. 



The pathogeny of dextro-cardia, in which the heart lies on tho 

 right side of the thorax, the liver generally occupying the left hypo- 

 cliondrium, and the spleen the right, etc., is altogether obscure. 



