The _most_ favorable condition, however, for the formation of heart clots, is undoubtedly that in which there is an _absolute_ increase of fibrin, and this we find in a large number of diseases marked by acute inflammatory symptoms; as in pleurisy, pneumonia, diphtheria, croup, acute rheumatism, erysipelas, puerperal fever, etc. In a large number of deaths from these diseases, a post-mortem examination would undoubtedly bring to light a heart clot, which has at least served to hasten, if it has not been the immediate cause of the fatal termination. Again, the formation of heart clots is evidently promoted by any circumstances or conditions, resulting in great feebleness or languor of the circulation, independent of variations in the amount of fibrin. A complete stasis of the blood is certain to be followed by coagulation; as in employment of pressure in the treatment of aneurism; so in cases of great prostration of the powers of life, attended with extreme feebleness of the circulation, as 1st. In cases of shock, where life is not immediately destroyed; 2d. In certain cases of poisoning, as by opium, where the action of the heart is greatly depressed; and 3d. In syncope, either with or without loss of blood. In all of these cases the danger of the formation of the heart clot is very great, and probably in a large number this is the immediate cause of death. It is a fact well established, that loss of blood, either by hæmorrhages or venesection, is followed by an increased coagulability of that fluid; hence, the fearful hæmorrhages which sometimes attend parturition, if accompanied with syncope, are in great danger of being followed by the formation of the heart clot, and thus ending in death.[14] Another circumstance tending to promote the formation of fibrinous clots in the heart, is evidently to be found in the peculiar formation of the valves guarding the auriculo-ventricular openings. It is well known how fibrin may be collected from fresh blood, by beating the same with a bundle of twigs, the latter soon becoming coated with shreds of fibrin; so the _chordæ tendineæ_ and fleshy columns of the heart, between which the blood is continually being driven, affords convenient points for collecting the same from the feebly circulating or overcharged blood; and from the close intermingling of the tendinous cords, with the substance of the clot, it is probably upon these that the deposit first begins to form.