19. For since, according to the account we have given, the heart which kindles by its warm breath the individual parts, is the most important of the vital organs, our Maker caused it to be operative with its efficacious power at all points, that no part of it might be left ineffectual or unprofitable for the regulation of the whole organism. Behind, therefore, it enters the lungs, and, by its continuous motion, drawing that organ to itself, it expands the passages to inhale the air, and compressing them again it brings about the exspiration of the imprisoned air; while in front, attached to the space at the upper extremity of the stomach, it warms it and makes it respond by motion to its own activity, rousing it, not to inhale air, but to receive its appropriate food: for the entrances for breath and food are near one another, extending lengthwise one alongside the other, and are terminated in their upper extremity by the same boundary, so that their mouths are contiguous and the passages come to an end together in one mouth, from which the entrance of food is effected through the one, and that of the breath through the other.