It is important to note the fact that the heart is the only structure which contains blood in its substance; in all the other members of the body the blood is contained in the veins. The base of the heart is situated at its highest point and represents the broadest portion of the organ; it is attached to the posterior wall of the chest by a few ligaments, than which no stronger are to be found in any part of the body. These bands do not touch the heart at any point except at the top, where they take their origin; and their great strength is explained by the fact that it is their duty to hold the heart firmly in its proper position. The heart possesses two ventricles or cavities, of which the left one--by reason of the natural position of the organ as a whole--is a little higher than the right. Between these two cavities there is placed a partition which in its turn contains a small cavity--termed by some _the third ventricle_. Above each of the larger ventricles there is a sort of appendix--cartilaginous in structure, but flexible and at the same time strong,--which contains a cavity and has some resemblance to a cat’s ear. These structures, to which the common people have given the name _auricles_, alternately contract and dilate. The purpose for which they exist is to serve as reservoirs for the blood and air that are needed for the nourishment and cooling of the heart. To the right ventricle there comes a many-branched vein which conducts to the heart a coarse, thick and warm blood destined to nourish that organ. The portion of this abundant fluid which is not needed for this purpose is then rendered less coarse and thick by some subtle power possessed by the heart itself, after which it is driven into the cavity that is located within the partition wall which separates the ventricles the one from the other. From this smaller cavity, this so-called third ventricle, in which it receives additional heat and at the same time undergoes further thinning as well as some kind of digestion and purification, the blood passes on into the left ventricle and there undergoes a further change--one which is characterized by the development of that element which we call _spirit_, something clearer, more subtle, more pure, more glorious than any known substance in the human body, and therefore more nearly allied in its nature to celestial things. This new element forms a friendly and very appropriate link between the body and the soul; it is the direct agent or instrument of the latter, conveying to man the different faculties with which he may be endowed.