H.H. may be used later, if there is any dimness of the eye left. Sometimes pieces of hay or chaff get into the eye and cause a great deal of irritation; of course the first thing to be done is to carefully remove them, and then apply the MARVEL, diluted with half water, which, in the majority of cases, is all that is necessary to be done. CHAPTER V.—PART I. DISEASES OF THE CIRCULATORY SYSTEM Structure and Action of the Heart Before entering on a description of the diseases of the Heart, it may be well to give a brief description of that organ and its functions, for the benefit of non-professional readers. The heart is placed in the center of the thorax, in the space between the lungs, and opposite the third, fourth, fifth and sixth ribs. It may be described as a muscular forcing pump, for the transmission of blood to all parts of the body. The texture of the heart is muscular, with tendinous or cartilaginous bands around the openings between the auricles and ventricles, and between the latter and the arteries. It contains four chambers, viz.: two auricles and two ventricles; each auricle communicates with its corresponding ventricle; but the auricles do not communicate with each other, nor do the ventricles. The opening in each pair is guarded by a little valve, in order to ensure the flow of blood in one direction, and to prevent any regurgitation or re-flow from the ventricles into the auricles. We find valves for a similar purpose placed at the origin of the pulmonary artery and the aorta, which proceed from the right and left ventricles, and are the channels by which the blood flows through the former to the lungs, through the latter to the general circulation. The chambers of the heart are lined by a smooth membrane of a serous character, called the endocardium, which is often the seat of disease; and the whole is enclosed in a fibro-serous sac, called the pericardium. On examining the heart, it will be found externally divided by a furrow, which corresponds with a muscular septum, dividing the organ into two parts, or two hearts, having no direct communication with one another, except in the fetus. The right side, whose parts are thinner than the left, may be called the venous heart, as it receives the blood in an impure state from the veins, and transmits it through the pulmonary arteries to the lungs, where it becomes exposed to the atmosphere, and converted from venous into arterial blood. It is then conveyed by the pulmonary arteries to the left auricle and ventricle, whence it is propelled through the aorta and its branches to all parts of the body.