=The Blood Vascular System.=—A knowledge of the general features of the circulatory system are essential to the undertaker and the embalmer as a means of enabling him not only to perform the ordinary operations and duties of his profession intelligently, but to equip him with the knowledge necessary to meet the exceptional conditions which sometimes arise. There is a growing appreciation of the fact, also, that thoroughness in the practice of embalming is worth striving after. Many cases of embalming, no doubt, require a minimum amount of attention, particularly where the body is to be kept but a short time. Where preservation for longer periods is required, as for transportation, or where disease and accident have interfered seriously with the circulation, a more exact knowledge is evidently desirable. The blood vascular system comprises the heart, which is the central organ of the whole system, and all the blood vessels. This system, with its arteries and veins, permeates the whole body and becomes divided and subdivided at its outer portion into vessels constantly decreasing in size, until those extremely minute vessels, the capillaries, are reached. All the tissues of the body are very rich in these, so that all portions of the body are supplied with blood, which is essential for the nourishment and rebuilding of the tissues. The large vessels which convey blood from the heart are termed arteries, while the vessels which convey the blood back to the heart are termed veins. For one to properly embalm the human body, it is necessary to understand the way the fluid will circulate through the body, and the only way we can do this is to study the circulation of the blood as it would occur in life. To facilitate the description of the blood vascular system, it has been divided into six subdivisions as follows: (1) Systemic. (2) Pulmonary. (3) Coronary. (4) Portal. (5) Foetal. (6) Collateral. =The Systemic Circulation.=—The systemic circulation is called the greater circulation of the body. The course of the blood is from the left ventricle of the heart through the aortic semi-lunar valve to the great aorta and its branches which end in capillaries in the tissues of the body then through the veins the terminal trunks of which end in the right auricle of the heart. So the systemic circulation is the circulation of the blood from the left ventricle of the heart to the right auricle of the heart and this circulation has the important function of carrying oxygen to the tissues to nourish them, and of carrying carbonic acid gas back to the heart which is a waste product of the tissues. The systemic circulation is divided for the sake of convenience into the following: (1) The arterial system. (2) Capillary. (3) The venous system.