The injection should be performed in a slow, regular manner. After a quart of the embalming fluid (the composition of which has been given above) has been injected, the operation should be suspended for about ten minutes, after which it should be renewed in the same manner, until a gallon and a half or two gallons have been injected. Sometimes the quantity injected need not be so great, as for instance in the case of a person much emaciated by long illness, or if the subject be a child. The jugular veins must be kept open so long as the flow of blood continues, but they must be closed as soon as the embalming fluid makes its appearance. The best manner of closing the veins is by introducing into the jugulars a small pad of cotton, and neatly sewing up the opening. It should be remembered that the cloth moistened with the solution for the face should be kept on, well saturated, while this operation is being performed, and even for a few hours after the body has been dressed. A body prepared in this manner has been kept, in a wooden coffin, in a dark and moderately cool place, for the space of nine months without any perceptible change. After that time the shrinking of the tissues took place, and the body was slowly drying up and being desiccated without in the least decaying or putrefying. THE ARTERIAL SYSTEM. To understand thoroughly the process of embalming as described in the preceding chapter, it will be necessary to give here a brief explanation of the circulatory system; also to explain the position of the different parts of the viscera, to which reference has been made. The arteries commence from the great arterial trunk, called the aorta, and their branches are distributed to all parts of the system; they are dense in structure, and preserve for the most part their cylindrical form when emptied of their blood, which is their condition after death. The aorta arises from the left ventricle, at the middle of the root of the heart; it ascends at first forwards and to the right, then curves backwards and to the left, and descends on the left side of the vertebral column, to the fourth lumbar vertebra; here it is divided into the arch and descending aorta. It should be here remembered that most of the branches, which spring from the great artery and vein, are double, that is, each right branch has a corresponding one on the left side—so that there are, for instance, the right and left carotid arteries, the right and left jugular veins, etc. From the arch of the aorta are sent off those arteries which are distributed to the head and arms; the principal ones among these are named as follows: