In the case of injecting an entire animal, such as a rabbit, rat, or guinea pig, the injection is best made a few minutes after death. The animal may be chloroformed, and then bled to death by opening a large vein. As soon as death has occurred incise the skin over the thorax in the middle line. Cut through the costal cartilages to the right of the sternum, and through the junction of the manubrium and body of the sternum. These incisions being for most part through non-vascular parts will not lead to escape of fluid during injection. The sternum being forcibly raised towards the left, the pericardium will be exposed and must be carefully divided. An incision must be made into the left ventricle, and a cannula passed up into the aorta and firmly secured by a ligature passed round the aorta with the assistance of forceps or an aneurism needle. Any blood is cleaned away and the animal is then placed in the water bath for about ten minutes. The tube from the bottle containing the injection fluid is then filled by gentle pressure on the syringe, and clamped when full. Its end is then placed on the cannula and secured there by a ligature. The pressure should be raised by squeezing the syringe until the manometer registers one inch. The clamp should then be removed and the injection commenced. The pressure should be raised very gently and constantly by working the syringe, and the condition of the gums, lips, and eyes of the animal observed. The gums will soon shew a pink tinge. The best indications are obtained by watching the effect on the small vessels of the sclerotic. When these are completely filled, which will be in about five to ten minutes according to the rate at which the air pressure has been increased, the injection may be stopped. This result will be obtained, under good conditions, before the manometer indicates a pressure of five inches. The aorta should now be ligatured, and the animal placed in cold water frequently renewed until it is thoroughly cooled. The organs may then be removed and placed in methylated spirit and hardened. Sections are afterwards cut and mounted in the usual way. CHAPTER IX. DIRECTIONS FOR PREPARING INDIVIDUAL TISSUES.