For the purpose of exhibiting the heart contained within its envelope the pericardium, together with the great vessels connected with it, particularly the aorta, the student is advised, in the first instance, to make a longitudinal incision through the abdominal parietes of about six inches in length, the centre being situated at the umbilicus: the bifurcation of the abdominal aorta should then be exposed, and a full-sized pipe of the injecting apparatus inserted from below upwards into this vessel, about two inches above the origin of the common iliac arteries; the injection should then be directed upwards, towards the heart. By this method the thoracic aorta, the arch of the aorta, its relation to the sternum, together with its other numerous important relations, will be best seen, whilst the arteries of the head, neck, and upper extremities will be much better filled than if the subject were injected from the ordinary situation, the arch of the aorta. The following dissection should now be performed: a perpendicular incision should be made, commencing from below the centre of the clavicle, and passing across the second, third, fourth, fifth, sixth, and seventh ribs of the left side: these bones should then be sawn through, a little in front of their centres, and the cartilage of the first rib of the same side divided. A second perpendicular incision should next be made through the integument covering the sternum, and then through the bone, keeping a little to the right side of the middle line. The lower extremities of these two incisions should now be connected by means of an oblique incision, and the parts included within them should be next raised off carefully from below upwards, and then forcibly turned backwards upon the front of the neck. Whilst making this dissection, the soft parts lying behind the divided portions of the ribs and sternum should be carefully detached from these bones. The mammary artery is particularly liable to injury in this stage of the dissection. By adopting the plan now recommended, the student will be able to expose the pericardium, and to observe its relation to the parietes of the thorax, whilst the relations of the arch of the aorta, the proximity of this vessel to the right side of the sternum, and to the cartilage of the second rib, at its junction with the former bone, will attract his attention. The same plan of dissection may afterwards be pursued at the right side, with this difference, that the cartilage of the first rib should not be disturbed, in order that the dissection of the lower portion of the neck at that side, together with the dissection of the arteria innominata, may bo pursued with advantage.