The inferior vena cava is formed by the union of the two common iliac veins; it ascends along the front of the vertebral column or back bone, and, passing through the fissure in the posterior border of the liver, terminates into the inferior part of the right auricle of the heart. Its branches are the lumbar veins, three or four in number, which collect the blood from the muscles and integuments of the loins and spinal veins; the renal veins, which return the blood from the kidneys, and the hepatic veins in the liver. The common iliac veins, which, by their union form the inferior vena cava, are in turn formed by the union of the internal and external iliac veins; the external iliac vein passing into the thigh becomes the femoral vein, and is found in the same sheath with the femoral artery; further below it becomes the popliteal vein; about one inch and a half below Poupart’s ligament in the upper part of the thigh, the femoral vein receives the internal saphenous vein, which commences at the inner side of the foot and great toe; it ascends in front of the inner ankle and along the inner side of the leg; it then passes behind, and along the inner side of the thigh to the saphenous opening, where it pierces the sheath of the femoral vessels and terminates as above stated, in the femoral vein. The above explanation of the circulatory blood vessels is given only for one side of the body—the right side. The other vessels branching off from the two great trunks, the aorta and the vena cava, on the left side are the same, with very slight modifications. DIGESTIVE ORGANS. The œsophagus is a slightly flexuous canal, inclining to the left in the neck, to the right in the upper part of the thorax; it commences at the termination of the pharynx, which is a musculo-membranous sac, about four inches in length, and communicating with the cavity of the nose and mouth; the œsophagus then passes behind the arch of the aorta to the œsophagal opening in the diaphragm, where it enters the abdomen, and terminates into the stomach. The stomach in man is an oblong, membranous bag, placed obliquely across the abdomen and just below the diaphragm; its average capacity in the adult is about one quart; it has two openings, one towards the heart called the _cardiac orifice_, which receives the food from the œsophagus, and the other at the right or small end of the stomach, called the pyloric orifice, for the transmission of food to the small intestines. The small intestines, about twenty-five feet in length, are coiled in various directions, and terminate into the large intestine, called the colon, which is about five feet in length, and resembles in appearance a long sac divided into numerous pouches. The pancreas is a long narrow gland, situated partly behind the right side of the stomach, and within the first curve of the small intestine.