The blood pressure may be sufficient, or even increased if arteriosclerosis is present, although the rise of the sphygmograph tracing is not so high as normal. If the pressure in the aorta is sufficient from the amount of blood forced into it, the coronary arteries receive enough blood to keep up the nutrition of the heart muscle.

This prolonged rest or diastole of the heart allows the circulation in the coronary arteries to become normal, and the nutrition and muscle tone of the heart improves. Digitalis also increases the blood pressure, not only by improving the activity of the heart, but also by causing some contraction of the arterioles.

The muscular substance of the heart itself is supplied with nourishment by two little arteries called the coronary arteries, which start from the aorta just above two of the semilunar valves. The longest route a portion of blood may take from the moment it leaves the left ventricle to the moment it returns to it, is through the portal circulation.

Pseudo-angina. In connexion with angina pectoris, a far more common condition must be mentioned that has now universally received the name of pseudo-angina. This includes the praecordial pains which very closely resemble those of true angina. The essential difference lies in the fact that pseudo-angina is independent of structural disease of the heart and coronary arteries.

The wall of the right ventricle may now be raised and the cavity exposed. Now cut through the middle of the loosened ventricular wall from the apex to the middle of the right auricle, laying it open for observation. Observe the openings into the auricle, there being one each for the vena cava superior, the vena cava inferior, and the coronary vein.

The "cannon bone" answers to the middle bone of the five metacarpal bones, which support the palm of the hand in ourselves. The "pastern," "coronary," and "coffin" bones of veterinarians answer to the joints of our middle fingers, while the hoof is simply a greatly enlarged and thickened nail.

The heel of the horse is the part commonly known as the hock. The hinder cannon bone answers to the middle metatarsal bone of the human foot, the pastern, coronary, and coffin bones, to the middle toe bones; the hind hoof to the nail; as in the fore-foot. And, as in the fore-foot, there are merely two splints to represent the second and the fourth toes.

Such a circuit in the liver is called the portal circulation, and another in the kidneys is termed the renal circulation. To some extent the blood supply to the walls of the heart is also outside of the general movement; it is called the coronary circulation. Body in general. 2. Lungs. 3. Kidneys. 4. Liver. 5. Organs of digestion. 6. Lymph ducts. 7. Pulmonary artery. 8. Aorta.

From the splenic branch which passes into the pancreas, and from the upper part, arise the posterior coronary, gastric, and gastroepiploic veins, all of which are distributed upon the stomach in numerous branches and twigs, just as the mesenteric vessels are upon the intestines.

It is a disturbance of the heart which most frequently attacks men, probably more than three fourths of all cases of this disease occurring in men; in a large majority of the cases the coronary arteries are diseased. Various pains which are not true angina pectoris occur in the left side of the chest; these have been called pseudo-anginas. They will be referred to later.