A Single Coronary Artery.

Many different anomalies of the coronary vessels have been observed. The minor varieties are quite common, but the more gross forms are relatively rare. An example of one of these gross forms is given in this paper. The variations may be divided into a number of groups: (1) in origin, (2) in number, and (3) in distribution and size. Anomalies in origin are due to the vessel starting abnormally: (a) from the common arterial trunk, and this is often found where there are other associated disturbances of development ; (b) from the pulmonary artery, when changes develop secondarily both in the artery and in the myocardium, changes that depend directly on this aberrant origin of the vessel ; and (c) from the aorta, at a variable distance above the level of the cusps. Anomalies in the number of vessels are rather more common and may be unusual by a reduction or by an increase in the number ; thus on the one hand there may be only one artery arising from the aorta, or on the other hand there may be three, four, or more vessels. As far as their supply to the myocardium is concerned they merely take the place of the normally occurring vessels in most instances. Thus a single artery is usually much larger and gives a supply to the whole of the heart, whereas an increased number of vessels are individually smaller and correspond in their distribution to one or more of the branches of the normal arteries. Anomalies in distribution and size depend to a considerable extent on, and run pari passu with, anomalies in the number of main trunks.