Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Chapter III Variations In The Distribution Of The Coronary Arteries AS has been indicated, the coronary arteries are rather prone to variations. It is this disposition to variat1ons wh1ch renders their description somewhat artificial and rigid. There appears, however, to be one typical variation which is rather constant and which will be described here. For the reason that the other possible variations assume clinical and pathological interest, a table classifying a statist1cal analytical study of the course and character of the coronary arteries will follow. If one makes a review comparing the general characteristics of the average distribution of left and right coronary arteries, one is struck by the fact that the main stout ramus descendens anterior of the left coronary artery has its counterpart in the ramus descendens posterior of the right; furthermore, that the left coronary artery seems to trespass on the anterior surface of the right ventricle and falls somewhat short of supplying completely the left ventricle posteriorly. The main scheme, therefore, in so far as the ventricular supply is concerned, seems to be a sort of twisting of the vessels in a direction from left to right anteriorly and right to left posteriorly. An examination of what is termed the typical variation (Fig. 7) shows, first of all, that both the anterior and posterior rami descendentes come from the left coronary; secondly, that the rather aborted ramus circumflexus sinister, which is F1e. 7.—Roentgenogram of a typical variation in coronary artery dirtribution. seen in the normal heart, is represented here by a very typical and characteristic circumflex branch which imitates accurately that found normally on the right side. Thus, even the branches, which have been described as ...