A new method of crossed circulation

The method of crossed circulation originally introduced by Frédéricq in 1890 (1) and subsequently used and improved by himself (2), Hédon (3), Foa (4), Leroy (5), and Bazett and Quinby (6), consists in a crossed anastomosis between two large arteries, usually the carotids, or, in the case of the last two authors, the ascending aorta. Crile (7) and Janeway and Ewing (8) modified the original method by making a crossed arterio-venous anastomosis. The method was used for the study of the relative importance of chemical and nervous factors in the control of respiration and circulation. More recently, Tournade and Chabrol (9) (10) made an anastomosis between the suprarenal vein of one dog and the jugular vein of another. The value of all these methods in their original form, and in their modifications, is greatly diminished by the variable amount of bleeding of one animal into the other, which occurs when the blood pressure in the two animals is different. This source of error is so great that only those experiments in which the blood pressures in both animals show opposite changes can be taken as really valid. These results must, however, also be distorted because there is always present the tendency for the blood pressure to equalise. The ideal arrangement of a crossed-circulation experiment would seem to be such as to have complete control over the circulating fluid at any time of the experiment, so as to be able to produce changes in one animal without affecting the rate of the interchange of the blood between the two. The method described in this communication gave, considering the difficulties of the experiments, satisfactory results. It has already been applied with success in certain experiments (11).