Activity of the Vasomotor Centers

The hind limb of the cat connected to the body by its nerves alone, and perfused with Krebs ' solu-tion is a simple method of studying the reactions of the vasomotor mechanisms. The central action of epinephrine and a failure of the center as a result of prolonged hemorrhage or anoxia have been shown. OUR knowledge of the vasomotor mecha-nism in the past has for the most part been obtained by studying the blood pressure and blood flow in the peripheral vessels by means of plethysmography or flow meters before and after section of the vasomotor nerves. A small number of workers have perfused isolated or-gans connected only by nerves. More recently a number of workers have perfused various parts of the body from another animal or by pumps. These methods are obviously very costly and although possible for special projects are not suitable for the routine studies such as the action of drugs. In the present investigations, the innervated hind-limb perfused with Krebs ' solution at 37 C. gives identical results to those obtained by other more complicated and expensive methods. I t offers also a simple method for the study of the action of the central vasomotor mechanisms. In this paper a number of the classical ex-periments are reported to show the general value of the method, and in doing so several new points have been brought out and detail added. For simplicity the term "vasomotor centers " is used, but it is to be understood that these include all the central mechanisms in-cluding synapses in sympathetic ganglia. METHODS The observations were made on cats anesthetised with chloralose (60 mg./Kg. body weight), the blood pressure being recorded in the carotid artery. One hind leg was perfused through the femoral or the iliac artery, or more commonly through the abdominal aorta because of its convenient size. All branches below the cannula and down to the femoral artery were tied. All veins were also tied of