The fast self-sustained activity of mammalian auricular muscle

670 THE

AMEKIC:lN HEAKT JOUKNX FAST SELF-SUSTAINED ACTIVITY OF MAMMALIAN AUKlCULAR MUSCLE.-A. ROSENWUETH, M.D., ;\ND J. GAKC~.\ RL\~os, M.D., MEXICO D.F., MIXICO.

In isolated auricular appendices, fast nonstimulated discharges follow rapid The frestimulation after acetylcholine or carbaminoylcholine are administered. quency is related to that of the stimuli. Below a critical frequency of stimulation (approximately 20 per second), no automatic discharges ensue. The activity requires the presence of the choline ester. There are more discharges with larger than with smaller doses. Further injections during an episode prolong it. It is longer when acetylcholine is administered after Prostigmine, and longer for carbaminoylcholine than for acetylcholine. Atropine abolishes the phenomenon; curare does not. The discharges end suddenly. The terminal frequency (about 20 per second) is lower than the refractory period requires, for after activity ceases, The activity stimulation elicits faster discharges, whrch may outlast the stimuli. is usually regular, but may become irregular, as if successive impulses started at different points or several regions were discharging independently. It is probably not maintained by a circus movement; it persists in an area smaller than a square centimeter. It differs from the slow type of self-sustained activity both in frequency and in requiring the presence of an acetylcholine-like agent which inhibits the slow activity. NORMAL VALUES OF THE ARTERIAL PRESSURE AND FREQUENCY OF ARTERIAL HYPERTENSION IN HIGH ALTITUDES.--ANDRES ROTTA, M.D., ,~ND ARTEMIO MIRANDA, M.D., LIM.~, PEW. In a town of about 7,000 inhabitants and at 13,850 feet above sea level (Morococha, Peru), an investigation was conducted to detect cases of arterial hypertension. At the same time the blood pressure of 1,878 healthy individuals between 18 and 71 \-ears of age was measured. Among this group there were fifty-three Caucasians (North Americans, Italians, Spaniards, and Peruvians), dwellers of high altitudes for many years; the rest were native Indians. The following results were found: 1. Neither in the investigation nor in the direct examinations were cases of arterial hl-pertension found. 2. The systolic arterial pressure is lower in men at high altitudes than in those at sea level, (mean pressure, 108 mm. Hg); the diastolic arterial pressure is higher than at sea level, (mean pressure, 88 mm. Hg). 3. Since the few nonIndians showed no difference from the natives, either in the systolic or in the diastolic pressure, it may be concluded that the figures obtained have nothing to do with the racial characteristics and that chronic anoxia does not influence arterial pressure. THE

SYSTOLIC DISEASE.-D. FRANCE.

EXPANSlON ROUTIER,

OF THE LEFT AURICLE M.D., AND R. HEIM DE BAISC,

IN MITRAL M.D., PAWS,

The radiologic examination of patients with mitral disease permits recognition in the most advanced cases of an expansion of the left auricular contour during ventricular systole. Radiokymography gives more precise information regarding this phenomenon, which can be observed either in the anteroposterior position when the left auricle extends to the right border of the heart, or in the right anterior oblique, left lateral, or left posterior oblique position, when the tilled esophagus follows the auricular outline closely. A description is given of the radiokymogram and of the expansion observed. Interpretation: The left auricular distension during ventricular systole is evidence of auriculoventri-