The committee's first report, published in Circulation for June 1953, recommended a terminology and certain conventions for recording ballistocardiograms of the type then in use. However, it soon became apparent that the committee's work was far from complete.Increasing knowledge of ballistic theory soon began to throw light on the relations of records secured by various instruments to one another, and a rapid advance in instrumentation began to provide records related to, but often not identical with, those which had been provided with a standard terminology by the committee in its first report. Accordingly, the committee has continued its labors to provide the rapidly advancing field with a uniform terminology.While they were thus engaged, attention was called to the fact that the designation of spatial axes previously recommended for vector ballistocardiograms differed from that which had been recommended for electrocardiograms by another committee of the American Heart Association. The advantages of a common system for designating spatial axes were obvious to all. Accordingly, as the electrocardiographic usage had priority and as little had been published in the field of ballistocardiographic vectors the committee voted to withdraw their original recommendation and substitute one conforming to that in use by electrocardiographers. In the present communication this new convention is also set forth.All members of the committee have shared in the deliberations and taken part in the decisions which form the basis of this report; but so much of the larger proportion of the actual work fell on Dr. Scarborough and Dr. Talbot that it was agreed without dissenting vote that only their names should appear as authors. This report has the endorsement of the committee as a whole, and the terminology it suggests is recommended as the official terminology of the American Heart Association.
It has been fairly well established (1-12) that a mechanism for wave length discrimination is a part of the visual equipment of diurnal birds. Since these researches leave something to be desired in the way of completeness, it was thought well to repeat the work controlling brightness and other secondary criteria, as well as possible, by means of colored cards, and, inasmuch as the pigeon showed evidence of responses which could best be interpreted in terms of trichromatic vision, to extend the investigation using spectral stimuli of known wave length and objectively controllable intensity.Pigment stimuli. The apparatus was the same as that used by us in our experiments on the rats (18). It was rather difficult to tame the pigeons, but as soon as they became willing to jump, the actual training (conditioning) could be accomplished in 10 to 100 trials.The stimuli were the same series of gray, red, blue and green cards as used with the rats (18). Each series varied from a deep, intense color to a barely perceptible tinge of the same color through admixture of white. Ordinary dichromatic (colorblind) medical students were hopelessly lost in sorting the reds from the greens of these series, though they had some success with the grays and more still with the blues. The pigeons were systematically trained to jump toward one of each of several of the pairs of colors as indicated in the table.After the pigeon had been trained (training jumps in table 1) to select the blue, say, as against the gray, the intensity of each
During the past ten years there have accumulated in this laboratory a large number of records of the arterial pressure pulses taken with the Hypodermic Manometer (4). These are faithful records of the changes in the pressure of the blood in various arteries of man and of other animals. The form of the pressure pulse curve is quite variable. Some of the types are drawn roughly to scale in the figures presented herewitOh, but, there are many intergrading examples which can not be shown for lack of space.It is the purpose of this paper t,o describe the manner in which these typical patterns tlake form and to present a simple hypothesis that will account physically for t,he variations seen in the pressure pulses in different arteries and under different? conditions.The simplest pulse form is that seen in very small animals such as the mouse, canary, frog or turtle (1). During early systole the ejection from the heart is rapid, blood is coming into the arterial tree faster than it is leaving through the arterioles and the pressure in the arteries rises abruptly.Later the rate of ejection falls, the arterial pressure rise continues but becomes less abrupt. Toward the end of systole there is a balance between the rate of ejection and the rate of arteriolar drainage. The curve is then horizontal. An actual decline in the curve is sometlimes seen during late systole, when ejection falls to a rate that is less than arteriolar drainage.During diastole the curve is a perfectly smooth fall of pressure with time. falls faster at first when the pressure is high. ItBlood drains out of the arterioles more rapidly and each unit of blood leaving the arterioles makes a greater pressure diff'erence when the pressure is high than when the pressure is low.This smooth pressure curve is the simple consequence of filling and emptying of the aiterial compression chamber. However it is seen only in small animals. The t,inv arteries of these creatures respond so quickly that tlhey follow faithfully t,he pressure changes which are produced by the heart.In ordinary laboratory animals such as the dog and in man the form of the pressure pulse is much more complex. Superimposed upon the first described filling and emptying curve are waves of arterial origin. This is because the mass of the arberial blood column is so large and the arterial walls are so distensible that the action of the heart sets up oscillations of pressure in the artery that are reflected back and forth over its length as they gradually damp out. The natural period of these waves varies directly with the time it takes the pulse wave to be transmit,ted from one end of the artery to the other and their amplitude depends upon t.he abruptness of the initial upstroke of the pulse and the sharpness with which reflect.ion takes place at the end of the artery. These waves, therefore, 235
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