Summary. In the present paper we report on an investigation in which the amount of hemoglobin determined after the method of SJÖSTRAND (1948) in a number of athletically trained men and women has been compared with that in an average group of the respective sexes. The athletically trained men and women showed considerably higher amounts of hemoglobin and blood volumes than the average material. On the whole, the best trained men deviated by 41%, and the women by 44% from the reference material. In three men and one woman the amount of hemoglobin was determined just before and immediately after a skiing tour in the mountains. The figures were 10–19 per cent higher after the training than before. In a patient who had been confined to bed for a considerable length of time (owing to fracture of the leg) the amount of hemoglobin was determined repeatedly. It showed a successive decrease, amounting at its maximum to 15 per cent of. the original figure. The amount of hemoglobin and blood volume seems accordingly to vary with the degree of physical training. The costs of the investigation have in part been defrayed by a grant from the Therese and Johan Andersson Memorial Fund.

"The chief value of the recorded heart sound is the possibility of accurately timing its occurrence in relation to the events of the cardiac cycle." This is even truer to-day than when Lewis first stated it (1915), because methods for recording events in the cardiac cycle have become more precise. In spite of this, there is still lack of agreement on the origin of the heart sounds. The causes of the second heart sound have been clearly defined, but there is a divergence of opinion on the origin of the major components of the first heart sound. On auscultation in young people the first sound may be heard to be narrowly split at the lower left sternal border. This splitting is widest and therefore most easily heard at the end of expiration (Potain, 1866). The origin of these two components has been attributed by some to closure of the auriculo-ventricular valves followed by opening of the semilunar valves (Orias and Braun-Menendez, 1939;Rappaport and Sprague, 1942;Luisada et al., 1949;Nazzi et al., 1954). Others have suggested that it is due to asynchronism in contraction of the ventricles (Wolferth and Margolies, 1945), and so to closure of the mitral valve followed by closure of the tricuspid valve (Leatham, 1954). Much of the evidence for these views has been obtained by relating the components of the heart sounds to dynamic events in the cardiac cycle by the use of reference tracings. Phlebograms and indirect carotid artery tracings have been mainly used for this purpose but these have the disadvantage that an arbitrary time interval has to be allowed for pulse wave transmission when assessing results.The present investigation has been undertaken to study the nature of the first and second heart sounds and to relate their components to events in the cardiac cycle by the use of synchronous border electrokymograms. These tracings represent volume and positional changes of the heart chambers and the great vessels during the cardiac cycle. Positive waves indicate outward movement and negative waves indicate inward movement of the heart borders. These tracings have the advantage of eliminating the arbitrary time factor for pulse wave transmission. METHODSIn the first part of the investigation phonocardiograms were taken, using the Elmqvist sixchannel Klinik recorder, with three different frequency responses. These are designated high frequency, medium frequency, and low frequency according to the degree of attenuation of low frequency vibrations in each; the high and medium frequency tracings are similar to the logarithmic phonocardiogram of Rappaport and Sprague (1942) in their frequency response. Within the range of the heart sounds and murmurs the medium frequency channel has a pattern in its frequency response similar to the human audiogram; it thus represents the heart sounds as they are heard through the stethoscope. The low frequency tracings represent rather lower frequencies than are ordinarily heard through a stethoscope. Recordings were taken routinely from the apex, the fourth and second left intercosta...

Summary. By determination of the total amount of hemoglobin and the blood volume estimated on that basis, in a material of children, women and men, including athletes a very marked correlation, + 0.82 and + 0.90, respectively, was found between the amount of hemoglobin and the pulse rate during work—or the work at which the pulse reaches a level of about 170 beats per minute. This indicates that there is a close correlation between the total blood volume and the stroke volume during work. In 12 persons (among the adults) with different amounts of hemoglobin, the heart volume was determined during the performance of a varying amount of work on the bicycle ergometer. In one group of the tested persons the heart volume diminished only slightly up to a pulse rate of about 150 beats per minute, but afterwards more rapidly. In another group the heart volume diminished in proportion to the increase of the pulse rate. The first‐mentioned group consisted of individuals of average build, the latter of men of more leptosomatic type, with a small amount of hemoglobin in comparison to body height. When the movements of the left ventricular and of the aortic walls were recorded during the different cardiac periods with electrokymography, it was found that the systolic emptying of the left ventricle greatly increased during work, although the heart volume remained unchanged or was actually less than during rest. It was also shown with the same technique that there was a parallelism between the change in the heart volume during work and the filling of the left ventricle. There seems to be no direct correlation between the heart volume and the stroke volume in the same individual, an assumption, which might be expected if the stroke volume were regulated in accordance with Starling's heart law. These findings are discussed and a new hypothesis in regard to the regulation of the blood circulation and the blood distribution is advanced in order to explain the results found in normal man.

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Summary. In a material composed of children, women and men, including athletically trained men and women, the amount of hemoglobin and the blood volume estimated on the basis of the amount of hemoglobin have been placed in relation to the pulse rate, to the pulse rate/standard metabolism ratio estimated by and to the heart volume, determined roentgenologically on a subject in prone position. There is a clear correlation between the amount of hemoglobin and the pulse rate during rest. The correlation is brought out still more clearly if the amount of hemoglobin is pulse rate/standard metabolism placed in relation to the ratio which may be taken as a reference standard for the stroke volume during rest. The amount of hemoglobin and, to a still somewhat higher degree, the blood volume show a very close correlation to the heart volume determined roentgenological^ on a subject in prone position. The correlation coefficient for children, women and men is about 0.90. Broadly speaking, the figures for children, women and men, the athletically trained included, fall along the same regression line. The results serve to explain in a simple way the varying values for the resting pulse rate and heart volume, found in children and adults, women and men, and the physically trained and the untrained, respectively. It seems thus that the larger heart volume in healthy, athletically trained persons could be entirely attributed to the increased blood volume in connection with physical training. The regulation of the blood distribution (in heart, lungs and systemic circulation) is discussed with due regard to the results obtained. The costs of the investigation have been partly defrayed by a grant from the Therese and Johan Andersson Memorial Fund.