American journal of physiology . through cotton wool. From 25 to 100 cc. of extractsmade in this way were added to 4 litres of Lockes solution contain-ing defibrinated blood from a cat which had not been subjected tostimulation. The first experiment served as a control to determineany possible influence of the extract of resting muscle. Experi-ments in which the effect of extracts from tetanized muscle wasstudied (III and IV) were further controlled by similar extractsfrom resting muscle previously perfused through the same it was desirable to employ in these experiments hearts fro
American journal of physiology . through cotton wool. From 25 to 100 cc. of extractsmade in this way were added to 4 litres of Lockes solution contain-ing defibrinated blood from a cat which had not been subjected tostimulation. The first experiment served as a control to determineany possible influence of the extract of resting muscle. Experi-ments in which the effect of extracts from tetanized muscle wasstudied (III and IV) were further controlled by similar extractsfrom resting muscle previously perfused through the same it was desirable to employ in these experiments hearts fromanimals which had been anesthetized lightly and for a short periodof time, and also to have fresh extracts or blood for perfusion, twoor more animals were used for each experiment. Fatigued musclefor extraction was obtained by anesthetizing an animal with ether,cutting the spinal cord in the lumbar region, and stimulating thedistal end with a faradic current for periods of from three quarters 304 M. S. Petersen and H. S. Gasser. Figure 1. Experiment I. Shows the absence of effect on rate or size of beat fromchanging from normal perfusion to a perfusion solution containing extract ofresting muscle (i cc. of extract to 40 cc. Lockes solution containing defibrinatedblood). In this and succeeding figures the lower line marks the time in intervalsof one second. The upper line is a suspension curve of the ventricles, the up-stroke of which represents systole. All records read from left to right. The markX indicates the change from normal perfusion to perfusion with the extract.
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