130 



SCIENCE. 



[N. S. Vol. V. No. 108, 



facts : A fall in the volume of the coronary 

 circulation, e. g., 73 %, caused a fall in the 

 force of the heart beat of 49 %, while the 

 frequency was altered but 9 % . Restoring 

 the volume of the coronary circulation re- 

 stores the force and frequency of the heart 

 beat. The change in force follows the 

 change in blood supply immediately. These 

 and other related observations are about to 

 be published in the Journal of Experimental 

 Medicine, by J. B. Magrath and H. Kennedy. 



Miss Hyde has studied by the same 

 method the effect of distention of the heart 

 on the volume of the coronary circulation. 

 Distension of the left ventricle, i. e., mak- 

 ing a constant pressure in the ventricle 

 through a side branch of the membrane 

 manometer tube, diminishes per se the vol- 

 ume of the coronary circulation. Disten- 

 tion acts further as a stimulus to the cardiac 

 muscle, causing the ventricle to beat more 

 strongly. Strong contractions of the ven- 

 tricle cause an increase in the volume of the 

 coronary circulation. If the ventricle, hav- 

 ing been distended, is placed again at at- 

 m^ospheric pressure, the force of contraction 

 is much diminished. 



Dr. Porter also showed curves recording 

 the diminution in coronary flow occasioned 

 by stimulation of the peripheral end of the 

 vagus nerve. Increase in coronarj' circula- 

 tion follows stimulation of the cervical 

 sympathetic. These results indicate vaso- 

 constrictor fibres in the vagus and vaso- 

 dilator fibres in the sympathetic. 



Later Dr. Porter demonstrated his method 

 of isolating the cat's heart for purposes of 

 physiological investigation. 



On the duration of cardiac standstill ivith dif- 

 ferent strengths of vagus stimulation. T. 



HOTTGH. 



A stimulus of uniform strength was ob- 

 tained by the use of a storage battery in 

 the primary circuit, which was interrupted 

 by the revolutions of a small electric motor 



run at a constant rate of speed; the strength 

 of stimulus was varied by changing the re- 

 sistance in a German silver rheochord 

 placed in the primary circuit. It was 

 found that when the inhibitory impulses, 

 obtained by stimulation of the vagus nerve^ 

 are just strong enough to bring the heart 

 of the dog to rest, the duration of stand- 

 still is not so long as with stronger stimuli ; 

 but that a very slight increase of stimulus 

 above this point produces a stand- still 

 which is not lengthened by any further 

 strengthening of the inhibitory impulses. 

 The conclusions drawn from previous work 

 on the same subject (Journal of Physiol- 

 ogy, XVIII., 190) are, therefore, correct. 



Some experiments on the relation of the inhibi- 

 tory to the accelerator nerves of the heart.. 

 R. Hunt. 



Some of the effects of stimulating the two 

 nerves separately were first described; then 

 the result of stimulating the nerves simul- 

 taneously. The experiments show that,, 

 contrary to the commonly accepted opinion 

 of Baxt, the inhibitory and accelerator 

 nerves are to be regarded as purely antag- 

 onistic; that the result of stimulating the 

 two together is approximately the algebraic 

 sum of the effects produced by stimulating 

 them separately. In no case did one nerve 

 completely overcome the effect of the other, 

 though the two were stimulated for periods 

 as long as twelve minutes. The experi- 

 ments were performed upon dogs and cats. 



Exhibition of plethysmographic curves obtained 

 during sleep, with remarks. W. H. How- 

 ell. 



Prof. Howell exhibited plethysmographic 

 curves showing the changes in volume of 

 the hand and wrist during the period of 

 normal sleep. The apparatus was so ar- 

 ranged as to register the actual changes in 

 volume without altering the pressure upon 

 the parts under observation. The curves 

 showed that from the beginning of the at- 



