TRANSACTIONS OF THE SECTIONS. 457 



been able to observe, in the human heart than in that of any 

 other animal. 



Mr. Carlile has ascertained, also, that the ventricles assume 

 this form during their contraction, after they have been sepa- 

 rated from the auricles by a ligature, and even after they have 

 been removed from the body, and placed in a vessel of tepid 

 vi^ater, or held upon the hand, the auricles having been pre- 

 viously cut off; in all which cases the peculiar motions which 

 accompany their contraction and relaxation were observed to 

 recur as long as their power of moving remained ; proving that 

 the beat of the heart is produced altogether by the action of 

 the ventricles during their systole, and that in these, as in all 

 other muscles, the peculiar forms assumed during their con- 

 traction depend upon the relation, as to length and position, of 

 the fibres of which they are composed. 



3rd. The arterial pulse, which is produced by the jet of 

 blood sent from the left ventricle into the aorta during its 

 systole, has been stated by Bichat and many other writers to 

 be synchronous throughout the whole arterial system. But 

 the experimenter can ascertain in his own person that the pulse 

 is successive at different distances from the heart. If the hand 

 be placed over the region of the heart, and the radial artery be 

 felt at the same time, an interval will be distinctly perceptible 

 between the beat and the pulse ; and if the anterior tibial artery 

 be substituted for the radial, the interval will be found still 

 greater. Repeated observations of this kind show that the in- 

 tervals of time between each beat of the heart and the corre- 

 sponding pulse in different parts of the body are proportioned 

 to the distances measured along the arteries, from the heart to 

 the respective parts; and a knowledge of this fact leads, without 

 further anatomical inquiry, to the conclusion that the beat of 

 the heart is coincident with the ventricular systole. For, as 

 the intervals of time betAveen the beat and pulse are propor- 

 tioned to the distances from the heart to those parts where the 

 pulses are felt, it follows that when the distances become eva- 

 nescent the intervals of time will also vanish. Consequently, at 

 the origin of the aorta the pulse will coincide as to time with 

 the beat of the heart ; but the pulse at the origin of the aorta 

 is necessarily synchronous with the ventricular systole, by which 

 the blood is driven into that artery ; and therefore the beat 

 of the heart will coincide with the ventricular systole, a conclu- 

 sion which agrees with that drawn from positive experiment. 



The proportion which exists in the pulse between the in- 

 tervals and distances is dependent upon the elasticity of the 

 arteries. 



