1883.] 



Experiments upon the Heart of the Dog. 



271 



giving the citron spectrum, and no sooner had the exquisite sensitive- 

 ness of this spectrum test forced itself on my notice than I sought for 

 yttrium in other minerals. The facts which I had noticed in con- 

 nexion with the variation of the appearance of the citron spectrum, 

 according to the quantity of yttrium present, showed that it might be 

 possible to devise a process for the rough quantitative estimation of 

 yttrium, and after several experiments a spectrum test was devised 

 sufficiently delicate to detect one-millionth part of yttria in a mineral. 

 A table is given showing the results of this quantitative spectrum 

 analysis, from which it is seen that amongst other substances a specimen 

 of coral! contains one part of yttrium in 200 parts ; strontianite, one 

 part of yttrium in 500- parts ; chondrodite, from Mount Somma, one 

 part in 4,000 ; calcite ? one part in 10,000 ; ox bone, one part in 

 10,000 j an earthy meteorite (Alfianello), one part in 100,000; and 

 tobacco ash, one part in 1,000,000. 



The following Paper was read : — 



"Experiments upon the Heart of the Dog' with reference to 

 the Maximum Volume of Blood sent out by the Left Ven- 

 tricle in a Single Beat, and the Influence of Variations in 

 Venous Pressure, Arterial Pressure, and Pulse Bate upon 

 the Work done by the Heart." By William H. Howell, 

 A.B., Fellow of the Johns Hopkins University, and F. 

 Donaldson, Jr., A.B. Communicated by Dr. M. Foster, 

 Sec. R.S. 



(Abstract.) 



Owing to the indirectness of the methods hitherto used for 

 estimating the quantity of blood pumped out from the left ventricle 

 at each systole, this important factor in all calculations of the work 

 done by the heart has never been satisfactorily determined. Of the 

 later physiologists who have investigated the subject, Volkmann and 

 afterwards Vierordt, from calculations based upon the mean velocity 

 of the stream of blood in the unbranched aorta, obtained the fraction 

 T ^o as representing the ratio of the average weight of blood ejected 

 at each systole of the left ventricle to the weight of the whole body. 

 Pick, from data obtained by placing the arm in a plethysmograph, and 

 estimating the velocity of the stream of blood in the axillary artery 

 from the increase in volume of the whole arm at each systole of the 

 heart, arrived at a much smaller fraction, about X ^ QQ 1 for the ratio 

 between the weight of blood thrown out at each systole and the body- 

 weight. 



