54 T. BRAILSFORD ROBERTSON. 



3. It occurred to me that, provided the above-mentioned as- 

 sumptions were correct, the efficacy of a saline medium in main- 

 taining the heart-beat at a normal rate should depend upon two 

 factors, namely, the reversj>ility of the chemical changes inaugu- 

 rated by it, and the value of ?t/[?'(tt -f- ?')] for the solution. Any 

 solution bringing about only reversible changes (that is, for ex- 

 ample, not containing heavy metals) and having the same value of 

 /[?'(?/ -f?')], as Ringer's solution, should be equally efficacious 

 in maintaining the heart-beat. Loeb has introduced the concep- 

 tion of Physiologically Balanced Salt Solutions. 1 It maybe that 

 as far as rhythmically contracting tissues are concerned the value 

 of ?/ [v(// 4- T')] may afford us a clue to the theoretical composi- 

 tion of such solutions. 



4. I made up a Ringer solution with the following composi- 

 tion : A r /io NaCl + ^250 KG + A'72OoCaCl , which proved to 

 be a good heart solution. The NaCl was made free from potas- 

 sium by volatilizing the KC1 out of Kahlbaum's C. P. NaCl, KC1 

 having a lower boiling-point than NaCl. The average value of 

 ?/ for such a solution can be found by multiplying the velocity of 

 each kation by its equivalent molecular concentration, and divid- 

 ing the sum of these products by the sum of the concentrations. 

 The value of uj\v(u + ?')] for this Ringer solution, calculated from 

 the values for the ionic velocities given in Landolt-Bornstein, 2 is 

 621.2 x IQ- 5 . A solution of LiNO,, NH 4 NO 3 and NaNO 3 hav- 

 ing approximately the same value for ;/'[?'(// + ?-)] is one made up 

 as follows : .i35A r LiNO 3 '-f .O3A r NH 4 NO, + .oiA r NaNO 3 the 

 value of ///[?'(// + ')] (calculated from the table of ionic veloci- 

 ties quoted above) is 628 x io~'\ This forms an excellent heart 

 solution ; twenty-three variations of this solution were tested, 

 keeping the concentration of the LiNO 3 constant, and varying 

 that of the NH.NO, and' NaNO,. In solutions i-c. the LiNO, 



4 J o -^ ."i 



and NaNO 3 were kept at .135^ and .01 5 A 7 respectively, and the 

 NH 4 NO 3 varied from .03^ to 04 5 A 7 , increasing in concentration 

 in each solution from i to 5 by .OO5A\ In solutions 6-9 the 

 concentrations of the LiNO.^ and NH 4 NO. 5 were kept at .135^ 



1 American Journal of Physiology, Vol. III. (1900), p. 431, "Studies in Gen- 

 eral Biology," Decennial Publications of the University of Chicago, Vol. II., p. 590. 



2 Physikalische-Chemischi Tabtllen, 1905. 



