671 



The effect of CaCl^, KCl and NaCl liad alread}- been deleimiiied ; 

 it only remained to examine the effect of the iSfaHCO^ concentratio7i. 



Since Ringer it has been generally assnmed that in artificial 

 transmission fluids NaHCO, is indispensable. The present researches 

 have likewise shown that it cannot be dispensed with in the 

 transmission-fluid. One of the functions of NaHCOj consists as we 

 know in maintaining a very slight actual alkalinity of the body-fluids 

 which would otherwise, owing to the continual formation of acids, 

 pass into an acid reaction. Like serum protem it acts as a buffer; 

 hence we also speak of a tampon or moderator. Besides a specific 

 HCO', -action may have to be assumed (E. Laqueur). 



It appears already theoretically that a concentration of NaHCO, 

 0.01 7o is too low to act as a sufficient buffer. We shall revert to 

 this later on, in connection with other more theoretical considerations. 



Ringer himself added 5 cc. of a 1 "/(, ]SaH0O,-sol. to 100 cc. of 

 fluid. Tyrode even used 0.1 7. of NaHCO,. But 0,02 7„ of NaHCO, 

 is the rule in Ringer's fluid. ^) That the usual concentration of 0.027o 

 of NaHCOj is too slight for frogs' kidneys could be determined ex- 

 perimentally in the following manner. 



If namely to a transmission-fluid composed: NaCI 0.6 7o' ^^^^CJO, 

 0.02 7o CaCl, 6aq 0.01 5 7„ some neutral red') is added, the colour 

 •of the indicator is orange yellow (slightly alkaline), which corresponds 

 with [H-] = 1.10"**. It is necessary to use boiled out aq. dest. and 

 to prevent the absorption of CO,. Now we need only shake this 

 fluid for a moment with air or lead it through an India rubber 

 tube and the colour turns to pink, which points to an acid reaction 

 of [HJ^I.'IO ^ If, however, one is careful in preparing this fluid 

 then one succeeds in keeping it slightly alkaline. Now if this fluid 

 is transmitted through the kidney, the latter becomes evidently acid, 

 which is manifested by the red colour it assumes and also the meta- 

 bolism products which have passed into the urine, colour the indicator 

 red after some time. We have made the oxygenation in the experi- 

 ment as intense as we could to eliminate metabolism products of 

 greater acidity as much as possible, without succeeding, however, 

 in keeping the reaction of the urine neutral. 



What is the reaction of the normal urine of the frog? 



It is not difficult to obtain it by squeezing out the bladder of 



') Gf. e.g. Bayliss: Principles of General Physiology, 1916, p. 211. 



Zwaardemaker and his collaborators also use this concentration of 0.02 %. 

 (See eg. Proceedings 1916, April 28, May 27, Sept. 30). 



2) The reader will be aware tkal the colour of this vital indicator is at 

 [H] = 1.10-7 pink, at [H-] =1.10-8 orange yellow and at [H-] = 1.10-9 yellow. 



