Physiology. — "A Contribution regarding the Shifting of Radio- 

 active Equilibria under the Injiiience of Fluorescein" . Bj 



Prof. H. ZWAARDEMAKKH. 



(Communicated in the meeting of Sept. 29, 1917). 



In an earlier paper ^) I demonstrated that tlie diffusible potassium 

 in the circulating fluid of surviving organs of cold-blooded animals 

 could be replaced bj the ions of other radio active elements. This 

 should then be done in approximately aequiradio-active quanta. It 

 deserves notice that with summer- frogs the dosage may be much 

 smaller than with winter- frogs, which accounts for the difficulties 

 workers have encountei-ed in summertime with this laboratory 

 animal, especially in quantitative studies. In the past months we, 

 my co-workers and myself, succeeded in determining the ratios for 

 the Kroneckered ventricle. We first lowered the calcium content of 

 the artificial circulating fluids, and when this turned out unsuccessful, 

 it was raised. An amount of 250 mgrms CaOlj (without water of 

 crystallization) per Liter proved efficient. 



It will be advisable to use distilled water in vitro. The osmotic pressure 

 was maintained by 6^ — 7 grammes of sodium chloride and the reaction 

 was made slightly alkaline by adding 200 mgrs. NaHCOj. This 

 solution is prepared the day before and can be kept (not too long 

 though) in bottles of ordinary glass. Examined on potassium it must 

 not contain more than 1 mgrm per Liter. 



In order to ascertain whether the heart is normal, first a normal 

 Ringer's mixture is perfused. In winter this mixture should preferably 

 contain da 100 mgrms of KCl per Liter. It now appears that in 

 summer-time we have to go down to 20 — 50 mgrms, else the hearts 

 will refuse to beat. If by chance the usual Ringer's mixture of the 

 laboratory should have been used for the preliminary experiment, 

 the hearts will perform a few beats, then stop, in order to resume 

 pulsation for a short time, when measures have been taken to wash 

 off the superfluous potassium. By adding a large amount of calcium 

 to the fluid, the toxicity of potassium may be lowered. 



With 250 mgrms CaCl, per Liter the summer doses range: 



1) Proceedings Royal Society Vol. XIX p. 633. 



