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such a manner that a high free [Ca] cannot arise, it is possible to 
investigate the influence of the [H') separately. 
It appeared already in the above-mentioned perfusions with NaCl 
0,6 °/,, KCI 0,02 °/,, CaCl,.6aq 0,015 °/,, that the [H') must be kept 
within rather narrow limits. 
When a bufter-system exists (NaHCO, + CO), the [|H] may vary 
within the limits of this system, as appears from the following 
experiments: 
a. Perfusion with NaCl0,5°/,, NaHCO, 0,28°/,, KC1 0,020°/,, CaCl, . 
Gaq 0,015°/,, Pm =8,6; there are strong spontaneous peristaltic 
movements; vagus-irritability at a coil-distance of 7.5 em. Then the 
same liquid but now with CO, passed through until Py — 7,1; the 
stomach becomes limp in 10 minutes and can no longer be in- 
fluenced by vagus-irritation. 
6. Perfusion with NaCl 0,5°/,, NaHCO, 0,28°/,, KCl 0,02°/,, CaCl, . 
6 aq 0,015°/,, Py—8,6; irritability at a distance of 8 cm., spon- 
taneous contractions. Then Py= 8,3, constant irritability at 10 ¢m.’s 
distance; spontaneous contractions of stomach. Then Py=— 7,7; 
irritability at 14 em., spontaneous rapid peristalsis. Then Py = 7,3; 
irritability at 14 em, stomach contracted spastically. Then Py == 7,1; 
stomach not irritable, spontaneous movements have disappeared. Then 
Py= 8,6; after 10 minutes’ vagus-stimulation at 8 em. spontaneous 
movements of stomach. 
This last survey is an example of many similar experiments, from 
which it appears that the slight [H’] fluctuations do not let the 
vagus-irritability disappear but certainly influence it. 
The actions of the H' and the Ca“ cannot be separated here, 
because their quantities are directly dependent on each other and 
because in general the colloid-action of the Ca'-ions depends on the 
H-ion-concentration which is present. The balancing effect of Ca’~- 
ions can be indicated only with one definite H’-ion-concentration. 
The fact that an alteration of the Ca’-ion-concentration in itself 
induces a variation of the vagus-irritability, is shown by the last 
series of experiments which correspond for the most part to condi- 
tions as they occur physiologically and pathologically. 
5. The influence of the NaHCO,-concentration. 
When the NaHCO,-degree of a liquid is moditied systematically, 
the H-ion-concentration remaining constant, one obtains likewise a 
