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Transactions of the Boyal Society of South Africa. 
izable stimulating electrodes are applied on the ventral surface at the apex. 
The left electrode is placed on the ventral surface about 2 mm. from the 
point of stimulation, and the right electrode is applied to the mid-point 
of the base on the ventral surface. The break induction shock is evident 
on the curve, and the response appears to commence with the downward 
deflection, which indicates negativity of the left (here the proximal) 
electrode 
In Fig. 12a both electrodes are applied close to the point of stimulation 
at the apex separated from each other by as short a distance as possible, 
and the stimulation is given mechanically by the touch of a glass point. 
The first movement of the string is a slight positive — upward — deflection 
preceding the downward deflection, which indicates negativity of the left 
Fig. 11. 
(here the proximal) electrode. In Fig. 12b the electrodes, retaining their 
relative position to one another, have been transferred to the middle of the 
base, and the apex is again stimulated mechanically. The positive deflec- 
tion Q is here quite distinct. 
In Fig. 13 we have a series of responses obtained from the isolated 
quiescent tortoise ventricle stimulated by break induction shocks when the 
application of the stimulus is transferred from point to point along the 
transverse diameter of the ventricle. The two leading-off electrodes are 
placed on the dorsal surface, the right at the left margin and the left 
at the right margin, separated from each other by a distance of 50 mm. 
The wicks of the non-polarizable stimulating electrodes are placed on the 
dorsal surface 5 mm. from the right electrode, and response 1 is recorded 
