ACTION OF THE EXCISED MAMMALIAN HEART. 
239 
and by galvanometric methods bad in many cases failed to furnish this demonstration, 
and the failure is repeated by the electrometer {monophasic variation). The conclu¬ 
sion we draw from this is that in such cases the ventricles contract in their several 
parts with a synchronism such that no evidence of wave as regards the excitatory 
process is obtainable by any method we have used. Whether the synchronism 
be absolute or not, we cannot say; it does not affect the conclusion we are about to 
draw, viz., that the excitatory change must, under such conditions, be practically 
Photograph 5. 
Puppy. Two double variations in ventricle. The first is of a spontaneous contraction and indicates: 
first phase, apex negative; second phase, base negative; the second variation is caused by mechanical 
excitation of the apex, and also shows first phase apex negative, second phase base negative. The 
mechanical excitations to produce this contraction were three in number; the first two were 
ineffectual, i.e., produced no visible contraction, they are, however, visible upon the tracing, the 
apex negativity having been permanently increased by each excitation. Apex negativity remained 
permanently increased after the diphasic variation had come to an end. (Apex to H 2 S0 4 . Variation 
NS.) 
simultaneous in all parts of the ventricle, and that such simultaneity postulates the 
existence of nervous channels of conduction. What are the conditions of the difference 
in the two cases % To this question we can only answer that we have, in general, 
observed the monophasic variation during early moments after excision of the heart , 
the diphasic valuation subsequently to these earlier moments; more definite expres¬ 
sions we cannot use on account of the differences of individual hearts. We have 
further observed more than once the diphasic variation to supervene upon the 
monophasic in one and the same heart, as time advanced, without any alteration in 
the position of the electrodes (Photo. 6). As time advances, however, a diphasic may 
give place to a late monophasic variation, which is, to our mind, suggestive of a 
