ACTION OF THE EXCISED MAMMALIAN HEART. 
251 
Table I. —Abstract of Galvanometer Experiments—(continued). 
Experi¬ 
ment. 
Date. 
Animal. 
P.M. 
Spon¬ 
taneous 
beats. 
Apex 
excitation. 
Base 
excitation. 
Demarca¬ 
tion. 
Time p.m. of 
registered 
demarcation. 
1885 
9 
Dec. 14 . 
Kitten . 
0-1 hr. SO' 
N 
s 
S 
N before 
excision 
5? 
(After 
excision) 
s 
S 
S -0344 d 
120' 
10 
Dec. 16 . 
Kitten . 
. . 
N before 
excision 
. . 
N 
N 
N 
S -0005 
?) 
? > 
?■» 
(Position 
of elec- 
S & n S 
NS 
SN 
1 
trodes 
altered) 
Later 
N 
S 
11 
Dec. 17 . 
Kitten . 
SN 
NS 
Iso¬ 
electric 
Experiment 9.—Stimulus, with heart in situ , whether at base or at apex, gave S deflection; the 
demarcation current at the time showing apex to be most injured. 
After excision the demarcation current was reversed and equal to '0344D S, and still excitation, whether 
at base or apex, gave S deflection. 
T?he first part of the experiment showed very clearly the persistence of spontaneous electromotive 
variations after the complete cessation of visible beats; the effects of excitation are paradoxical, and we 
cannot explain them. 
Experiment 10.—Kitten heart in body almost iso-electric; apex slightly negative to base. 
Heart excised. Demarcation ’0005 D S. 
Spontaneous valuation ; base and apex excitation alike gave N. 
Position of electrodes was altered from \—®—/ to 
Spontaneous beats are now S and occasionally nS. 
Base excitation gave SN. 
Apex excitation gave NS. 
Later .'—Base excitation gave S. 
Apex excitation gave N, and injury near A gave permanent deflection N, injury near B permanent 
deflection S. 
The first part of the experiment, i.e., with the electrodes in the first position, was paradoxical, but 
intelligible upon a supposition similar to that made in case of Experiment 8, viz., that the excitatory 
variation is pre-potent at the less injured part, in this case nearer to the apex. 
The effects observed in the second position of the electrodes do not contradict this supposition; they 
are obtained upon the portion of ventricle which is presumably least removed from the normal, and the 
results of excitation conform with the normal course of the excitatory variation which takes place in the 
stanniused Frog’s heart; it was the first instance which we observed of a regular diphasic variation 
indicative of the passage of the excitatory state from B to A or from A to B. The direction of the 
spontaneous variation in this case is such as to indicate that the negativity is most manifest at B, but 
that it is first manifested at A. It is probable that we have to do here with a weak first and an intensified 
second phase of a diphasic variation proceeding from A to B. 
Experiment 11.—Spontaneous variations are such as to indicate an excitatory change (negativity) 
commencing - at B and terminating at A. Excitation at A gave the reverse effect, viz., a diphasic varia¬ 
tion NS. We attempted to follow the variation by the rheotome in this case, but met with the difficulty 
that we were unable to obtain unfailing effects with short intervals between successive excitations, and 
that the prolongation of the experiment allowed of a too considerable decline of excitability for it to be 
possible to take observations with several positions of the rheotome. The necessity for allowing 
considerable intervals between test excitations was a noteworthy feature in all our experiments; the 
refractory period of excitation appears to be greatly prolonged in the excised Mammalian heart. For 
these reasons, and also because of the difficulty of knowing beforehand what intervals and what periods 
of closure to adopt for rheotome investigation, we did not pursue our experiments with this instrument. 
2 k 2 
