380 The American Naturalist. [April, 
temperature and an accumulation of waste products, the perspiratory 
activity is useful as a regulator by cooling the body and eliminating 
the wastes. 
Electrical Phenomena in Beating Heart.—Dr. Waller has 
investigated 2 more fully the electromotive changes in the contracting 
mammalian heart. The exposed and spontaneously beating heart of 
the cat was studied zm sifu by means of the capillary electronometer. 
The electrical variation of the ventricle resulting from a single beat 
was found to be diphasic, indicating negativity of apex followed by 
negativity of base. This confirms the author’s former discovery by 
mechanical methods that the contraction of the apex precedes that of 
the base, which is the reverse of what takes place in the frog. Some 
preliminary experiments were tried on animals to determine whether 
-the electrical variations accompanying the heart beat could be detected 
on the surface of the body. These were successful, and led to a study 
of the electrical variations of the heart in man. 
It was found that leading off from points of the surface of the body 
remote from the heart in the intact animal or in man gave the same 
diphasic variation accompanying the ventricular contraction, the au- 
ricular contraction giving no electrical indication. ‘The most favor- 
able positions for the electrodes are on either side of a line running at 
right angles to the long axis of the heart. Such a “line of zero 
potential’’ in the normal human being, with heart tilted to the left, 
extends from the left shoulder to the right side ; in the quadruped, with 
heart toward neither side, it is transverse to the body axis. Leading 
off from any point anterior to this line is equivalent to leading off 
from the base of the ventricles; leading off from a point posterior to 
this line is equivalent to leading off from the apex. Thus, in man 
electrodes placed on the right hand, and either the right or the left 
foot or left hand, gave a good variation; not so the left hand, and 
either the right or left foot. Favorable combinations are the mouth 
and the left hand, the right foot, or the left foot ; an unfavorable one, 
the mouth and the right hand. In the cat a favorable combination is 
either anterior extremity with either posterior extremity, but not the 
two anterior extremities with each other. The electrical variation 
precedes the mechanical movement of the heart, and is always diphasic, 
indicating, as in the exposed heart, negativity of apex followed by 
negativity of base. It would seem, then, that in the human heart, 
and mammalian hearts generally, unlike the amphibian, the contrac- 
2 Philosophical Transactions, Vol. 180 (1889), B., p. 169. Cf. also Vol. 178 (1887), 
B., p. atk. 
