412 



Messrs. Sanderson and Page 



[May 23, 



trically), by creosote, or by a fine wire covered with a thin layer of 

 fused nitrate of silver. 



6. Comparison of Sound with Uninjured Spots on the Surface of the 

 Besting Heart. — When the resting heart is connected by its base and 

 apex with a galvanoscopic circuit, and one of the two isoelectrical 

 spots on the surface of the organ by which it is led off is injured in 

 any of the ways above mentioned, the injured spot is found to have 

 become negative to the sound surface. The electrical difference between 

 them may amount to 0*03 volt, but, as Engelmann found, that 

 difference usually diminishes very rapidly. 



This effect is for the most part not dependent on the distance of the 

 sound spot from the injured spot. Thus, if an injured spot near the 

 apex is compared (a) with a sound spot 2 millims. from it, and 

 (b) with another near the base, i.e., about 5 millims. distant, it is 

 often found that the differences between the two results are very in- 

 considerable. This experiment shows that the electromotive forces 

 developed by injury have their seat in the immediate neighbourhood 

 of the injured surfaces. 



7. Influence of Radiant Heat. — When two isoelectrical points, {e.g., 

 at apex and base) on the surface of the heart are led off, and one of 

 them is warmed by the approach of a platinum coil (about 2 millims. 

 in diameter) heated by a voltaic current and brought into its neigh- 

 bourhood (3 millims. distant) for a period of one second, the warmed 

 spot becomes positive to the other. The amount of difference has not 

 been observed to exceed one-thousandth of a Daniell. No movement 

 of the needle occurs until about a second after the approach of the 

 coil. This effect is transitory, its duration being less than five seconds. 

 If the distance at which the coil is placed is diminished, the warmed 

 surface becomes for a moment positive, then permanently negative. 

 A similar effect is observed when the warming is prolonged without 

 diminishing the distance. 



Section III. — Characters and Modifications of the Electrical Variation. 



•As was first observed by Kolliker and H. Muller in 1854, an elec- 

 trical disturbance or variation precedes and accompanies each con- 

 traction of the ventricle of the heart of the frog. In the uninjured 

 heart the extent of this variation is extremely small, but is at once 

 increased by injury. 



8. The Normal Variation. — In the uninjured pulsating heart the 

 variation consists of two phases, viz., of an initial disturbance of 

 short duration, in which the apex becomes positive, and of a much 

 longer second phase, in which the apex tends to negativity. This 

 statement, which relates to the heart cut off through the sinus, is also 

 applicable to the organ while it still forms part of the body. In the 

 entire heart the initial phase begins a quarter of a second before the 



