654 



PRINCIPLES OF GENERAL PHYSIOLOGY 



wave, which seems improbable. On the other hand, the fact that, as shown 

 in curve C, this fourth phase, as well as the third, is absent when the wave 

 disappears before it reaches the second electrode, indicates that it is due to 

 a disturbance, excitatory or inhibitory, which travels along the ureter. If 

 it were an inhibition controlled by nerve centres, as in the intestine, it might 

 perhaps have a different time course from the wave of contraction, but it would 

 seem useless for it to follow the contraction wave at the further electrode. 

 The inhibition wave sometimes occurs independently of the excitation, so that 

 a series of monophasic responses in the positive direction may be seen, only 

 occasionally followed by a negative one. The monophasic nature is due to 

 the disappearance of the wave in a region of decrement before it reaches the 

 second electrode. 



In the spontaneous peristaltic waves in the crop of Aplysia, it was shown 

 by Dittler (1911) that each wave consists of a simple negative change, without 

 the electropositive accompaniment of that of the ureter. This wave is very 



FIG. 210. TYPICAL FORM OF THK HUMAN ELECTRO-CARDIOGRAM, AS OBTAINED 

 BY LEADING OFF FROM RIGHT ARM AND LEFT ARM (LEAD 2). 



C, Carotid pulse. 



E, Electro-cardiogram, with the designation of the component parts or waves as given by 

 Einthoven. 



Scale divisions of abscissa), 0*01 sec. 



Scale divisions of ordinates, 10 - * volts. 



Einthoven regards P as the only component belonging to the auricle, Q, Ji, S, T all being 

 parts of the ventricular complex (see text, page 655). 



(Einthoven, 1913, p. 68.) 



slow, the total duration being about fourteen seconds, but it gives no indication 

 of being anything but a single contraction, not a short tetanus. So far as could 

 be made out, the duration of the mechanical response appeared to coincide with 

 that of the electrical one ; so that, if the latter is an expression of the excitatory 

 state, and not of the state of contraction, the excitatory state in this case, at all 

 events, must not merely precede that of contraction but last as long as the latter 

 does. 



The Heart. Apart from the interest of the phenomenon itself, the electrical 

 change in the heart has become of great importance, not only as a means of 

 following the course of the contraction, but as a clinical method of investigating 

 irregularities in the heart beat (see the book by Lewis, 1913). 



v An exact analysis of the electrical change was first made by Burdon-Sanderson 

 and Page (1880), who showed that, in the frog's ventricle, a diphasic deflection 

 occurred, similar to that which we have described in nerve and muscle. This was 

 of such a direction as to show that the excitation process started at the base, and 

 progressed as a wave to the apex. Fig. 208 is a photograph by Gotch (1910) of 

 the phenomenon in the tortoise. In this case one electrode was on the auricle, 

 the other on the apex of the ventricle, so that the auricular change is also shown, 

 and is seen to be similar to that of the ventricle, but smaller. I made, in conjunc- 

 tion with Starling (1892, 1), Observations on the corresponding change in the 



