268 



THE CIRCULATION OF THE BLOOD 



with the path which the impulse takes, produces a much greater differ- 

 ence of electric potential than is seen in the normal electrocardiogram. 

 When the impulse arises in the right ventricle near the base, the prin- 



Fig. 89. Paroxysmal tachycardia. Auricular origin. Note that the P deflection falls back on T. 



Rate 200 per minute. 



cipal R deflection is upwards in both leads 1 and 2. Arising near the 

 apex, the principal R deflection is up in lead 1 and down in lead 2. Two 

 extrasystoles both arising in the right ventricle are shown in Fig. 87. 



Fig. 90. Auricular fibrillation. Leads 1, 2, 3. Note the coarse fibrillation waves between the 

 R peaks, and the absence of any B deflections in relation to R. Also the unequal spacing of the R 

 deflections. 



In the case of the left ventricle, a basal ' impulse gives a downward 

 principal deflection in lead 1 and up in lead 2. When the aberrant fo- 

 cus is located near the apex of the left ventricle, the principal deflec- 



