ELECTRO-CA RDIOGRA M 



35 



potential at this time between its various parts. The T-wave he 

 considers to be produced, when it is present, merely because the 

 . excitated state does not dis- 

 appear simultaneously over 

 the whole ventricle. 



In the ventricle of the 

 frog and tortoise the same 

 order of development of the 

 negative change is seen, the 

 base first becoming rela- 

 tively negative, then the 

 apex, and then the neigh- 

 bourhood of the origin of 

 the aorta (Fig. 307). 



Fig. 308. Electro-Cardiograms from Man 



(Capillary Electrometer) (Einthoven and Under certain conditions 

 Lint). Obtained from the same individual the action current of the heart 

 at rest (upper curve), and immediately after may stimulate the phrenic 

 vigorous muscular exercise (lower curve), nerves, causing the dia- 

 The elevations A, C, D, indicate negativity phragm to contract synchro- 

 of base to apex; the notches B and C lf nega- nously with the heart, 

 tivity of apex to base. The Human Electro- Cardi- 



ogram. An electrical change 



accompanies each beat of the human heart. Waller first showed how 

 this may be demonstrated by means of the capillary electrometer. 



Einthoven and 

 Lint then investi- 

 gated the pheno- 

 menon on a large 

 numberof persons. 

 From the photo- 

 graphic records of 

 the movements of 

 the meniscus they 

 constructed the A h 



true electro - car- 

 diographic curves* 

 (Fig. 309;, which 

 express the actual 

 changes in the po- 

 tential difference 

 between the two 

 points led off. 

 They distinguished 

 in every one of 

 these constructed 

 electro-cardio- 

 grams five points 

 or cusps, three of 

 which indicate re- 

 lative negativity 



Fig. 309. Constructed Elec- 

 tro-Cardiograms from Man 

 (EinthovenandLint). Time 

 is laid off along the hori- 

 zontal, and electromotive 

 force along the vertical axis, 

 the same space being allot- 

 ted to ten millivolts (i.e., 

 Y^J volt) as to one second. 



Fig. 310. Illustrating the 

 Position of Favourable and 

 Unfavourable Leads for 

 the Human Electro- 

 Cardiogram (Waller). 



* In all accurate work with the capillary electrometer such curves must be 

 obtained by construction from the direct photographic records, which do not 

 themselves give a.n absolutely true picture of the variations. 



