462 On the Action of the Excised Mammalian Heart, [Dec. 16, 



8. In an excited beat, in ventricle or auricle, of an excised heart, 

 all parts are not in action simultaneously. 



9. An excited contraction starts from the point excited— from the 

 base if the base is stimulated — from the apex if the apex is stimu- 

 lated. 



10. The excited contraction travels from its point of origin, indif- 

 ferently in any direction in the substance of the ventricle. 



11. The rate of the wave of contraction measured by the graphic 

 method varies, according to the temperature and state of the heart, 

 from 3 to 85 cm. per second. 



12. The velocity is (cmteris 'paribus) greater in the hearts of large 

 than in the hearts of small animals. 



13. In spontaneous contractions of the ventricle the movement of 

 the apex appears to precede that of the base. 



Note. — We have followed the wave of both spontaneous and excited 

 contraction of the frog's ventricle by the graphic method, and 

 measured its rate. The rate is from 40 to 80 mm. per second. In 

 spontaneous contraction, the movement of the base precedes that of 

 the apex. 



14. All parts of the uninjured heart are iso-electric ; the apex, 

 however, is often slightly negative to the base. 



15. The electrical variation of spontaneous contraction is sometimes 

 diphasic, (corresponding to the double variation of the beat of the 

 frog's heart), sometimes monophasic. 



16. Electrical variations can be detected after visible contractions 

 have ceased. 



17. The direction of the electrical current follows no definite rule 

 in our observations, negativity of apex preceding sometimes negativity 

 of base, at other times the reverse taking place. 



18. The diphasic variation of excited contractions indicates that 

 the part stimulated is first negative then positive to other parts. 



19. Under conditions of lowered excitability a weak excitation will 

 give a monophasic, a strong excitation a diphasic variation. 



20. Towards the close of the period of excitability, the variation of 

 the excited beat is single. It is less frequently single at the outset of 

 experiment. 



21. When excitatory variations can no longer be obtained, injury 

 will produce a change of electrical state indicating negativity of the 

 part injured. 



