1 92 THE CONTRACTION OF CARDIAC MUSCLE. 



another phenomenon, observed originally by Bowditch, 1 namely, the pheno- 

 menon of the " Treppe," or staircase phenomenon, which consists in the 

 fact that, when a series of single induction shocks of the same strength 

 are sent in to the muscular tissue of the quiescent frog's ventricle or 

 apex, the contractions are not all of the same size, but the first is the 

 smallest, and they then gradually increase up to a maximum. From this 

 experiment it is concluded that every stimulus which causes a contraction 

 produces in addition a beneficial change in the muscular tissue, so that it 

 is more excitable and able to contract more strongly than before the con- 

 traction. How such beneficial effect is brought about, whether, as Hering 

 would say, by the assimilation process which is produced by the dissimi- 

 lation stimulus being greater than is necessary to produce autonomous 

 equilibrium, or in some other way, such, for instance, as by means of 

 nerve fibres, which are excited simultaneously with the muscular tissue, 

 cannot be determined at present. The question will, however, be con- 

 sidered again in connection with the action of the intracardiac nerves. 



On Fibrillar Contractions. 



Another question which arises in connection with the conductivity 

 of cardiac muscle, is the question of the co-ordination of the different parts 

 of the ventricle or auricle. Why is it that the contraction of the 

 ventricle takes place as a whole, and not as a series of separate contrac- 

 tions ? In the case of warm-blooded animals, a marked inco-ordination of 

 the different parts of the muscular tissue of the ventricle, known by the 

 name of fibrillar contractions, can be brought about by the application of 

 a strong tetanic current to the surface of the ventricle, or by the ligature 

 of one or more coronary arteries. How are these fibrillar contractions 

 to be explained ? 



According to the observations of Kronecker and Schmey, 2 a puncture 

 in a particular spot on the septum between the ventricles always brings 

 about this kind of inco-ordination, and they conclude, therefore, that 

 the ventricle possesses here a co-ordination centre which harmonises 

 the contractions of all the ventricular muscle fibres, and so causes a 

 single contraction of the whole ventricle at each heart-beat, instead 

 of the disorderly disjointed contractions of separate muscle-strands, 

 such as are seen in the condition of fibrillar contraction. Against 

 this view it has been pointed out by MacWilliam, 3 that nothing of 

 the nature of any nerve centre is to be found at the place indicated ; 

 that after the destruction of this supposed centre the ventricle will 

 frequently recover from these inco-ordinated movements, and beat again 

 regularly and well, and that the same fibrillar contractions can be 

 induced in the regularly beating isolated apex of the heart — in tissue, 

 therefore, entirely removed from this supposed co-ordination centre. 



With respect to the fibrillar contractions produced by strong tetanic 

 stimulation, they are, it Avould appear, confined to the hearts of warm-blooded 

 animals. In these animals there, is a distinct difference between auricle and 

 ventricle in this respect — when the ventricle muscle is thrown into this 

 condition of inco-ordinated fibrillar contraction, it is said not to recover either 

 by nerve stimulation or other means ; when, however, similar movements are 



1 Op. cit. " Sitzungsb. d. k. Akad. d. JVissensch. zu Berlin, 1884, S. 87. 



' J Journ. Physiol., Cambridge and London, 1887, vol. viii. p. 296. 



