( 79 ) 



Cerlain period of normal contractions. In the transition of the normal 

 period into the period of slow contractions, regularly curves are 

 recorded, which together with curves formerly published of the living 

 frog-heart (loc. cit.) throw light, on one of the, at least four 

 varieties of P. A. which in my opinion must be distinguished, at 

 least in the physio-pathology of the frog-heart. As to the three 

 other types of P. A. I think, that the way may become clear to 

 explain them equally. 



First form of P. A. with equal intervals. 



The ventricle beats in regular rhythmus alternatingly stronger and 

 weaker, the beginning of the weak contraction is separated by the 

 same length of time from the preceding and following contraction 

 (fig. 1). This variety was described by Engelmann ') and ascribed to 

 momentaneouslv diminished conductivity. V. I!. Hofmaxn') has shown, 

 that this form of P. A. is often dependent on slight changes of the 

 frequency of the heart-beat, Straob proved, that this P. A. under 

 influence of antiarine easily gives way to "Puls-halbirung", which I 

 often saw under influence of digitalis dyalisata. 



Second form of P. A. with retarded smul I contraction. 



In a former publication') I described an example of P. A. observed 

 in the dying frog-heart, where the interval between the greater and 

 smaller V s was longer than between the smaller and larger con- 

 traction. There it appeared, that the auricle continued to beat regu- 

 larly. By comparing the intervals A — V, preceding the greater and 

 smaller contractions, we concluded then, that the con traction wave in 

 the A — F bundle, eventually in the ventricle itself, might be slowed, 

 which was the cause that the V, not only came too late, bul was 

 also weaker. 



The supposition, that this V. A. in cerlain cases might depend on 

 changes of conductivity within the ventricle, had right of discussion, 

 although this could not be strictly proved, as is remarked by 

 Wenckebach. For one can never with certainty conclude to a change 

 of conductivity within a heart cavity (e. g. within V) if the interval 

 between the contractions of two cavities (e.g.' A — V) remained equal. 

 But with the same certainty this meritorious observe)- is mistaken, 

 when he, from the few curves (10a and \0b) of Engelmann generalises 

 to the contrary i. e. to the exclusion of a similar relation in other 



') Emgelmann, Arch. f. d. ges. Physiologie. Bd. 02. 1896. p. 556 seq. 



2 ) Hofmann. Arch. f. d. ges. Physiologie. Bd. 84. 1900. p. 165. 



s ) L. J. J. Muskens, Nederl. Tijdschr. v. Geneeskunde. 1902. No. II. Biz. 591. 



