385 



Idio- Ventricular Periodicity. 

 By D. H. DE SouzA and J. A. Hewitt. 



(Communicated by Prof. W. D. Halliburton, F.R.S. Received September 30, 



1921.) 



(From the Physiology Department, University of London, King's College.) 



When the excised heart of the frog is perfused under certain conditions, 

 the beats lose their normal regularity, and occur in periodic groups with 

 a long pause between every two groups. This phenomenon was first 

 investigated systematically by Luciani* in 1872, and, in consequence, the 

 groups are often referred to as " Luciani groups." They are not infrequently 

 seen in experiments in which a Synies cannula, inserted into the heart 

 through the inferior vena cava or sinus venosus, is kept in place by a 

 ligature tied between the sinus venosus and the auricles, in the position of 

 the first Stannius ligature. When the ligature is tied, the auricles and 

 ventricles cease to beat, but if the heart is excised and then perfused 

 through the cannula by Symes's method,f the whole heart usually beats 

 again, and the beats may show periodic grouping before settling down to 

 •ci normal regularity. Sometimes, too, groups occur in hearts in which the 

 perfusio'h. by Symes's method has been going on for some time and the 

 heart has been beating regularly. 



The conditions of occurrence of the groups have been studied by several 

 physiologists, and the general opinion seems to be, like that of Gaskell,J 

 that they are due to an asphyxial state of the heart, that the pauses indicate 

 a complete heart block, and that the groups of beats occur when the block 

 has become only partial, so that some beats are able to get through from 

 sinus venosus to auricles and ventricles. 



In the course of some perfusion experiments which we have been carrying 

 ■out, we obtained a tracing which, it seems to us, cannot be explained in 

 this way. As it illustrates a phenomenon in connection with periodic 

 grouping of which we can find no description, we put it on record in 

 this note. 



Experiment. — A cannula was inserted into the heart of a pithed female 

 frog through the inferior vena cava, and the heart was secured to the 

 cannula by a ligature passing round it in the groove between the sinus 

 venosus and the auricles, and not including the aortic trunk. The heart, 



* Luciani, ' Human Physiology ' (translated by F. A. Welby), vol. 1, p. 302 (1911). 



+ Symes, 'Proc. Physiol. Soc, Jour. Physiol.,' vol, 43, p. xxv (1912). 



+ Gaskell, ' Text-book of Physiology ' (edited by E. A. Schafer), vol. 2, p. 226 (1900). 



