475 



Other sections of the heart, and experiments of other kinds, would 

 show that the cause of the rhythmic action of the ventricle, and 

 probably also of the auricles so long as they are associated with it, 

 and not with the venous trunks, is something in and near the boun- 

 dary-ring between the auricles and ventricle ; for what remains con- 

 nected with this ring, or even with a part of it in a longitudinally 

 bisected heart, retains its rhythm, and what is disconnected from it 

 loses rhythm. 



An experiment related by Heidenhain*, seems to show more pre- 

 cisely where the source of the rhythmic action of the ventricle is 

 seated. If the ventricle of a frog's heart be separated, and every 

 part of the septum of the auricles be removed from its base, so that 

 its cavity may be perfectly single ; and if, then, it be set upright on 

 a board with some blood in its cavity and around it, it will be found 

 that as pieces are cut away from its upper border, so its pulsations 

 become less and less frequent, till at length, when a zone of a certain 

 depth has been removed, they cease altogether. The depth of the 

 zone to be cut away may be nearly one-third of the length of the 

 ventricle ; and somewhere in this zone we must assume lies that on 

 which the rhythmic action of the ventricle, when alone or with part 

 of the auricles, depends. 



But wherever may be precisely the sources or centres of the 

 rhythmic action of the heart, or any of its parts (and most of these 

 details, I think, have yet to be determined, even for the hearts of 

 Amphibia, and much more for those of other orders), these experi- 

 ments seem enough to prove that the rhythm does not depend on 

 the properties of the muscular tissue alone or independently. If it 

 were so, it would be highly improbable that certain portions of the 

 heart being separated should lose rhythmic action, and others just 

 like them, so far as their muscularity is concerned, should retain it. 



This conclusion is confirmed by many experiments invented by 

 Professor Stanniusf, and often repeated by myself and others, with 

 results varying little from those which he obtained. 



Perhaps the most remarkable of them is, that if a ligature be tied 

 tightly round the place of conflux of the great veins entering the 



* Quoted in Canstatt's ' Jahresbericht ' for 1855, p. 130, from his " Disquis. de 

 nervis organisque centralibus ocrdis." Berlin, 8vo. 

 t Muller's 'Archiv,' 1852, p. 95. 



VOL. VIII. 2 N 



