1883.] On the Innervation of the Mammalian Heart. 227 



In the frog, stimulation of the sinus produces stillstand of the heart. 

 The inhibitory fibres have at any rate here a provisional ending. 



On the other hand the result of stimulation of the ventricle may be 

 regarded as a form of acceleration. 



In the dog, the vagus and accelerans nerves act on different 

 mechanisms (Baxt). 



Having regard to these facts the possibility of the ventricle nerves 

 being accelerator presented itself. 



To know the function of these nerves was not only interesting, 

 per se, but also as forming an appropriate introduction to the nearer 

 investigation of the nervous mechanism of the mammalian heart. 



The following observations on the accelerans will be first re- 

 corded : — 



Hitherto in the dog, the experiments on the accelerans nerve have 

 been carried out almost exclusively with that of the right side. It 

 was more convenient in the present case to work with the left nerve 

 (Ansa Vieusseni). The author has observed that in many cases 

 stimulation of the left accelerans is without any influence on the 

 rhythm of the heart ; and that this was not due to accident, such as 

 lowering of the temperature, was shown by the control stimulation of 

 the right accelerans. This fact is not without importance for the 

 remainder of the research, as will be seen. 



Minimal electrical stimulation of the vagus overcomes completely 

 the action of the accelerans, but the accelerans overcomes the normal 

 slight tonic action of the vagus (Baxt). In an experiment of the 

 author there existed, owing to stimulation of the medulla, a most 

 powerful tonic vagus action. Thus — 



Average of pulse beats before division of vagi. ... 8 

 „ „ after „ „ ... 18 



Yet stimulation of the accelerans overcame this and produced 

 marked quickening. If during the stimulation of the accelerans a 

 very small cardiac branch of vagus (in the thorax) were stimulated, 

 it exerted its inhibitory influence, and overcame the accelerans, 

 though it did not depress the pulse to the same degree that the tonic 

 vagus action did. With our present knowledge, this experiment 

 points to a difference between the stimulation of a nerve from its 

 centre, and the electrical stimulation of its trunk. 



The ventricular nerves are very numerous, but require in the dog the 

 use of special methods, in order to be seen well ; the author recom- 

 mends strong carbolic acid for this purpose. These nerves form at any 

 rate the greater part of the nervous connexion between the auricle 

 and ventricle. They cannot be adequately stimulated after they have 

 passed on to the ventricle, since the stimulus affects the heart itself 

 too. This is more particularly the case for electrical stimulation. As 



Q - 



