GANGLIONIC APPARATUS IN HEART. 309 



certain tension exists within it even during diastole. The 

 amount of this is shown by the height of the diastolic curve 

 above the zero-line. When tlie vagus is irritated, the tension 

 during the diastole sinks ; but, if its inhibitory fibres be para- 

 lysed by atropia, which leaves its quickening ones unhurt, irri- 

 tation has then the opposite effect, and the tension during the 

 diastole becomes greater and greater till the heart may stand 

 still in firm contractions. 



What Fart of the Ganglionic Aj^imratus in the Heart is 

 affected? — In dealing with this part of the subject, we tread on 

 very unstable ground, for here pharmacology has almost run 

 ahead of physiology ; and even with our physiological know- 

 ledge of the nervous structures of the heart a great deal of 

 speculation is mixed. We know tliat the heart contains ganglia 

 scattered through its substance, but found in the greatest num.- 

 bers in the septum between the auricles and in the auriculo- 

 ventricular groove of the frog's heart, in wliich they have 

 been chiefly investigated. As the heart, long after it has been 

 separated from the body, or the apex after it has been cut off 

 from the ventricle, will still continue to beat rhythmically, the 

 cause of the contractions must be contained in itself ; and we 

 assume the cause in each part to be the cardiac ganglia, and 

 suppose that they are connected by some apparatus which keeps 

 them working harmoniously together, as the different parts of 

 the heart all contract in a definite order so long as it is unin- 

 jured. Their action may be rendered slow or quick by nerves 

 passing to them from Without, both the retarding and the 

 quickening nerves being contained in the vagus in the frog 

 while in manmials the retarding ones are found in the vagus, 

 and the quickening ones chiefly in the third branch of the 

 ganglion stellatum (or first dorsal generally joined to the last 

 cervical), although some may also be found in the vagus. 



Some physiologists consider that the function of all the 

 ganglia is simply to keep up rhythmical movements in the 

 heart. Others hold that only some of them, found chiefly 

 in the venous sinus and ventricle, have this function : 

 while others are inhibitory, and restrain the action of the 

 former. These inhibitory ones exist cliiefly in the seilum 



