CARDIAC GANGLIA AND CARDIAC MUSCLE. 315 



administration to mammals in which the spinal cord, vagi, 

 sympathetics and depressors have all been divided, or when it 

 is applied to the excised heart of a frog. 



Is Quiche7iing of the Excised Heart dve to Parah/sis of Inhibi- 

 tory or Stimulation of Accelerating Ganglia? — It is possible that 

 the quickening may be due to paralysis of the inhibitory 

 ganglia in the heart, and not to stimulation of the quickening 

 ganglia. This can be decided by paralysing the inhibitory 

 ganglia by means of atropia, before applying the poison to be 

 tested — e.g., veratria. If the latter poison exercise a stimulating 

 action on the quickening ganglia, it will quicken the heart after 

 atropia has been applied. If it simply paralyse the inhibitory 

 ganglia, it will have no further effect after their power has been 

 destroyed by atropia. In the diagram, I have figured inter- 

 mediate structures c and D between the quickening nerves and 

 ganglia, so as to correspond with those of the inhibitory appa- 

 ratus ; but whether they really exist or not, we cannot at 

 present say. 



Is the Co-ordinating Apparatus of the Cardiac Ganglia Para- 

 lysed'? — Eegarding this apparatus we know almost nothing. 

 When the heart is dying its rhythm is often disturbed, and two 

 or three contractions of the auricles may occur for every con- 

 traction of the ventricle. When laudanum is poured into the 

 heart, the rhythm is quite reversed ; for after each pause the 

 ventricle contracts first, and contraction of the auricle follows 

 it. Digitalis and some other poisons cause peristaltic move- 

 ments in the ventricle ; and occasionally some spots in the 

 ventricle continue to pulsate while the rest of it remains lirmly 

 contracted and motionless. These effects are probably due 

 to disturbance of the apparatus which connects the different 

 motor ganglia in the heart and causes them to work in unison. 



Are the Muscular Fihres of the Heart Paralysed ? — We test 

 this by applying an irritant to them directly, and seeing whether 

 or not they contract. If the motor ganglia be uninjured, the 

 application of an irritant generally produces a rhythmic contrac- 

 tion of the whole heart ; but, if they be paralysed while the 

 muscular fibre is healthy, the irritation only causes a local con- 

 traction of the part to which it is applied. 



