CARDIAC REFLEXES. 57 



fully determined. The heart itself possesses afferent nerves, and by 

 means of these it is quite conceivable that it can renexly control its own 

 beat. The afferent nerves of the heart do not include nerves which 

 excite sensations of touch or pain, at any rate when the organ is in a 

 normal condition. On touching the heart of Viscount Montgomery, who 

 had, through an accident, lost part of the thoracic wall, Harvey was 

 unable to excite any signs of consciousness. General retiex movements 

 can, however, be excited. 1 Thus Francois-Franck succeeded in producing 

 reflex inhibition of the respiration by chemical stimulation of the inner 

 wall of the heart. 2 



By excitation of the central ends of the different nerves which are 

 found running superficially on the anterior wall of the ventricle, Wool- 

 dridge obtained the following results : 3 — 



1. Slowing of the pulse rate and a rise of arterial pressure. 



2. Slowing of the pulse rate, followed by acceleration and a fall of 

 arterial pressure. 



On stimulation of the nerves which course over the posterior wall 

 of the ventricle, he observed — 



1. Acceleration of the pulse rate. 



2. Slowing of the pulse rate and a fall of arterial pressure. 



3. A rise of arterial pressure. 



4. A fall of arterial pressure. 



While stimulation of the central end of one vagus nerve — if the other 

 end be intact — slows the heart, the arterial pressure may rise or fall, 

 according as depressor or pressor fibres are in the ascendancy. The 

 result varies in different individuals. From the right or left vagi, 

 opposite effects on the arterial pressure may be obtained. The afferent 

 nerves examined by Wooldridge run in the vagi. The arterial pressure 

 may reflexly excite the cardiac centres in the bull) by way of these 

 afferent fibres. In the case of the depressor nerve we have an analogous 

 example. 



After carrying out a division of the spinal cord in the cervical region, 

 a sudden injection of blood at a high pressure into the peripheral end of 

 the carotid artery provokes slowing of the heart. 4 Sudden anaemia of the 

 bulbar centres has the same effect, whether it be produced by ligation of 

 the cerebral arteries or by compression of the brain. The vagus centre 

 is first excited and then paralysed. Since acute anaemia of the spinal bulb 

 primarily causes a slow beat and a rise of arterial tension, it is curious 

 that the vagus centre should be directly excited to greater activity by a 

 rise of arterial tension, which increases the supply of blood to the spinal 

 bulb. It is conceivable in the above experiment that the sudden expan- 

 sion of the cerebral arteries by a high-pressure injection momentarily 

 pinches the spinal bulb within the closed cranial cavity, and renders it 

 anaemic. 5 If this suggestion be accepted, and it be agreed that the vagus 

 centre is in all cases directly excited by anaemia, how is the normal 

 interdependence of the arterial tension and cardiac inhibition to be 

 explained ? This is a cpiiestion which cannot be settled, since the afferent 

 nerve of the heart is also the afferent nerve or channel of inhibition. 



1 Goltz, Virchow's Archiv, 1863, Bd. xxvi. S. 5. 



2 "Trav. du labor, de Marey," 1880, tome iv. p. 382. 



3 Arch. f. Physiol., Leipzig, 1883, S. 539. 



4 Francois-Franck, "Trav. du labor, de Marey," 1877, tome iii. p. 276. 



5 Hill,' "The Physiology and Pathology of the Cerebral Circulation," London, 1896, 

 p. 135. 



