CIRCULATION. 469 



Augmentor Centre. The situation of the centre for the augmeutor 

 nerves of the heart is not definitely known, although from analogy it seems 

 probable that it will be found in the bulb. That this centre is constantly in 

 action is indicated by the lowering of the pulse-rate after section of the vagi 

 followed by the bilateral extirpation of the inferior cervical and first thoracic 

 ganglia. The division of the spinal cord in the upper cervical region after the 

 section of the vagi has the same effect. 1 Vagus inhibition, moreover, is said 

 to be more readily produced after section of the augmentor nerves. 2 



McWilliam 3 has remarked that the latent period and the character of the 

 acceleration often accompanying the excitation of afferent nerves may differ 

 entirely from the characteristic effects of the excitation of augmentor nerves. 

 The stimulation of the latter is followed by a long latent period, after which 

 the rate of beat gradually increases to its maximum and, after excitation is 

 over, as gradually declines. The excitation of an afferent nerve, on the con- 

 trary, causes often, with almost no latent period, a remarkably sudden accel- 

 eration, that reaches at once a high value and often suddenly gives way to a 

 slow heart-beat. These facts seem to show that reflex acceleration of the heart- 

 beat is due to changes in the cardiac inhibitory centre, and not to augmentor 

 excitation. This view is strengthened by the fact that if the augmentor nerves 

 are cut, the vagi remaining intact, the stimulation of afferent fibres, for exam- 

 ple in the brachial nerves, can still cause a marked quickening of the pulse- 

 rate. In short, the action of afferent nerves upon the rate of beat is essentially 

 the same, according to this observer, whether the augmentor nerves are divided 

 or intact. 



Roy and Adami 4 believe that the stimulation of afferent nerves, such as the 

 sciatic or the splanchnic, excites both augmentor and vagus centres. The 

 augmentor centre is almost always the more strongly excited of the two, so 

 that augmentor effects alone are usually obtained. 



Action of Higher Parts of the Brain on Cardiac Centres. Repeated 

 efforts have been made to find areas in the cortex of the brain especially 

 related to the inhibition or augmentation of the heart, but with results so con- 

 tradictory as to warrant the conclusion that the influence on the heart-beat 

 of the parts of the brain lying above the cardiac centres does not differ essen- 

 tially from that of other organs peripheral to those centres. 6 



Voluntary control of the heart, by which is meant the power to alter the 

 rate of beat by the exercise of the will, is impossible except as a rare indi- 

 vidual peculiarity, commonly accompanied by an unusual control over muscles, 

 such as the platysma, not usually subject to the will. Cases are described by 

 Tarchanoff 6 and Pease, 7 in which acceleration of the beat up to twenty-seven 



1 Tschirjew, 1877, p. 164 ; Strieker and Wagner. 1878, p. 370. 



Sustschinsky, 1868, p. 164. 3 McWilliam, 1893, p. 472. 



4 Roy and Adami, 1892, p. 260. 



5 See Danilewsky, 1875, p. 130; Bochefontaine, 1876, p. 140; 1883, p. 33; Balogh, 76; 

 Eckhard, 1878, p. 185; Bechterew and Mislawsky, 1886, pp. 193, 416; Franck, 1887, p. 162. 



6 Tarchanoff, 1884, p. 113. 



7 Pease, 1889, p. 525. 



