ITS AJS AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



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

 or intact. 



Roy and Adami 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. 



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

 in the minute was produced, together with increase of blood-pressure, from 

 vaso-constrictor action. The experiments are dangerous. 1 



Peripheral Reflex Centres. — It is now much discussed whether the periph- 

 eral ganglia can act as centres of reflex action. According to Franck 2 the excita- 

 tion of the central stump of the divided left anterior limb of the annulus of 

 Vieussens is transformed within the first thoracic ganglion, isolated from the 

 spinal cord by section of its rami communicantes, into a motor impulse trans- 

 mitted by the posterior limb of the annulus. This motor impulse causes, inde- 

 pendently of the bulbo-spinal centres, a reflex augmentation in the action of the 

 heart, and a reflex constriction of the vessels in the external ear, the submaxil- 

 lary gland, and the nasal mucous membrane. This experiment, in conjunction 

 with the tacts in favor of other sympathetic ganglia acting as reflex centres/ 

 seems to demonstrate that some afferent impulses are transformed in the sym- 

 pathetic cardiac ganglia into efferent impulses modifying the action of the 

 heart. It' this conclusion is confirmed by future investigations it will pro- 

 foundly modify the views now entertained regarding the innervation of the 

 heart. 



The exp&irnenU of Stannius, published in 1852, have been the starting- 

 point of a very -rent number of researches on the innervation of the frog's 

 heart. Stannius observed, among other facts, that the heart remained for a 

 time arrested in diastole when a ligature was tied about the heart precisely at 

 the junction of the sinus venosus with the right auricle. No sufficient 

 explanation of this result has yet been given, nor is one likely to be found 

 until the innervation of the heart is better understood. Stannius further 



1 Van de Velde : Archivfur die gesammte Physiologic, 1897, lxvi. p. 232. 



2 Franck : Archives de Physiologic, 1894, p. 721. 



3 Langley and Anderson : Journal of Physiology, 1894, xvi. p. 435. The attempt of Prof. 

 Kxonecker to demonstrate a co-ordinating centre in the ventricles may be mentioned here (Zeit- 

 schrift fur Biolagie, 1896, xxxiv. p 529). 



