ix CAEDIAC MUSCLE AND NERVES 337 



centres are in continuous slight excitation, on which depends the 

 tone of the vagi, exhibited in the acceleration of the beats, on 

 simple division of that nerve, or administration of atropin. This 

 effect does not appear when section of the vagus is preceded by 

 division of the cervical cord (Bernstein). Acceleration is also 

 obtained after dividing the splanchnic nerve (Asp), due not 

 to the lowering of blood pressure, which usually produces the 

 opposite effect, but to the depression of vagal ton us. In the 

 newborn, touicity seems to be wanting in the vagus till after the 

 second week, since in kittens neither section of the vagus nor 

 exhibition of atropiue causes acceleration of pulse (Soltniann). 



It is possible that the systolic nerves and centres also have 

 normally a certain tonicity, although subordinate to the diastolic 

 nerves. After extirpation of the lower cervical and stellate 

 ganglia on both sides, there is, when the vagi are divided, a 

 marked acceleration of rhythm (Tschirjew, Strieker, and Wagner). 

 With intact vagi, a permanent slowing of beat can be obtained 

 on dividing the accelerators (Timofeew). 



The tone of the cardiac centres and nerves may be automatic or 

 reflex, or as is most probable, automatic and reflex in character. It 

 is known that the frequency of cardiac rhythm normally stands 

 in inverse ratio to the height of the average arterial blood pressure, 

 i.e. that rise of blood pressure produces lowering of pulse frequency 

 and vice versa. After section of the vagi this ratio is no longer 

 so distinct and constant, showing that the blood-pressure regulates 

 the tone of the cardiac nerve centres, those of the vagus in 

 particular, directly or reflexly. 



BIBLIOGRAPHY 



Iii addition to previous Bibliographies, see also : 



Fundamental Memoirs in re Physiology of Cardiac Muscle and Intracardiac 

 Nervous System : 



STANNIUS. Arch. f. Anat. u. Physiol. , 1852. 



ECKHARD. Beitriige /ur Anat. und Physiol. Giessen, 1858-60. Experimentelle 



Physiol. des Nervensystems. Giessen, 1866. 

 GOLTZ. Arch, fiir path. Anat., 1860-62. 

 BOWDITCH. Ber. d. sachs. Ges. d. Wiss., 1871. 

 LUCIANI. Ber. d. sachs. Ges. d. Wiss., 1873. Edizione italiana, Rivista clinic.i 



di Bologna, 1873. 



KRONECKEU und STIRLING. Beitriige zur Auat. und Physiol., 1874. 

 MAREY. Compt. rend., 1879. 



GASKELL. Arch, de physiol. normale et pathologique par Brown-Sequard, 1888. 

 FANO. Lo Sperimentale, 1885. Archivio per le scienze mediche, 1890. Archives 



ital. de biologie, 1888. 



ENGELMANN. Arch, nuerlaiidaises, 1893-97. Arch. f. Anat. u. Physiol., 1902. 

 KRONECKER. Zeitschrit't fiir Biologie, 1897. 



BOTTAZZI. Pubblicazioni del R. Istituto di Studi superiori di Firenze, 1897. 

 H. E. HERING. Pfliigers Arch. Ixxxvi., 1901 : cxv., 1906; cxvi., 1907. 

 A. J. CARLSON*. American Journal of Physiology, xii., 1905. 

 F. B. HOFMANN-. Nagel's Handbuch der 'Physiol. L, 1905. 

 M. HUMBLET. Arch, intern, de Physiol., 1904, i. 

 E. VON CYON. Die Nerven des Herzens. Berlin, 1907. 



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