314 OF THE CIRCULATION OF THE BLOOD. 



(depressor nerve) ; 2. The central end of the vagus of the opposite side ; 3. 

 Almost any sensory nerve in the case of warm-blooded animals, the fifth, 

 according to Heriug and Kratschmer, having a very special action ; 4. The 

 abdominal viscera in the frog; 5. The splanchnic and cervical sympathetic. 

 In these instances the cardio-inhibitory nerves appear to be excited in a 

 reflex manner. The inhibitory action of the right Vagus upon the heart is 

 much more marked than the left in the tortoise. 1 It may just be noticed 

 that both Dr. Rutherford and Dr. Coates, 2 of Glasgow, have shown that 

 irritation of the vagus always diminishes the absolute amount of work done 

 by the heart. 



There is reason to believe that the depressing effects of shock may be ex- 

 erted both through the vagus and through the sympathetic system of nerves, 

 and that considerable disturbance may ensue from lesions of such branches 

 of these nerves as are most nearly connected with the heart. For the well- 

 known fact of sudden death not unfrequently resulting from a blow on the 

 epigastric region, especially after a full meal, without any perceptible lesion 

 of the viscera, seems to indicate that a violeut impression upon the widely- 

 spread coeliac plexus of Sympathetic nerves (which will be much more ex- 

 tensively communicated to them when the stomach is full, than when it is 

 empty), may cause the immediate cessation of the heart's action probably 

 by a reflex action exerted on the pueumogastrics, in the same manner as a 

 severe injury of the braiu or spinal cord. And a case has been put on 

 record, in which the heart's pulsations were occasionally checked for au in- 

 terval of from 4 to 6 beats, its cessation of action giving rise to the most 

 fearful sensations of anxiety, and to acute pain passing up to the head from 

 both sides of the chest these symptoms being connected, as appeared on a 

 post-mortem examination, with the pressure of an enlarged bronchial gland 

 upon the great cardiac nerve. 3 Czermak 4 has produced all the usual effects 

 of irritation of the vagus in his owii' person by carefully applied pressure 

 over the vagus in the neck. 



245. Nerves Accelerating the Action of the Heart. The action of the heart 

 cannot only be rendered slower or stopped by irritation of certain fibres run- 

 ning in the vagus, but by the irritation of other nerves its movements can 

 be accelerated. V. JBezold observed that irritation of the cervical sympa- 

 thetic is followed by increased frequency of the heart's beats, but that this 

 effect is not constant. 5 Much more marked increase follows irritation of 

 the communicating filaments running between the spinal cord and the in- 



1 Meyer (Op. cit.) in pigeons and rabbits. Masoin (Op. fit.) and Arloing and 

 Tripicr (Op. cit.) state that of the left. Though coursing in the trunk of the vagus, 

 tlio inhibitory nerves seem really to be derived from the spinal accessory, since if the 

 h'lires of the spinal accessory, which Bernard has shown spring from the medulla oh- 

 longata and join the vagus, be torn out, it will be found impossible to arre.-t the 

 heart's action by irritation of the vagus trunk, even as early as three days after the 

 operation, that is befory degeneration of the nerve's fibres could have set in (Bru'cke, 

 Vorlesungen, 1874, Bd. ii, p. 9-lj, though it can be immediately produced by irrita- 

 tion of the opposite vagus. 



2 Lud wig's Arbeiten, 1869. 



3 Muller's Archiv, 1841, Heft 3 ; and Brit, and For. Med. Rev., Oct. 1841. It 

 may be surmised that in many cases of angina, pectoris, in which no lesion adequate 

 to account for death could be discovered, some all'ection of the cardiac plexus might 

 have been traced on more careful examination. 



' .lenaische, Zeits., 18(55, p. :!84 



5 See the researches and experiments of A. v. Bezold, Untersuchungen iiber die 

 Iniiervati-m d. Her/, , Leip/.ig, ISi;:', ; Ludwigand Thiry , Sit/., d. k. Akad. zu Berlin, 

 Bd. xlix ; Cyon, Sitx.. d. k. Sachs. -(iesell. d. Wiss., 1866, and Comptes Rendus, ]sr,7, 

 pp. (',70:1111! Kll'.l; Karl Bever, Wmv.burg Medicin. /eit>ch., I5d. vii.p. 215; Ruther- 

 I'ord, Tran-act. Roy. Sou. Edin., 1870, vol. xxvi, p. i, and his excellent Lectures in 

 the Lancet, in 1871-72. 



