ACTION OF THE HEART. 309 



for 1 2 minutes, and then the heart passed through the same stages that it 

 would otherwise have presented, if it had been gradually warmed It thus 

 appears that if the temperature be raised above that of "heat-diastole" 

 "heat-rigor" is produced, and the movements of the heart cannot again be 

 restored by cooling it. The excitability of the inhibitory nerve apparatus is 

 abolished during the arrest of the heart's action from the heat, for Cyon 

 has shown that irritation of the sinus venosus, which invariably produces 

 arrest of the heart's action in diastole under normal conditions, causes tetanus 

 of the ventricle when applied to a heart that is iu a state of arrest from heat. 

 In warm-blooded animals the frequency of the heart's beats also increases 

 with the temperature within certain limits (Panum, Brunton). In one in- 

 stance, by means of registering apparatus, Dr. Brunton found that the heart 

 of a rabbit, when the animal was exposed to a temperature of 105 F., beat 

 472 times in a minute. After reaching a maximum the beats become slower, 

 and the heart finally stops. The increase is not the same for each degree of 

 rise in the temperature; and the number of beats at the same temperature, 

 and also the amount of quickening for each degree of rise of temperature, 

 differs in different animals. The upper limit at which the heart stands still 

 in rabbits is about 113 or 114 F. (Brunton) ; as the temperature to which 

 the heart is exposed rises, and the pulse quickens, the inhibitory power of 

 the vagus diminishes, but when the temperature had risen in Dr. Bruntou's 

 experiments to nearly its upper limit, the power of the vagus was again 

 observed to be increased, and contrary to expectation to be strongly 

 marked just before the heart ceased to beat. It is not improbable that the 

 increased frequency of the heart's action in febrile conditions of the system 

 is in part due to the stimulating effect upon the heart of the increased tem- 

 perature of the blood caused by augmented tissue-change. 



244. Nerves Retarding or Inhibiting the Action of the Heart. Some years 

 ago (1846) the brothers Weber 1 observed the important fact which proved 

 the starting-point of numerous researches on the influence of the nervous 

 system upon the heart, that irritation of the Vagus, or of its inferior cut 



1 Archiv. d'Anat Gen. et de Physiol., Jan. 1846, and Warner's Handworterbuch, 

 Bd. iii, p. 31 ; see also Budge in Archiv. f. Phys. Heilk., 1846/Bd. v, p. 319 ; v. Bezold, 

 Unters. lib. d. Innervat. des Herzens, 1863 ; Rutherford, Influence of the Vagus upon 

 the Vascular System; Transact, of Roy. Soc., Edinb., vol. xxvi, 1870, p 1 (in this 

 paper references will be found to all the more important antecedent memoirs) ; Goltz, 

 Centralblatt, 1*68, P- 593; Meyer, Das Hemmungsnerven-system des Herzens, 

 Berlin, 1869 ; Abstract in Journ.'of Anat. and Physiol., 1869, vol. iii, p. 445 ; Kowa- 

 lowsky and Adamuk, Centralblatt, 1868, p. 546; Bernbardt, Inaug. Dissert., 8vo., 

 p. 32,1868; Aubert and Pvoever, Centralblatt, 1868, p. 578; Coats, Bericht d. k. 

 Sachs. Gesell. d. Wissenschaft, 1869 ; also the Effects of Irritation of the Vagus on 

 the Internal Work of the Heart, Leipziger Arbeiten, Bd. iv, 1870, p. 176; Michael 

 Foster, Fullerian Lectures, Rev. des Cours Scientif., 1869, Nos. 42, 43, and 45; P. 

 Keuchel, Das Atropin, und die Hemmungsnerven, Inaug. Dissert., 1868; Donders, 

 Centralblatt, 1870, p. 408; Masoin, Bull, de 1'Arad. Roy. de Med de Belirique, t. vi, 

 p. 4, 1872-3 ; Nuel. Pfliiger's Archiv, Bd. ix, p. 83 ; Boehm, Studien liber Herzgiften, 

 1871 ; Arloin et Tripier, Archiv. de Phys. Norm, et Path., 1872, Contribution a la 

 Physiologie des Nerfs Vagues; Schiff, Herz- und Gefass-nerven, abstract in Central- 

 blatt, 1873, Nos. 1, 2, 3; Metschnikoff and Setschenow, Ueber die Vaguswirkung auf 

 das Herz, Centralblatt, 1873, pp. 163 and 289 ; Schiff, Archiv f. Physiol. Heilk., 8ter 

 Jahr. ; Moleschott, Wiener Med. Wochens., 25th May, 1861 ; and Lister, Proceed. 

 Roy. Soc., vol. ix. p. 367, were led by their researches _ to consider the vagus as a 

 motor nerve of extreme excitability, but which was easily exhausted.^ They main- 

 tained that with very feeble currents applied to it, the heart's action is accelerated ; 

 but Pfliiger, v. Bezold, Rutherford, Wundt, and many others have been unable to 

 corroborate these statements. Later experiments have shown, however, that certain 

 accelerator fibres do run in the trunk of the vagus; see Schiff's Physiologie, 1859, 

 p. 417 et seq. 



