IX 



CAEDIAC MUSCLE AND NERVES 



331 



stimulation. It should, however, be stated that the experimental 

 data of Baxt, and his interpretation, have to some extent been 

 corrected by the subsequent work of Meltzer (1897), Reid Hunt 

 (189*7), and Engelmann (1900) ; who demonstrated that the effects 

 consequent on the simultaneous stimulation of the two distinct 

 cardiac nerves are more varied and complex than was supposed by 

 Baxt, and that the chrono- and iso tropic may be complicated by 

 dromotropic effects. 



X. After defining cardiac inhibition due to stimulation of the 

 vagus as a diastolic effect, in so far as it favours diastole and 



FIG. 153. Diagram representing frequency of cardiac beats after excitation of vagus (continuous 

 broarl line), accelerator nerves (continuous thin line), and of both nerves (dotted line). 

 (Baxt.) The stimulation of the accelerators lasts from a to e, (16"), that of the vagus from d 

 to e (4"), and commences 12" later. Time marked in seconds on the abscissa ; number of beats 

 occurring in each 2" shown on areas of ordinates. 



obstructs systole, and the acceleration due to the sympathetic as a 

 systolic effect, in-so far as it favours systole and obstructs diastole, 

 we still have no definite idea of the inner mechanism of these 

 phenomena. As, according to the supporters of the myogenic 

 doctrine, the automatic rhythm of the heart is a property inde- 

 pendent of the nervous system, inherent in the muscle cells of the 

 myocardium, it is logical to assume that the two kinds of nerve 

 which influence the heart from without determine opposite results, 

 inasmuch as they alter the metabolism of the muscle cells which 

 underlies autoinaticity in an opposite direction. This was 

 established by Gaskell (1887) in his important discovery of the 



