380 Dr. C. H. Jones on the Effects of Exercise [June 19, 



Cases II. and IX. are, however, a great puzzle. Here, especially in 

 II., the tracing is more ample before than after the run ; yet the sphyg- 

 mometer shows that in the latter period the heart is not acting more 

 feebly, but the reverse. This discrepancy is, I fear, not to be got over by 

 the consideration that the height of the ascent does not depend so much 

 on the whole amount of force put forth by the heart in a single contrac- 

 tion as on the amount put forth at a given instant. The artery remain- 

 ing the same, a powerful contraction of the ventricle taking place gradu- 

 ally may no doubt produce a lower and more sloping rise than a less forcible 

 one, which takes place more suddenly. Dr. Sanderson writes that 

 " suddenness of contraction manifests itself in vertically and amplitude 

 of the primary ascent of the tracing, while in those forms of pulse which 

 correspond to a more gradual mode of contraction the first event is in- 

 distinguishable." But the heart in the cases referred to was assuredly 

 not contracting gradually at the time when the second tracings were 

 taken, but sharply and jerkingly. Although the height of the ascent 

 may be no measure of the increased amount of blood in the artery, yet it 

 is, I must think, of the force applied at each systole to the inner surface 

 of the artery and of the expansion of its tube. A sharp flick against 

 the pad of my sphygmometer, which (the pad) is not allowed to move 

 more than a certain distance, will drive the traveller the whole length of 

 the scale, while a pressure less sharply and suddenly applied will not 

 send it nearly so far. In any case, therefore, where, the artery remaining 

 in the same state, or, a fortiori, having its contractility lessened, the rise 

 is positively lowered in a tracing as compared with a previous one, I 

 believe that weakening of the cardiac force is indicated ; at least this is 

 the only interpretation I can put on my observations. The assumption 

 of a tightened artery would solve the difficulty above stated ; but, under 

 the circumstances, this seems so improbable that I cannot think such con- 

 striction existed. 



The general conclusions as to the effect of exertion on the circulation 

 and temperature which may be deduced from the foregoing observations 

 are these : — 



(1) That the heart's force is, in most cases, more or less weakened by 

 great exertion. (2) That the arterial contractility is probably always 

 lessened, even when the exertion is moderate. (3) That after exhaustion 

 the heart recovers sooner than the artery. . (4) That the heart's action, 

 in about one third of the cases of severe but brief exertion, is increased 

 in force. (5) That the acceleration of the pulse probably depends chiefly 

 on exhaustion of the vagi. (6) That acceleration of pulse-rate has per se 

 no effect in increasing intravascular pressure. (7) That the temperature is 

 usually elevated by exercise from -36° to 1°'8 I\, but in rare instances, 

 or after prolonged toil, may be lowered l°-08 to 2°-16 F. (8) That the 

 paresis of cardiac and heat-regulating centres, coinciding with consump- 

 tion of nerve-force in motor centres, shows, that, in some way one centre 



