1873.] 



on the Temperature and Circulation. 



379 



does not exhaust the heart, as a walk, or holding up a weight for a short 

 time, developes the tracing instead of making it smaller. This is well 

 seen in Obs. D, E, P, Gr, where the greater rise implies that the 

 artery is relaxed, but the heart not weakened. It is also well seen in 

 cases where the exercise is more severe, as VI. and XIII., but where 

 the heart possesses much reserve force ; and is well exemplified in an in- 

 teresting observation published by Dr. Eraser (Journ. of Anat. and Phys. 

 1869, hi. p. 128), where a tracing is given showing the effect of hard rowing. 

 The after-tracing is much more ample than the one before, like VI., but 

 differs from this in having a rounder top and a more notched fall, i.e. in. 

 showing more dicrotism. "Where both heart and artery have been 

 weakened, the heart seems to recover sooner than the artery ; this is 

 well shown by the tracings taken in a case where nitrite of amyl was in- 

 haled. That taken immediately after the inhalation is irregular, and much 

 smaller than the one taken before ; while the third, taken two min utes 

 after the inhalation, is quite remarkable for the height of its rise and the 

 length of the fall preceding the notch. The height of the rise before the 

 amyl was given is -3 inch, that immediately after is about *175, while the 

 third is nearly -6 in. Clearly the artery yielded more on the last occasion 

 to the impelling force of the ventricle than it had done on the first. 

 Expenditure of force seems to produce the same effect. In obs. C, h, the 

 tracing taken two or three hours after rowing is much ampler than that 

 taken immediately after. In XII. the tracing taken thirty minutes after 

 run is decidedly ampler than that taken directly after. 



Severe exertion seems to exhaust the heart and render it less capable 

 of distending the artery. M. Lortet, in his ascents of Mont Blanc, found 

 his pulse at high elevations febrile, rapid, and so miserable that it was 

 scarcely able to raise the spring of his sphyginograph. In most of my 

 observations the tracing taken as soon as possible after the exercise is 

 smaller than that taken during quiescence. This is very specially the 

 case in IV., where the man was out of condition, and became prostrate 

 and sick after the run ; it seems, however, to be the rule, except in in- 

 dividuals whose hearts are gifted with more than usual staying-power, 

 such as in VI. and VIII. Prolonged exertion, though not severe, if I 

 may judge from one observation, also weakens the heart and di mini shes 

 the tracing. 



The general conclusion I am inclined to come to is, that the amplitude 

 of the tracing depends partly on the force with which the heart is acting, 

 and partly on the relaxation of the artery. As, however, in all cases of 

 severe exertion there must be considerable expenditure of force, and as 

 at the same time the blood-flow is certainly promoted in the extremities 

 and at the surface, it can hardly be doubted that the arteries, the larger 

 and smaller, are relaxed, and that the size of the tracing is therefore 

 mainly dependent on the amount of cardiac force exerted, which is 

 but slightly opposed by resistance of the arterial coat. 



