326 CIRCULATION OF NUTRITIVE FLUID. 



Age. The pulse of the newly-born infant averages from 130 to 140 

 per minute ; and this rate gradually diminishes, until, in adult age, the 

 pulse averages from 70 to 80 ; and in the decline of life from 50 to 65. 



$ ex . The pulse of the adult female exceeds that of the adult male 

 in frequency, by about 10 or 12 beats in a minute ; and it is also more 

 liable to disturbance from other causes. 



Muscular Exertion. The effect of this in accelerating the pulse is 

 well known ; but as the amount of change depends upon the degree of 

 exertion, no general statement can be made on the subject. The con- 

 tinued influence of a moderate degree of muscular exertion, is shown by 

 the effect of posture upon the pulse. Thus the pulse is on the average 

 from 7 to 10 beats faster (per minute) in the standing than in the sitting 

 posture ; and 4 or 5 beats faster in the sitting than in the recumbent 

 posture. This amount of variation is temporarily increased by the 

 muscular effort required for the change of posture ; but this soon sub- 

 sides into the continued rate, which the permanent maintenance of the 

 new posture involves. There are certain states of the system, in which 

 the heart's action is increased to a most violent degree, by a simple 

 change of posture ; and in which, therefore, it is necessary that even 

 this slight movement should be made with gentleness and caution. 



Mental Condition. The action of the heart is peculiarly influenced, 

 as every one is aware, by the excitement of the emotions. This is a 

 fact to which, however familiar, the medical practitioner should con- 

 stantly direct his attention. The trifling agitation occasioned by the 

 entrance of the medical man will produce, in many patients, such an 

 acceleration of the pulse, as would be very alarming, if its true cause 

 were not known. And the real rate of the pulse cannot be ascertained, 

 until time has been permitted for the agitation to subside ; which is 

 favoured, also, by the influence of a gentle manner and tranquillizing 

 conversation. The operation of the intellectual powers does not seem 

 to affect the rate of the heart's movement in any other way, than by 

 inducing a general state of feverislmess, if it be too long or too ener- 

 getically kept up. 



State of the Digestive System. The pulse is quickened during the 

 digestion of a meal ; but no exact numerical statement can be made on 

 this subject. 



Period of the Day. The frequency of the pulse appears to be some- 

 what greater in the morning than it is in the evening ; and the tem- 

 porary action of any of the preceding causes, more quickly subsides in 

 the evening than in the morning. 



580. The movements of the heart have been supposed to depend 

 upon a constant supply of nervous influence, generated by the cerebro- 

 spinal system, and transmitted through the sympathetic nerve, the 

 branches of which are copiously distributed to it. And this idea 

 seemed to derive support from the fact, that, when the brain and 

 spinal cord are removed, or when large portions of them are suddenly 

 destroyed, by crushing or by the breaking-up of their substance in any 

 other mode, the movements of the heart are arrested. But it has 

 been shown that the brain and spinal cord may be gradually removed, 

 without any such consequence ; and the occasional production of foetuses 



