ACTION OF THE HEART. 135 



somewhat more frequently than in those of the phleg- 

 matic ; and in the female sex more frequently than in the 

 male. 



After a meal its action is accelerated, and still more so 

 during bodily exertion or mental excitement ; it is slower 

 during sleep. The effect of disease in producing tem- 

 porary increase or diminution of the heart's action is well 

 known. From the observation of several experimenters, 

 it appears that, in the state of health, the pulse is most 

 frequent in the morning, and becomes gradually slower 

 as the day advances : and that this diminution of frequency 

 is both more regular and more rapid in the evening than 

 in the morning. It is found, also, that as a general rule, 

 the pulse, especialy in the adult male, is more frequent in 

 the standing than in the sitting posture, and in the latter 

 than in the recumbent position ; the difference being 

 greatest between the standing and the sitting posture. 

 The effect of change of posture is greater as the fre- 

 quency of the pulse is greater, and accordingly, is more 

 marked in the morning than in the evening. Dr. Guy, by 

 supporting the body in different postures, without the aid 

 of muscular effort of the individual, has proved that the 

 increased frequency of the pulse in the sitting and stand- 

 ing positions is dependent upon the muscular exertion 

 engaged in maintaining them ; the usual effect of these 

 postures on the pulse being almost entirely prevented when 

 the usually attendant muscular exertion was rendered un- 

 necessary. The effect of food, like that of change of 

 posture, is greater in the morning than in the evening. 

 According to Parrot, the frequency of the pulse increases 

 in a corresponding ratio with the elevation above the sea ; 

 and Dr. Erankland, who lately passed a night on the 

 summit of Mont Blanc, informed the author, that his pulse 

 was about double the ordinary standard all the time he 

 was there. After six hours' perfect rest and sleep at the 

 top, it was 1 20, on descending to the corridor it fell to 108, 



