656 SPECIAL PHYSIOLOGY. 



warm bath, and by the influence of long-continued exposure to cold; 

 but the sudden and brief application of cold, accelerates the beats of 

 the heart. Elevation above the level of the sea in other words, a 

 diminution of the atmospheric pressure is found to increase the beats 

 of the heart ; thus, Dr. Frankland, whose natural pulse is 60, found 

 that after six hours' sleep on the summit of Mount Blanc, thus ex- 

 cluding the effects of recent muscular effort, his pulse was 120 per 

 minute ; on reaching, in the descent, the so-called Corridor, it was 

 108 ; at the Grand Mulet it was 88 ; and at Chamounix it was 56. 

 As one effect of high elevation is to increase the frequency of the 

 respiration, in consequence of the greater tenuity of the atmosphere, 

 and, as a relation exists between the frequency of the heart's action 

 and the respiratory movements, the increased rapidity of the pulse in 

 elevated positions may thus be partly explained. An increase in the 

 density of the atmosphere, such as takes place in a submerged diving- 

 bell, is said to lower the frequency of the pulse, and also the move- 

 ments of respiration. An increase of barometric pressure of th 

 of the normal pressure, lowers the pulse, on an average, ten beats per 

 minute, whilst the respirations are simultaneously lessened by two. 

 (Vivenot.) 



The normal relation between the number of respirations and the 

 heart's beats is, on an average, 1 to 4 ; in diseased conditions, this 

 ratio is often interfered with, but it is preserved in those accelerations 

 or retardations of the breath and pulse, which take place in the healthy 

 state, such as those due to exercise, change of posture, food, stimu- 

 lants, and emotion, or to the opposite conditions of rest, abstinence, 

 or depressing influences. Thus, if the normal respirations were 16 

 per minute, the pulse would be about 64 ; and if the former were in- 

 creased to 18 or 20, the latter would be raised to 72 or 80. Expira- 

 tion diminishes, and inspiration increases, the frequency of the pulse. 



A certain relation appears to exist between the facility or the diffi- 

 culty of the capillary circulation, and the rapidity or slowness of the 

 heart's action ; and this may explain some of the preceding phenomena. 

 Thus, the application of cold to the surface of the skin, limiting or 

 checking the circulation through the systemic capillaries, by contract- 

 ing the small arteries, is accompanied by a retardation of the heart's 

 beats ; a state of repose acts, but less powerfully, in the same way. 

 A feeble and slow respiration, lessening the capillary circulation 

 through the lungs, has a similar effect ; so also has holding the breath. 

 On the other hand, exercise and heat quicken the systemic capillary 

 circulation, and also increase the frequency of the ventricular sys- 

 toles, and so does a quickened and active condition of the respiration. 

 Any obstacle to the flow of blood through the vessels, and thereby to 

 the action of the ventricles, appears therefore to be sympathized with, 

 and a reduction of the heart's beats is the result ; whilst the removal 

 of such obstacles is followed, in like manner, by the greater rapidity 

 of the beats. Exercise, excitement, and food, probably, also act on 

 the heart, by producing a greater flow of blood to that organ. 



Not only the frequency, but the force of the heart's beats, may be 

 modified by external or internal circumstances. This force is increased 



