INFLUENCE OF RESPIRATION ON THE HEART 43 



muscular effort required to maintain the body in the sitting and stand- 

 ing positions. The following are the results of experiments bearing on 

 this point. 



" i. Difference between the pulse in the erect posture, without 

 support, and leaning in the same posture, in an average of twelve ex- 

 periments on the writer, 12 beats; and on an average of eight experi- 

 ments on other healthy males, 8 beats. 



" 2. Difference in the frequency of the pulse in the recumbent pos- 

 ture, the body fully supported, and partially supported, 14 beats on an 

 average of five experiments. 



" 3. Sitting posture (mean of ten experiments on the writer), back 

 supported, 80 ; unsupported, 87 ; difference, 7 beats. 



" 4. Sitting posture with the legs raised at right angles with the body 

 (average of twenty experiments on the writer), back unsupported, 86 ; 

 supported, 68 ; difference, 18 beats. An average of fifteen experiments 

 of the same kind on other healthy males gave the following numbers : 

 back unsupported, 80; supported, 68 ; a difference of 12 beats." 



Muscular exercise increases the frequency of the pulsations of the 

 heart ; and the experiments just cited show that the difference in rapidity, 

 which is by some attributed to change in posture, some positions, it 

 is fancied, offering fewer obstacles to the current of blood than others, 

 is due mainly to muscular exertion. According to Bryan Robinson 

 (1734), a man in the recumbent posture has 64 pulsations per minute; 

 sitting, 68 ; after a slow walk, 78 ; after walking four miles in an hour, 

 100; and 140 to 150 after running as fast as he could. 



The influence of sleep on the action of the heart reduces itself 

 almost entirely to the proposition that during this condition there 

 usually is entire absence of muscular effort, and consequently the 

 number of beats is less than when the individual is awake. It has 

 been found that there is no difference in the pulse between sleep and 

 perfect quiet in the recumbent posture. This was noted in the 

 adult male ; but there is a marked difference in females and young 

 children, the pulse being always slower during sleep (Quetelet). 



The influence of extremes of temperature on the heart is very 

 decided. The pulse may be doubled by remaining a very few min- 

 utes exposed to extreme heat. . Bence Jones and Dickinson have ascer- 

 tained that the pulse may be much reduced in frequency, for a short 

 time, by the cold douche. It has also been remarked that the pulse is 

 more rapid in warm than in cold climates. 



Influence of Respiration on the Action of the Heart. The relations 

 between the circulation and respiration are very intimate, and one 

 process can not go on without the other. If circulation is arrested, 



