320 OF THE CIRCULATION OF THE BLOOD. 



was 7 beats, or -Jgth of the whole; that between sitting and lying was 4, or 

 ^th of the whole; and that between standing and lying was 11, or -|-th of the 

 whole. Dr. Ed. Smith has made similar and very extended observations on 

 Adults in Phthisis and on Children in health; and conjoined with them the 

 influence of period of the day. He found in Phthisis, at 8 A.M., the in- 

 crease, on assuming the sitting and standing postures, was in each case 10 

 pulsations per minute, but at 4 P.M. it was reduced to 7, and on the whole 

 average there was an increase of 8^ pulsations in each posture. In healthy 

 Children, at 8 A.M., 12 (noon), 5 P.M., and 8 P.M., the increase in the sitting 

 posture was 12:9: 7.3 : 3.5 pulsations, whilst in the standing posture it 

 was 27 : 14.6 : 12 : 10 pulsations per minute: results which seemed to show 

 that the irritability of the heart, augmented by the rest and quiescence of 

 sleep, undergoes a gradual diminution through the day. In both sexes, the 

 effect produced by change of posture increases with the usual frequency of 

 the pulse, whilst the exceptions to the general rule are more numerous, as 

 the pulse is less frequent. The variation is temporarily increased by the 

 muscular effort, involved in the absolute change of the posture; and it is 

 only by the use of a revolving board, by which the position of the body can 

 be altered, without any exertion on the part of the subject of the observation, 

 that correct results can be obtained. That the difference between standing 

 and sitting should be greater than that between sitting and lying, is what we 

 should expect, when we compare the amount of muscular effort required in 

 the maintenance of the two former positions respectively. A different ex- 

 planation has, however, been offered by Ludwig, who considers that the 

 slowing of the pulse which occurs in the recumbent position is due to excita- 

 tion of the vagal roots from increased blood-pressure in the medulla, and Dr. 

 Bruntou has observed that if whilst in the recumbent position the head be 

 held much lower than the body the pulse becomes greatly accelerated, pos- 

 sibly from excitation of the accelerator centres in the medulla. It is stated 

 by Lichteufels and Frohlich that the alternate contraction and relaxation 

 of any set of muscles has a much greater effect than their simple tonic con- 

 traction in increasing the action of the heart. 1 



e. The pulse is well known to be much accelerated by Mental Excitement, 

 especially by that of the Emotions ; it is also quicker during Digestion. 

 The ingestion of warm food produces this effect much more rapidly than cold; 

 and according to Budge, 2 whilst animal food raises the frequency of the pulse 

 more quickly than vegetable, the effect of the latter is much greater and 

 more permanent. Lichteufels and Frohlich found that, an hour and a half 

 after breakfast, the pulse was 13 beats per minute quicker than before, 

 whilst there was only an increase of 9 beats an hour after dinner. The pulse 

 was less frequent in vegetarians, however, than in those who fed on animal 

 diet, and was probably less energetic. The ingestiou of large quantities of 

 water diminishes the frequency of the pulse (Bocker). Dr. Ed. Smith as- 

 certained the rate at each hour of the 24 hours for 3 days successively in 

 health and for six days in Phthisis. He found that it was never stationary, 

 but that there was a progressive increase after a meal and decrease before a 

 meal, so that there were four maxima and four minima daily. The maxima 

 occurred about two hours after a meal, and were the greatest after breakfast 

 and after tea. The day minima immediately preceded the meals, and all 

 were nearly equal. The pulse invariably fell after 9 P.M., so that supper 

 produced but little effect; and the lowest point of the 24 hours was from 3 

 to 5 A.M. There was an increase in the morning with sunlight, The dif- 



1 Donk. d. kais. Aknd. d. Wissens. zu Wien, 1852, t. iii, pt. ii, p. 149. 



2 Physiologic, 1801, p. '275. 



