MOTION OF THE BLOOD IN THE VESSELS. 373 



494. The Pulse is well known to be much accelerated by Mental excite- 

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

 but on neither of these points can any exact numerical statement*be given. 

 The diurnal variation of the pulse, however, has been made the subject of 

 observation by Dr. Guy ;* and, as the result of his inquiries have much in- 

 terest, although (from having been made only on his own person) they may 

 ultimately require some modification, they will be here stated. " 1. The pulse 

 of a healthy male in a state of rest, unexcited either by food or exercise, is 

 most frequent in the morning, and gradually diminishes as the day advances. 

 2. The pulse diminishes in frequency more rapidly in the evening than in 

 the morning. 3. The diminution in the frequency of the pulse (after excite- 

 ment) is more regular and progressive in the evening than in the morning. 

 4. The effect of food is greater and more lasting in the morning than in the 

 evening ; and in some instances, the same food, which in the morning pro- 

 duces an effect considerable both in amount and duration, has no effect what- 

 ever in the evening." It may be hoped that, ere long, this interesting and 

 important subject will receive further elucidation. 



[Dr. Valleix has recently publishedf a series of interesting observations on the fre- 

 quency of the pulse in newly-born infants, and in children aged from seven months to 

 six years. He obtained the following results: 1. At birth the pulse is less frequent than 

 at six months; the number of beats in a minute may be stated with considerable exact- 

 ness to be between 90 and 100. 2. Increase of temperature, even in the slightest degree, 

 invariably produces a notable acceleration of the pulse. The exact ratio between the 

 degree of elevation of temperature and the increase in the frequency of the pulse, is not 

 yet accurately ascertained. 3. Although the observations of Dr. Valleix show a progres- 

 sive diurnal diminution in the frequency of the pulse, still, he thinks, that it would be 

 premature to conclude that these facts support those of Dr. Guy. Dr. Valleix examined 

 his patients in the morning after they had been eating, and to this fact, he thinks, should 

 be attributed the acceleration of the pulse in the early part of the day, and its subsequent 

 diminution, towards evening. 4. The slightest muscular effort in children is sufficient to 

 augment considerably the number of pulsations. The same is true of any moral emo- 

 tion. 5. The influence of sex on the pulse is very marked in young children. The pulse 

 is much more frequent in young girls than in boys of the same age. 6. During sleep 

 there is a decided diminution in the number of beats. 7. Between 7 and 27 months 

 there is no sensible change in the frequency of the pulse. Its mean may be stated at 

 126 beats in the minute, without distinction of sex. If sex be considered, it would be 121 

 for males and 128 for females. These numbers express the frequency of the pulse at 

 this age under ordinary circumstances, but if a state of perfect calm is supposed, the 

 numbers would be 119 for the males, and 124 for females. 8. After some observations, 

 not very numerous, however, the pulse would appear to range a little above 100 till six 

 years of age. 9. The mean number of inspirations in a minute in children aged from 7 

 months to two years and a half, is between 30 and 32, and is to number of pulsations : : 

 1 : 4. M. C.] 



III. Causes influencing the Circulation in the Arteries and Capillaries. 



495. That the movement of the Blood through the Arterial trunks and the 

 Capillary tubes is, in Man, and in other warm-blooded animals, chiefly de- 

 pendent upon the action of the Heart, there can be no doubt whatever. It can 

 be easily shown by experiment, that, if the Arterial current be checked, the 

 Capillaries will immediately cease almost entirely to deliver the blood into the 

 veins, and the Venous circulation will be instantaneously arrested. And it 

 has also been proved, that the usual force of the Heart is sufficient to propel 

 the blood, not only through the Arterial tubes, but through the Capillaries, 

 into the Veins ; since even a less force wityserve to propel warm water through 



* Op. cit., vol. iv. p. 69. 



f [Memoires de la Societe Medicale d'Observation de Paris. Tome Deuxieme, IS 

 p. 300, et seq.] 

 32 



