ACTION OF THE HEART. 321 



ference between the maximum of the day and the maximum of the night 

 amounted in health to from 14 to 34 pulsations, and in Phthisis to from 22 

 to 45 pulsations. The increase from that of the night to the breakfast maxi- 

 mum was, on the average, 27 pulsations in phthisis. There was a considera- 

 ble increase in children whilst eating. During a fast of 24 hours the 

 variation in the rate was. small, but there was an increase during the usual 

 meal hours and an increase at night. 



/. The pulse varies also with the Season, and Dr. Ed. Smith has shown by 

 daily experiments throughout the year, that the rate of pulsation is greater 

 iu the Spring and Summer than in the Winter, both in health and Phthisis. 

 In experiments made upon Frogs, Budge 1 and Calliburces found that im- 

 mersion of the excised Heart or of the hind legs in warm water increased 

 the frequency of the pulse ( 243) ; the same result was obtained after sec- 

 tion of the Crural Nerves, or after poisoning by Woorara, showing that it 

 was not effected through the nervous system. 



g. Variations in the pressure of the surrounding atmosphere exert a cer- 

 tain, but not very well-ascertained influence on the frequency of the Pulse. 

 Alpine travellers are well acquainted with the increased rapidity of the 

 pulse which occurs on attaining great heights; but this is probably in great 

 measure attributable to the great muscular exertion previously made. Sal- 

 vatore Tommasi, however, observed an increase of 8 in the number of his 

 pulsations, after a good night's rest iu the Alpi di Susa, at an elevation of 

 between seven and eight thousand feet. 2 In some experiments performed by 

 Yivenot 3 on the effects of compressed air, in which the barometer rose from 

 742 mm. to 1060 mm., the pulse was observed to rise 3.45 beats on an ave- 

 rage of 79. After exposure for an hour and a half to the maximum of pres- 

 sure it rose to 6.33 beats, and to 7.31 beats on return to the ordinary pres- 

 sure. In other experiments on the influence of rarefied air, the barometer 

 falling from 758 to 500 mm., there were observed an increase in the ampli- 

 tude of the radial tracings, as shown by the sphygmograph, indicative of 

 diminution of vascular tension ; increased feeling of warmth in the skin, 

 especially of the face; congestion of the conjunctiva; uneasiness in the head, 

 difficulty of thinking, and neuralgic pains in the forehead, neck, and teeth; 

 all which symptoms appeared to arise from derivation of the blood to the 

 cutaneous capillaries. On gradual readmission of the air they soon van- 

 ished. Jamiuet 4 had the opportunity of examining the effects of compressed 

 air on many workmen engaged in the construction of the Illinois and St. 

 Louis Bridge over the Mississippi River. In this work the men were ex- 

 posed to a pressure at one time of 50 Ibs. to the square inch, exclusive of the 

 15 Ibs. of the ordinary ambient atmosphere. It was found necessary at an 

 early period to construct an air-lock or intermediate room, where the passage 

 into air of ordinary pressure could be gradually effected, otherwise most 

 serious symptoms, great muscular exhaustion, headache, epigastric pain, sick- 

 ness, paralysis, haemorrhage, and even death resulted. M. Jaminet found an 

 increased frequency of the pulse and respiration during the first few minutes, 

 the pulse rising about 15 beats above the normal ; but after remaining iu the 

 air-chambers for two hours, and whilst still exposed to the action of the in- 

 creased pressure, the pulse fell about 15 beats below the normal. On issu- 

 ing into the open air the pulse again rose to 15 or 20 beats above the normal, 

 and slowly in the course of an hour or two returned to its usual state. 



1 Physiologic. 1861, p. 272. 2 Fisiologia, 1861, p. 244. 



3 Virchow's Archiv, xxxiv, p. 515. See also the Essays of Bucquoy and Pravaz, 

 on this subject. 



4 A. Jaminet, On the Physical Effects of Compressed Air on Man, etc. (Pamphlet) 

 1871, pp. 135. 



