ACCELERATION AND RETARDATION OF PULSE. II J 



upper segment indicates the pulmonary or lesser circulation, 

 the lower the general or systemic circulation. 



Influences which retard or accelerate the beating of the heart. 

 In an adult in a normal condition, the heart beats about 

 sixty times a minute, and the pulse consequently indicates 

 the same number of pulsations, but diverse causes may 

 augment or diminish the frequency of these movements. 

 They become more frequent during digestion, and under the 

 influence of alcohol, coffee, or other excitants; abstinence, 

 on the contrary, retards them. Intellectual labour also accel- 

 erates the action of the heart, but the heart is calmer during 

 sleep, and shares in a measure the repose of the other organs. 

 An unlocked for sight, a word striking the ear, or a thought 

 crossing the mind, will cause strong and rapid pulsations. 

 Eristratus discovered the cause of the malady which threat- 

 ened the life of Antiochus, by placing his hand on the heart 

 of the young prince at the moment that Stratonicea appeared 

 before him. The pulse is accelerated also by muscular 

 exercise, and by violent efforts. But in this case the cause 

 is complex, for the respiration is also more frequent, and this 

 function is one of those which have most influence on the 

 circulation. In ordinary breathing, each inspiration gives 

 more force to the blood in the arteries, and if the respiration 

 becomes more hurried it is recognizable in the pulse. If, on 

 the contrary, respiration is suspended or imperfect, the circu- 

 lation is retarded, and the pulse beats with less force; in a 

 word, in most physiological conditions there is a constant 

 relation between the respiratory movements and the beating 

 of the heart. The alternate expansion and contraction of 

 the walls of the chest are therefore one of the principal 

 causes which affect the circulation, by facilitating the afflux 

 of blood to the thoracic cavity and insuring its expulsion 

 from it. 



The pressure of the atmosphere also influences the beating 

 of the heart, but only under certain conditions. It is not un- 

 common to find in the high valleys among the Alps men whose 

 pulse beats between fifty and sixty times a minute this infre- 

 quency is perhaps more common among mountaineers who 

 live at an altitude of 3280 feet or more, than in less elevated 



