. Animal physiology. Physiology, Comparative. MECHANISM OF THE HExVRT. 233. Fig. 126. against the walls of the chest; and it is by the same action that the pulse in the arteries is produced (§ 276V 270. The combined actions of each auricle and its ventri- cle, may be illustrated by an apparatus like that repre- sented in fig. 126. It con- sists of two pumps, a and h, of wliicli the pistons move up and down alternately ; and these are connected with a pipe c f, in which there are two valves d and e, opening in the direction of the arrow. The portion c of the pipe represents the venous trunk by
. Animal physiology. Physiology, Comparative. MECHANISM OF THE HExVRT. 233. Fig. 126. against the walls of the chest; and it is by the same action that the pulse in the arteries is produced (§ 276V 270. The combined actions of each auricle and its ventri- cle, may be illustrated by an apparatus like that repre- sented in fig. 126. It con- sists of two pumps, a and h, of wliicli the pistons move up and down alternately ; and these are connected with a pipe c f, in which there are two valves d and e, opening in the direction of the arrow. The portion c of the pipe represents the venous trunk by which the blood enters the heart; the pump a represents the auricle, and the raising of its piston enables the fluid to enter and fill it. When its piston is lowered, its fluid is forced through the valve d into the pimip h .(which represents the ventricle), whose piston rises at the same time to receive it; and when this piston is lowered in its turn, the fluid (being prevented from returning into a by the closure of the valve d) is propelled through the valve e into the pipe /, which may represent an arterial tube; whilst at the same time a fresh supply of blood is received into the pump a by the raising of its piston. 271. The number of contractions of the heart ordinarily taking place in an adult man, is from 60 to 70 per minuta It is usually rather greater in women; and in children it is far higher, being from 130 to 140 in the new-born infant, and gradually diminishing during the j^eriod of infancy and child- hood. It is rather gi-eater in the standing than in the sitting posture, and in sitting than in lying down : it is increased by exercise, especially by ascending a steep hill or going upstairs, and also by any mental emotion. It is important to remember these facts, in reference to the management of those who are suffering under diseases of the heart or of the lungs, which prevent the ready passage of the blood through these organs ; for if more blood be brought to
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Keywords: ., bookauthorcarpente, bookcentury1800, bookdecade1850, bookyear1859
