QUANTITY OF AIR EESPIRED. 2O3 



is diminished at the rate of one cubic inch for every addi- 

 tional pound up to 196 pounds, or 14 stones; so that, for 

 example, while a man of five feet six inches, and weighing 

 less than nj- stones, should be able to expire 217 cubic 

 inches, one of the same height, weighing I2|- stones, might 

 expire only 203 cubic inches. 



By age, the capacity appears to be increased from about 

 the fifteenth to the thirty-fifth year, at the rate of five 

 cubic inches per year, from thirty-five to sixty-five it 

 diminishes at the rate of about one and a-half cubic inch 

 per year ; so that the capacity of respiration of a man of 

 sixty years old would be about 30 cubic inches less than 

 that of a man forty years old, of the same height and 

 weight. 



Mr. Hutchinson's observations were made almost exclu- 

 sively on men ; and his conclusions are, perhaps, true of 

 them alone ; for women, according to Bourgery, have only 

 half the capacity of breathing that men of the same age 

 have. 



The number of respirations in a healthy adult person 

 usually ranges from fourteenjo eighteen_er minute. 



It is greater in infancy and childhood ; and of course 

 varies much according to different circumstances, such as 

 exercise or rest, health or disease, etc. Variations in the 

 number of respirations correspond ordinarily with similar 

 variations in the pulsations of the heart. In health the 

 proportion is about I to 4, or I to 5, and when the 

 rapidity of the heart's action is increased, that of the chest 

 movement is commonly increased also ; but not in every 

 case in equal proportion. It happens occasionally in 

 disease, especially of the lungs or air-passages, that the 

 number of respiratory acts increases in quicker proportion 

 than the beats of the pulse ; and, in other affections, much 

 more commonly, that the number of the pulses is greater 

 in proportion than that of the respirations. 



According to Mr. Hutchinson, the force with which the 



