An American text-book of physiology . nspiration about 2000 cubic cen-timeters; during forced expiration it is dimin-ished about 1500 cubic centimeters. Betweenthe extremes of forced inspiration and forcedexpiration the volume diifers about 3J times. Vital capacity is the volume of air that canbe expired after the most forcible obtained by Vierordt from the resultsof the observations by various investigators are3400 cubic centimeters for men and 2500 cubiccentimeters for women. Such investigationsare conducted by the aid of a spirometer (), Avhich is a calibrated ga
An American text-book of physiology . nspiration about 2000 cubic cen-timeters; during forced expiration it is dimin-ished about 1500 cubic centimeters. Betweenthe extremes of forced inspiration and forcedexpiration the volume diifers about 3J times. Vital capacity is the volume of air that canbe expired after the most forcible obtained by Vierordt from the resultsof the observations by various investigators are3400 cubic centimeters for men and 2500 cubiccentimeters for women. Such investigationsare conducted by the aid of a spirometer (), Avhich is a calibrated gasometer consistingof a bell-jar submerged in water and counter-poised. Communicating with the interior ofthe jar is a tube through which the expired air is conducted. The subject makes the deepest possible inspiration and thenforcibly expires into the tube: the jar rises in proportion to the volume ofair admitted, and the extent of this rise may be read from the scale.* Pfliigers An-hiv Jiir Physiolor/ie, 1888, vol. 43, pp. 23G, Fig. 138.—Wintrichs modification ofHutchinsons spirometer. 530 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. Vital capacity is affected by various circumstances, especially age, stature,sex, , occupation, and disease. It increases with age, reaching a maxi-mum at about thirty-five years, after which there occurs an annual decrease ofabout 32 cubic centimeters uj) to about sixty-five years. In proi)ortion tothe length of the body it increases up to twenty-five years and then dimin-ishes. Wintrich has shown that vital capacity for each centimeter of heightvaries at different ages; thus at eight to ten years it is 9 to 11 cubiccentimeters for each centimeter of height, at sixteen to eighteen cubic centimeters, and at fifty years 21 cubic centimeters. Arnoldestimates that in the adult for each centimeter of increase or decrease ofheight beyond a mean standard there is a corresponding rise or fall of 60 cubiccentimeters in men and of 40 cub
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