154 PHYSIOLOGY ASD HEALTH. 



353. The quantity of this insensible perspiration varies 

 from thirty ounces a day in the northern, to forty ounces a 

 day in the southern, countries of Europe. Carpenter esti- 

 mates it to be thirty-three ounces in England ; this is eleven 

 grains a minute; others give a much higher estimate. Cruik- 

 shank's experiments demonstrated it to vary from twelve to 

 forty-five grains a minute ; and he assumes the mean, from 

 persons of both sexes, of average size, and in good health, 

 to be twenty-three grains a minute. Taking the last as the 

 standard, and adding these twenty-three grains to the five 

 grains and two thirds of vapor thrown out from the lungs, 

 we have enough to saturate somewhat more than two feet 

 of air with moisture ; and, so much air being saturated, it 

 can take no more vapor from the lungs. 



354. Thus we see that, in these three ways, the air loses 

 its power of relieving the blood of its superfluous carbon and 

 water, and is thereby rendered unfit for the work of respira- 

 tion ; first, by the loss of its oxygen, in each minute, 

 720 inches ; secondly, by saturation with carbonic acid gas, 

 1800 inches; thirdly, by saturation with vapor from the 

 lungs and skin, 3590 inches. 



CHAPTER XII. 



Seven to ten Feet of Air spoiled each Minute. Want of fresh Air 

 in Houses, but not provided. Size of Parlors, and Number of 

 Occupants. Small Sleeping-Chambers. Lodging-Rooms in 

 Boarding Houses, and in temporary Houses. Cabins of Steam 

 and Canal Boats. 



355. About four cubic feet of air being rendered by each 

 person partially or entirely useless for the purpose of purifying 

 the blood and giving it new life, it will, of course, be neces- 

 sary that we have so much new and fresh air supplied every 

 minute for each one. If this, after having been once breathed, 

 or saturated with vapor, were carried immediately away, this 



