EFFECTS OF SUSPENSION OR DEFICIENCY OF RESPIRATION. 409 



327. The determination of the cubic space which ought to be allowed for 

 each person in workhouses, schools, and prisons, is a subject of great practi- 

 cal importance. It is to be borne in mind that it is not sufficient for health 

 that a room should contain the quantity of air requisite for the support of 

 its inhabitants during a given time only, since after they have remained in 

 it but a part of that time, the amount of carbonic acid and other products 

 of disintegration which its atmosphere will contain will be large enough to 

 interfere greatly with the due aeration of their blood; but care ought to be 

 taken that the air is renewed so frequently that the amount of carbonic acid 

 gas does not exceed at most one part per 1000. A small room with several 

 people in it may be better ventilated than a larger one with few inhabitants, 

 if provisions for the renewal of the air in it are superior; and it is fortunate 

 that a considerable amount of fresh air is introduced into all houses of modern 

 construction by what may be termed spontaneous ventilation, as distinguished 

 from the special arrangements made by builders and architects. This spon- 

 taneous ventilation is effected through the crevices of the doors and windows, 

 especially when open fireplaces are used as in England, and Petteukofer 1 

 has shown that a large and hitherto unsuspected interchange of air takes 

 place even through the walls. Thus in one case where the room had brick 

 walls, and its size was 2650 cubic feet, with a difference of temperature of 

 34 F. (66 F. in, 32 outside), the contents of the room changed once in 

 one hour, a quantity of air equal to 2650 feet entering in that time. With 

 the same difference of temperature, but with a good fire in the stove, the 

 communication of which with the chimney was made as free as possible, the 

 change of the air rose to 3320 cub. feet, or about 25 per cent. When all 

 openings, crevices in windows and doors, were thoroughly pasted up, there 

 was still a change of 1060 feet per hour, or a fall of 28 per cent. With a 

 difference of temperature of 71 in, and 64 outside, the change amounted 

 to 780 cubic feet only per hour, and when a window of 8 feet square was 

 opened the change rose to 1060 feet per hour. These quantities are instruc- 

 tive : they show that a difference of temperature of 34 with carefully shut 

 openings and crevices, is of greater influence than large communications with 

 the outer air at a small difference of temperature, and that a large ward or 

 room with one fireplace is not necessarily well ventilated. Petteukofer 

 found that in one of his rooms when the difference of temperature between 

 the inside and outside was 9.5 F. the spontaneous ventilation through each 

 square yard of the wall amounted to about 7 cubic feet or 43 gallons per 

 hour. The material of which the wall is constructed of course exerts a great 

 influence on the spontaneous ventilation ; thus Marker and Schultze found 

 in their researches on the spontaneous ventilation of stables, that for one 

 square yard of free wall at 9.5 F. difference of temperature, the spontaneous 

 ventilation amounted per hour with walls of sandstone to 4.7 cub. feet, of 

 quarried limestone to 6.5, of brick to 7.9, of tufaceous limestone to 10.1, and 

 of mud to 14.4 cubic feet. The renewal of air should, if possible, be so 

 regulated that no draught or sensation of air in motion is experienced. The 

 observations of Pettenkofer and Voit made in their great apparatus at Mu- 

 nich show that no resistance or sense of coolness is felt at ordinary tempera- 

 ture if the hand be moved at a less rate than 19 inches per second, and that 

 as a rule the motion of the air is only felt distinctly when it amounts to 3i 

 feet per second. The velocity of the air as measured by the anemometer in 

 this climate, is about 10 feet per second, which would make about 7 miles 



1 See three Lectures, entitled The Air, in relation to Clothing, Dwelling, and Soil, 

 delivered before the Albert Society of Dresden, and translated by Aug. Hess, M.D., 

 1874. 



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