

VENTILATION OF ROOMS. 201 



so that the C0 2 does not exceed '06 per cent. , 3000 cubic feet of air per hour must be supplied, 

 i.e., the air in the space must be renewed three times per hour.] 



[Floor-Space. It is equally important to secure sufficient floor-space, and this is especially 

 the case in hospitals. If possible, 100-120 square feet of floor-space ought to be provided for 

 each patient in a hospital-ward, and if it is obtainable a cubic space of 1500 cubic feet (Parkes). 

 In all cases the minimum floor-space should not be less than T \ of the cubic space.] 



Overcrowding. When there is overcrowding in a room, the amount of C0 2 increases. V. 

 Pettenkofer found the normal amount of C0 2 ( '04 to "05 per 1000) increased in comfortable 

 rooms to 0'54-0*7 per 1000; in badly ventilated sick chambers = 2 , 4 ; in overcrowded audi- 

 toriums, 3*2 ; in pits = 4 '9 ; in schoolrooms, 7 "2 per 1000. Although it is not the quantity of 

 C0 2 which makes the air of an overcrowded room injurious, but the excretions from the outer 

 and inner surfaces of the body, which give a distinct odour to the air, quite recognisable by the 

 sense of smell, still the amount of C0 2 is taken as an index of the presence and amount of these 

 other deleterious substances. "Whether or not the ventilation of a room or ward occupied by 

 persons is sufficient, is ascertained by estimating the amount of C0 2 . A room which does not 

 give a disagreeable, somewhat stuffy, odour has less than 0'7 per 1000 of C0 2 , while the ventila- 

 tion is certainly insufficient if the C0 2 = 1 per 1000. As the air contains only 0*0005 cubic 

 metre C0 2 in 1 cubic metre of air, and as an adult produces hourly "0226 cubic metres C0 2 , 

 calculation shows that every person requires 113 cubic metres of fresh air per hour, if the C0 2 

 is not to exceed 0*7 per 1000 : for 0*7 : 1000 = (0 '0226 + xx 0'0005): x t i.e., x -113. 



[Vitiating Products. In a state of repose, an adult man gives off from 12 to 16 cubic feet of 

 C0 2 in twenty-four hours, or on an average "6 cubic feet per hour. To this must be added a 

 certain quantity of organic matter, which is extremely deleterious to health. "While the C0 2 

 diffuses readily and is easily disposed of by opening the windows, this is not the case with the 

 organic matter, which adheres to clothing, curtains, and furniture ; hence to get rid of it, a 

 room, and especially a sleeping apartment, requires to be well aired for a long time, together 

 with the free admission of sunlight. We must also remember that an adult gives off from 25 to 

 40 oz. of water by the skin and lungs. The nature of the organic matters is not precisely 

 known, but some of it is particulate, consisting of epithelium, fatty matters, and organic 

 vapours from the lungs and mouth. It blackens sulphuric acid, and decolourises a weak solu- 

 tion of potassic permanganate. As a test, if we expire through distilled water, and this water 

 be set aside for some time in a warm place, it will soon become foetid. We must also take into 

 consideration the products of combustion ; thus 1 cubic foot of coal-gas, when burned, destroys 

 -all the O in 8 cubic feet of air {Parkes).'] 



Methods. In ordinary rooms, where every person is allowed the necessary cubic space (1000 

 cubic feet), the air is sufficiently renewed by means of the pores in the walls of the room, by the 

 opening and shutting of doors, and by the fireplace, provided the damper is kept open. It is 

 most important to notice that the natural ventilation be not interfered with by dampness of the 

 walls, for this influences the pores very greatly. At the same time, damp walls are injurious to 

 health by conducting away heat, and in them the germs of infectious diseases may develop. 



[Natural Ventilation. By this term is meant the ventilation brought about by the ordinary 

 forces acting in nature ; such as diffusion of gases, the action of winds, and the movements 

 excited owing to the different densities of air at unequal temperatures.] 



[Artificial Ventilation. Various methods are in use for ventilating public buildings and 

 dwelling-houses. Two principles are adopted for the former, viz., extraction and propulsion of 

 air. In the former method, the air is sucked out of the rooms by a fan or other apparatus, while 

 in the latter, air is forced into the rooms, the air being previously heated to the necessary 

 temperature.] 



[A very convenient method of introducing air into a room is by means of Tobin's tubes, 

 placed in the walls. The air enters through these tubes from the outside near the floor, and is 

 ^carried up six or more feet, to an opening in the wall ; the cool air thus descends slowly. For 

 -a sitting-room, a convenient plan of window ventilation is H. Bird's Method : Raise the 

 lower sash and place under it, so as to fill up the opening, a piece of wood 3 or 4 inches high. 

 Air will then pass in, in an upward direction, between the upper part of the lower sash-frame 

 and the lower part of the upper one.] 



138. FORMATION OF MUCUS, SPUTUM. The respiratory mucous mem- 

 brane is covered normally with a thin layer of mucus (fig. 130, a). It so far inhibits 

 the formation of new mucus by protecting the mucous glands from the action of 

 cold or other irritative agents. New mucus is secreted as that already formed is 

 removed. An increased secretion accompanies congestion of the respiratory mucous 

 membrane [or any local irritation]. Division of the nerves on one side of the 

 trachea (cat) causes redness of the tracheal mucous membrane and increased secre- 

 tion (Rossbach), [but the two processes do not stand in the relation of cause and 

 effect]. The secretion cannot be excited by stimulating the nerves going to the 



