74 HEALTH AND DISEASE 



convey to the reader a fair idea of the influence which the opening of 

 doors and windows can be made to exercise upon the distribution of air 

 throughout a stable. The great value of these observations lies in the 

 fact that they refer to the very simple appliances which are at everyone's 

 command, consisting merely of ordinary doors and swing windows, placed 

 opposite to each other in walls not more than 30 feet apart. 



Writers on ventilation describe artificial ventilation as distinct from 

 the "natural" ventilation obtained by ordinary appliances such as doors, 

 windows, and holes in buildings. Artificial ventilation may be arranged to 

 operate in one of two ways, namely, (l) by "extraction" of the air which 

 is already in the building, and (2) by " propulsion ", which consists in the 

 driving out of contaminated air by the forcible introduction of fresh air. 

 Extraction is effected by heat, by steam-jet, or by fan or screw. The most 

 simple instance of " extraction " by heat is that of the common fireplace, 

 with its open chimney, in which the upward current is in proportion to the 

 amount of heat and the area of the chimney. 



Dr. Parkes refers to a room which he frequently examined where the 

 area of the chimney was 1'5 square foot. There was no down-draught, but 

 a constant upward current of 4 feet per second; the discharge per second 

 was then 6 cubic feet, or 21,600 cubic feet per hour. The capacity of the 

 room was 2000 cubic feet, so that a quantity equal to the total air in the 

 room passed up the chimney nearly eleven times per hour. Notwithstand- 

 ing this, the room became close when shut up with two or three persons. 

 The explanation given is, that when the windows were shut the fire was 

 chiefly fed with air which entered below the doors, and, flowing near the 

 ground to the chimney, was never properly diffused through the room. It 

 was found that the current near the ground moved from 1'6 foot to 2 '6 feet 

 per second, and chilled the feet. A few feet above the ground no move- 

 ment could be discovered. No better example than this could be given of 

 the great importance of arranging for the proper entrance and distribution 

 of air as well as for its exit, 



When a fire is lighted, all places in the room through which air can pass 

 act as inlets, and as the necessary result currents in various directions come 

 from places which were meant to be outlets, causing what are so very much 

 dreaded by people in general, so-called draughts. The common remedy for 

 this state of things is the blocking up of all the cracks in doors and 

 windows which can be reached, and the plugging of any ventilating tubes 

 or shafts by the aid of dusters or any other material at hand. In a stable 

 a mass of hay forms a convenient plug for any hole through which the air 

 passes too freely for the comfort of the persons employed about the stable. 

 In a room so treated, it is noticed that when all the openings through 



