132 RESPIRATION 



This draws an equivalent volume of air, moist and cool, through the 

 cracks about the doors and windows, if not from a supply provided by 

 some system of ventilating apparatus. 



Perhaps the next best form of heating, so far as ventilation is concerned, 

 is the hot-air furnace. When properly built and run, it provides a cur- 

 rent of fresh air from out of doors warmed and humid enough to be 

 breathed. Steam and hot water have so great mechanical advantages 

 that their use is becoming very widespread. Neither of these methods, 

 however, provides any ventilation nor any mode of moistening the air. 

 The heating-stove has these disadvantages in an exaggerated form because 

 of the extreme temperatures they often reach, while the small basin of 

 water sometimes attached to the stove above, intended to moisten the 

 air, is almost ludicrously inadequate. Whatever the mode of heating, 

 the matter of direct ventilation by means of open windows will seem to 

 the next generation a very simple matter, and children now being born 

 will look back, we may imagine, with mild amazement on the fear many 

 of their parents and grandparents now have of a current of air. Edu- 

 cation is advancing rapidly in this important regard, and it is a common 

 experience that toleration even of cold draughts may be readily acquired 

 without any sort of harm and with great benefit to everyone; and with 

 life itself to the millions of every century who else would die of tuber- 

 culosis of the lungs. 



Diffusion also assists ventilation everywhere to no small extent, quickly 

 evening up the composition of the air in an open space. Difference in tem- 

 perature and consequent density of air is another cause of the air's 

 movement. A fair allowance of air space in the large cities is 1500 cubic 

 feet, and 4500 cubic feet of air hourly per capita. The floor-space should 

 be one-tenth of the cubic space. 



A method of public school-room ventilation especially that commends 

 itself on many accounts is the free opening of the windows for live 

 minutes every half -hour, the pupils meanwhile marching about the 

 room. This would keep the air pure at a low monetary cost. It would 

 relieve the brain of its congestion by vaso-motor rearrangement of the 

 blood, and it would accustom the child to small changes in the temper- 

 ature of the air. Under such a system, harmful over-strain of the mind, 

 eyes, etc., would be much rarer than now, and the supply of respiratory 

 oxygen greatly increased. 



Save in the hospitals, the problem of ventilation certainly will be a 

 simpler one continually as more and more of the mass of the people 

 hear and believe the gospel of fresh air as taught them in the schools 

 that oxygen is as food and drink and, unlike them, free; and to take it 

 in great abundance day and night is to ward off multiform disease and 

 to add to the length and happiness of their lives. 



