IMPORTANCE OF VARIABILITY 103 



ordinary fashion. Yet their record is far better than that of 

 group III, — the warmer rooms with the most approved system 

 of fan ventilation. It should be noted here that no attention was 

 paid to the dress of the children. That is, in selecting rooms for 

 the different types of ventilation, the dress and social or physical 

 condition of the children played no part. In all three groups of 

 rooms the children were simply the ordinary type found in the 

 average sections of New York. This facts lends added importance 

 to the contrast between groups II and III. In both of these 

 the temperature averaged the same, approximately 68**. The only 

 difference was in the system of ventilation. In both groups the 

 air was perfectly fresh. In one case, however, it came in through 

 the windows. During the first year no attempt was made even 

 to prevent drafts, but in the second year boards were placed at 

 the bases of the windows so that the air did not blow directly on 

 the children. Yet in both years this kind of ventilation proved 

 much better than the other. In the rooms of group III fresh air 

 was taken from outside just as in group II, but instead of enter- 

 ing the rooms directly it was heated and then blown in by means 

 of fans. In fact, the system of ventilation was what is commonly 

 supposed to be ideal, — no drafts, no sudden changes, no chance 

 for the air to stagnate. Yet there were 30 per cent more absences 

 from respiratory diseases than in the rooms with window ventila- 

 tion, and over twice as many of the children in attendance had 

 colds or similar ailments. This striking difference cannot have 

 been due to the quality of the air, to its mean temperature, or to 

 its humidity. It must apparently have been due to its variability. 

 We try to keep our winter temperature as uniform as possible. 

 In so doing we commit a great folly. What we want is not uni- 

 formity, but variability. If we could live all the time in air with 

 the right variability as well as the right temperature and humid- 

 ity, who knows what we might accomplish.? Our bodies, our judg- 

 ment, and our wills would all be stronger than now. Our death- 

 rate would diminish, and our happiness be correspondingly in- 



