” 
614 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
probably be desirable to keep the relative humidity between 60° and 
707. 
Another point which may be Mb yee in the leht of current 
opinion is the importance of “ perflation,” or the flushing out of a room 
at intervals, with vigorous drafts of fresh cool air. Where there are 
no air currents the hot, moist, vitiated air from the body clings round 
us like an “aerial blanket,” as Prof. Sedgwick calls it, and each of 
us is surrounded by a zone of concentrated discomfort. The delight- 
ful sensation of walking or riding against a wind is perhaps largely 
due to the dispersion of this foul envelope, and it is important that a 
fresh blast of air should sometimes blow over the body in order to 
produce a similar effect. The same process will scatter the odors 
which have been noted as unpleasant and to some persons poten- 
tially injurious. The principal value of the carbon-dioxide test 
to-day lies in the fact that under ordinary conditions high carbon 
dioxide indicates that there are no air currents changing the atmos- 
phere about the bodies of the occupants. 
There is one other problem of atmospheric pollution to which special 
reference should be made. The presence of noxious fumes, and 
still more the presence of fine morgani¢ or organic dust, in the air 
constitutes a grave menace to health in many processes and is an 
important contributory cause of tuberculosis. The normal body 
has its ‘fighting edge” and can protect itself against the tubercle 
bacillus if given a fair chance; but the lung tissue, which is lacerated 
by sharp particles of granite or steel quickly succumbs to the bac- 
terial invader. In dusty trades, like stone cutting and cutlery 
working and émery grinding, 75 per cent of all deaths among the 
operatives are often due to tuberculosis, against 25 per cent for the 
normal adult population. This may be fairly interpreted as mean- 
ing that the actual death rate from tuberculosis in these trades is 
from two to four times as high as in a corresponding average popu- 
lation. In other words, three or four or five out of a thousand of 
these workers are sacrificed every year to the conditions under which 
they labor. The elimination of the dust by special hoods and fans 
is imperative in such industries and must be supplemented in extreme 
cases by the compulsory use of respirators. 
It is extraordinary how little is known to-day of the setae condi- 
tions of factory air, either by manufacturers or by sanitarians. So 
far as | am aware ie New York department of labor is the only 
State department dealing with factory inspection which collects 
and publishes exact data in regard to the quality of the atmosphere 
in the workshops. If-the conditions indicated in these reports by 
Dr. C. 'T. Graham Rogers are typical, and there is no reason to doubt 
that they are, for the smaller industries at least, there is urgent need 
for betterment. The table below shows that of 215 workrooms 
inspected 156, or 73 per cent, had a temperature of over 72° and 63, 
