614 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1911. 



probably be desirable to keep the relative humidity between 60° and 

 70°. 



Another point which may be emphasized in the light 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 ah- 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 ah' 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 inorganic 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 emery 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 } r ear 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 actual condi- 

 tions of factory air, either by manufacturers or by sanitarians. So 

 far as I am aware the 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, 



