DUST

isa = cause of disease. All the dusty trades have a high death rate, especially from consumption and other diseases of the lang. Street dust is composed largely of dried horse-dung, and this settling on milk is one of the chief causes of the epidemic diarrhea, so fatal to infants every summer. In the workshops the dust is largely determined by the nature of the trade, and the more gritty the nature of the dust the worse, hence knife-grinding and atone-dre ing are particularly deadly. In the country tho — of the gra cs every spring forms considerable tion of the total dust, and it is the irritation of this pollen which is the cause of yr rages It is to be noted that the nose is the natural filter a dust, and breathing through the mouth is thus thy. But even when breathing through the nose is habitual, the lungs of the town-dweller receive sufficient smoke and other forms of dust to change them from pink to blackish grey in the course of a lifetime. The microscope shows this discolouration to be due solely to particles of dust deposited in peplang substance. It is much to be desired that each house shoul consume its own smoke, and that the motor car should be the means of reducing the amount of horse-dung on our streets, in the near future. [s. 357]