40 MEANS OF PREVENTION. 



of inhaled particles, or by personal contact, on the part of the 

 worker, with poisonous substances, or by the breathing of irritant 

 gases, or vapours, exhaled from them. In order to change the 

 character of an unhealthy, to a healthy occupation, it is only 

 necessary to free the air of its suspended matter, such as dust or 

 other foreign bodies. To accomplish this object, many contriv- 

 ances have been devised and tried ; but, as we shall see, without 

 their having conferred any substantial benefit. The steel-grinders 

 are provided with the magnetized wire-gauze respirator, which 

 was proved to effectually prevent access of steel-dust to the lungs. 

 Stone-cutters and millstone-grinders are likewise provided with a 

 respirator, which would equally well protect them ; while the flax- 

 workers of the north of Ireland are familiar with an instrument 

 known as the "Baker respirator," specially designed for their 

 benefit. 



The efficiency of an ingenious respirator, constructed to enable 

 the London Eire Brigade to inhale an atmosphere of dense smoke, 

 otherwise suffocating, was some years ago devised and successfully 

 tested by Professor Tyndal. It is made of cotton wool, moistened 

 with glycerine, and mixed with pieces of charcoal. 



Here is another instrument, a respirator, which I devised 

 some time ago for a different purpose ; it is more complex, but 

 the same in the principle of its construction as those I have 

 named to you ; its objects are to warm, medicate, and filter the air 

 in its passage to the pulmonary organs. From what I have said, 

 you will have perceived that there is really no practical difficulty 

 in depurating the air of its dust, and other hurtful foreign 

 matter, by means of mechanical adaptations such as I have 

 spoken of. The difficulty, as we shall afterwards see, is of 

 another kind. In my lecture on " Preventible Diseases " to the 

 Health Society, I took the opportunity, by means of an interest- 

 ing experiment, to show you the important fact that cotton- 

 wool held over the mouth and nostrils effectually frees the air of 

 its suspended particles. I have had this cotton-wool prepared so 

 as to remove its impurities, and at the same time enhance its 

 absorbing property. In virtue of these combined properties, 

 it is, not only an efficient dust filter, but also, by absorbing 



