3i) 245 



> * 



finally, towards the end of the expiration, the beam is, 

 as it were, pierced by an intensely black hole, in which 

 no particles whatever can be discerned. The air, in 

 fact, has so lodged its dirt within the lungs as to render 

 the last portions of the expired breath absolutely free 

 from suspended matter. This experiment may be re- 

 peated any number of times with the same result. It 

 renders the distribution of the dirt within the lungs as 

 manifest as if the chest were transparent. 



I now empty my lungs as perfectly as possible, and 

 placing a handful of cotton wool against my mouth and 

 nostrils, inhale through it. There is no difficulty in 

 thus filling the lungs with air. On expiring this air 

 through the glass tube, its freedom from floating matter 

 is at once manifest. From the very beginning of the 

 act of expiration the beam is pierced by a black aper- 

 ture. The first puff from the lungs abolishes the illumi- 

 nated dust and puts a patch of darkness in its place, 

 and the darkness continues throughout the entire course 

 of the expiration. When the tube is placed below the 

 beam and moved to and fro, the same smoke-like ap- 

 pearance as that obtained with a flame is observed. In 

 short, the cotton wool, when used in sufficient quantity, 

 completely intercepts the floating matter on its way to 

 the lungs. 



And here we have revealed to us the true philosophy 

 of a practice followed by medical men, more from in- 

 stinct than from actual knowledge. In a contagious at- 

 mosphere the physician places a handkerchief to his 

 mouth and inhales through it. In doing so he uncon- 

 ciously holds back the dirt and germs of the air. If the 

 poison were a gas it would not be thus intercepted. 

 On showing this experiment with the cotton wool to Dr, 



