92 SOLID CULTIVATION MEDIA. 



the tube proceeding from the cylinder. The clamp and cap of cotton 

 wool are removed, and the litre flask more distant from the cylinder 

 is allowed to empty itself by siphon action, drop by drop. Water is 

 thus drawn out of the nearer flask to supply the place of that removed 

 from the other, and air is drawn from the cylinder to take the place • 

 of the water. Thus a current sets in from the outer air, through the 

 fine pore, into the cylinder, carrying with it representatives of the 

 germs in the atmosphere tested. A litre of outside air will have been 

 drawn slowly into the cylinder, by the time the litre flask is quite 

 empty, and then the experiment is stopped by clamping the tube and 

 replacing the cap over the pore in the indiarubber sheeting. The 

 germs, which enter by the pore, rapidly gravitate into the layer of 

 gelatine on the floor of the cylinder, and the number of foci of growth 

 which appear in the jelly a few days after exposure corresponds to the 

 number of germs per litre in the atmosphere tested. 1 



(C.) Examination of Water for Micro-Organisms. 



46. This examination is now looked upon as a matter of considerable 

 importance, and in this country and in Germany various methods have 

 been suggested for making it as complete and as accurate as possible. 



Where any sediment can be obtained from the water, after allowing 

 it to stand for some time, it is a comparatively easy matter to 

 examine with the microscope the organisms which are deposited 

 along with the solid particles. Without further amplification, how- 

 ever, such an examination is always far from satisfactory, and affords 



1 Dr. Maddox very ingeniously caused currents of air to impinge on a glass 

 slide smeared with pure glycerine. The glycerine was then examined microscopi- 

 cally. With this glycerine inoculations may be made into various media, in 

 order that the organisms collected may be more thoroughly studied. Dr. Arthur 

 Ransome examined the breath of persons affected with phthisis for tubercle bacilli, 

 by collecting the breath in a glass globe, and condensing the aqueous vapour con- 

 tained in this breath, by surrounding the globe with a mixture of ice and salt. 

 The condensing vapour, " it was found, carried down all the organic matter con- 

 tained in the breath," and micio-organisms could be examined in this condensed 

 aqueous vapour. 



In order to distinguish the tubercle bacilli, he mixed a small quantity of white 

 of egg with the water so obtained, and then treated the mixture as if it were or- 

 dinary sputum, staining by Heneage Globes' method. This method may be 

 employed with advantage wherever the air contains a large percentage of moisture. 



