38 



MICRO-ORGANISMS AND FERMENTATION. 



Miguel performed his first experiments with a so-called 

 aeroscope (Fig. 8), which is constructed in the following 

 manner. From the top of a bell. A, proceeds a tube, C, through 

 which air is aspirated, thus causing it to pass through the bell. 

 To the latter is screwed a hollow cone, the mouth, B, of which 

 points downwards ; in the apex, D, of this cone there is a 

 very fine opening through which the aspirated air is drawn, 

 and immediately over this opening is fixed a thin glass- 

 plate covered with a mixture of glycerine and glucose. The 

 particles carried in by the air settle to a great extent on 

 the viscous mixture. The micro-organisms here intercepted 

 are distributed as equally as possible on the glass-plate, 

 and counted under the microscope. This method is so 



FIG. 

 Aeroscope. 



far defective in that it gives no information on the most 

 important point, namely, which and how many of the inter- 

 cepted germs are actually capable of development. 



In order to determine the number of germs capable 

 of development, and also their nature, Miquel employs the 

 following apparatus (Fig. 9). The flask A has fused into it 

 a tube, K, tapering below and nearly reaching to the bottom ; 

 the upper end of this is fitted with a ground cap, H, provided 

 with a narrow filter-tube containing sterilised cotton-wool, 

 asbestos, or glass-wool, as. On one side of the flask is a 

 tube, Asp, which is constricted in the middle and is provided 

 with two cotton-wool plugs, w f and w. On the other side is 

 another glass tube, which is connected by rubber, fc, with the 

 tube B, which is drawn out to a point, and closed by fusing the 



