BACTERIA 



some little skill to accomplish satisfactorily. When 

 our slide is prepared, with a magnification of at 

 least one thousand diameters, we may reasonably 

 hope that our trouble will be rewarded. 



At first we shall probably see nothing. We recall 

 that we had some difficulty in examining starch 

 grains, on account of the fact that they were colour- 

 less. This time we are dealing with a far more 

 difficult subject. When our eyes become accus- 

 tomed to the light, however, we shall be conscious 

 that there is something moving in our drop of water. 

 The Hay Bacillus is one of the moving forms, each 

 individual is furnished with a number of little whips 

 whose lashings enable it to travel through the water. 

 The whips cannot be seen in unstained bacilli; 

 experience, however, tells us that they are there, 

 for all these lowly plants which show movement are 

 seen when stained, to possess the little whips. The 

 process of staining kills the plants so that we cannot 

 see the little whips in action. 



Having detected that movement is taking place, 

 a little adjustment of focus and a further search 

 will reveal the bacilli to us, as little rod-like, colour- 

 less individuals. We shall see their cell contents if 

 they are sufficiently highly magnified and also their 

 cell walls. We may even observe them splitting, 

 each one into two individuals. We must keep our 

 sample of water for later examination. In fact, we 

 may examine drops from day to day, in exactly 

 the same manner. After a short lapse of time we 

 shall notice that the bacteria have increased to an 



161 L 



