212 BACTERIOLOGY 



continuous observation. The form of chamber best adapted 

 to the purpose is one which envelops the whole microscope. 

 It is provided with a window through which the light enters, 

 and an arrangement by which the slide may be moved from 

 the outside. The formation of spores requires a much 

 longer time than the germination of spores into bacilli, but 

 with patience both processes may be satisfactorily observed. 



It will be noticed that the description of this process is 

 very much like that which immediately precedes, but differs 

 from it in one respect, viz., that in this manipulation we 

 are not making a preparation which is simply to be ex- 

 amined and then thrown aside, but it is an actual pure 

 culture, and must be kept as such, otherwise the observa- 

 tion will be worthless. For this reason the greatest care 

 must be observed in the sterilization of all objects employed. 

 Studies upon spore formation by this method frequently 

 continue over hours, and sometimes days, and contamina- 

 tion must, therefore, be carefully guarded against. The 

 study should be begun with the vegetative form of the 

 organisms; the hanging-drop preparation should, for this 

 reason, always be made from a perfectly fresh culture of 

 the organism under consideration before time has elapsed 

 for spores to form. 



The simple detection of the presence or absence of spore 

 formation can in many cases be made by other methods. 

 For example, many species of bacteria which possess this 

 property form spores most readily upon media from which 

 it is somewhat difficult for them to obtain the necessary 

 nourishment; potatoes and agar-agar that have become 

 a little dry offer very favorable conditions, because of the 

 limited area from which the growing bacteria can draw their 

 nutritive supplies, and because of the free access which they 



