DIFFERENT PARTS OF THE MICROSCOPE. 171 



as its growth in media of different reactions, are to be 

 studied. The property of producing fermentation with 

 the liberation of gases, and the character and quantita- 

 tive relations of these gases must be ascertained ; if it 

 produces pigment, what are the conditions favorable and 

 unfavorable to this function ; and, lastly, we must con- 

 sider its behavior when introduced into the bodies of 

 animals used for experimental work i. e., is it a dis- 

 ease-producing organism, or does it belong to the group 

 of innocent saprophytes? 



We have learned the methods of obtaining colonies, 

 and have acquainted ourselves with some of the pecu- 

 liarities by which they are distinguished from one an- 

 other. The next important step is to determine the 

 morphology of the individuals composing these colonies 

 as well as their relation to each other in the colony. 

 These points are decided by microscopic examination 

 of bits of the colony which are transferred to thin glass 

 cover-slips, upon which they are dried, stained, and 

 mounted. Cover-slips for this purpose are prepared in 

 two ways : either by taking up a bit of the colony on a 

 platinum needle, smearing it upon a cover-slip, staining 

 it, and examining it by which only the morphology of 

 the individual bacteria can be made out or by the method 

 of u impression cover-slip preparations," by which not 

 only the morphology, but also the relation of the organ- 

 isms to one another in the colony can be determined. The 

 details of these methods will be found in the chapter on 

 the method of staining. 



MICROSCOPIC EXAMINATION OF PREPARATIONS. 



THE DIFFERENT PARTS OF THE MICROSCOPE. 

 Before describing the process of examining preparations 



