BACTERIOLOGY. 171 



the parts to be inoculated; then take an eye of the 

 growth on a needle after having made the incision at 

 the root of the tail of the animal ; inoculate the animal 

 and keep him in a cage to prevent him from spreading 

 the disease, if it is pathogenic. There are other meth- 

 ods. Fill a sterile hypodermic and inoculate the animal 

 in the dorsal veins of the ear and observe the same pre- 

 cautions as in other cases. This determines the 

 pathogen etic or non-pathogenetic properties of the bac- 

 teria. 



Staining bacteria is a very important step in the 

 study of bacteria. We will take that up when we 

 come to stain the several kinds of bacteria. 



Diagnosing bacteria is very difficult and is not free 

 from error. But we do it this way: we observe the 

 color or growth of the medium on which they grow 

 best. Their action in the hanging-drop preparation, 

 their morphology, their mode of bunching, their 

 source, their relation to air, their chemical production, 

 their action on an animal (pathogenetic property), their 

 reaction with Gram's stain and analine dyes. 

 These are the points by which we make a diagnosis of 

 a colony of bacteria. A few others we will discuss as 

 we come to them. 



COVSR-GLASS PREPARATIONS. 



These are simple to make, but we must be careful 

 not to contaminate the growth when we take the eye 



