l82 BACTERIOLOGICAL DIAGNOSIS. 



The colonies of the pneumococcus are small flat white 

 points which do not tend to fuse together. They are 

 difficult to see when they are young, and in case of 

 doubt the tube should be returned to the incubator. 



The colonies of the typhoid bacillus and the bacillus coli 

 are whitish and opalescent. They usually have an 

 angular or polygonal appearance when small, and tend 

 to run together when older if they are thickly set. 

 Their discrimination must be left to an expert. 



The bacillus of plague forms white colonies which are 

 circular or have a crenated outline ; they tend to run 

 together and form a uniform film over the surface of the 

 medium. 



The gonococcus, if it develops, forms very minute 

 transparent colonies which have been compared to 

 droplets of dew. They do not become confluent. 

 This organism will not grow if transplanted on to 

 the surface of ordinary media unless a thick film of 

 blood be previously spread over it. 



After cultures have been obtained they are to be 

 examined microscopically by the method described on 

 page 29, and the morphological appearances compared 

 with those of the pathogenic organisms which we have 

 enumerated. It is especially important to test whether 

 the organism which has been isolated, stains by Gram's 

 method or not. 



SECTION CUTTING. 



The methods employed in section cutting are some- 

 what outside the scope of this work, inasmuch as' 

 sections are rarely necessary for the purposes of bacterio- 



