280 BACTERIOLOGY. 



its isolation by this method a matter of but little diffi- 

 culty. 



After twenty-four hours in the incubator the tubes 

 will present a characteristic appearance. Their surfaces 

 will be marked at different points by more or less 

 irregular patches of a white or cream-colored growth 

 which is usually more dense at the centre than at its 

 irregular periphery. 



Except now and then, when a few orange-colored 

 colonies may be seen, these large irregular patches are 

 the most conspicuous objects on the surface of the 

 serum. Occasionally, almost nothing else appears. 



The cover-slips made from the membrane at the 

 time the cultures were prepared will be found on micro- 

 scopic examination to present, in mjiny cases, a great 

 variety of organisms, but conspicuous among them 

 will be noticed slightly curved bacilli of irregular size 

 and outline. In some cases they will be more or less 

 clubbed at one or both ends ; sometimes they appear 

 spindle in shape, again as curved wedges ; now and then 

 they will be seen irregularly segmented. They are rarely 

 or never regular in outline. If the preparation has 

 been stained with Loffler's alkaline methylene-blue 

 solution many of these irregular rods are seen to be 

 marked by circumscribed points in their protoplasm 

 which stain very intensely ; they appear almost black. 

 This irregularity in outline is the morphological char- 

 acteristic of the bacillus diphtherice of Loffiler. It must 

 be remembered, however, that the diagnosis of diphtheria 

 cannot be made from the examination of cover-slip 

 preparations alone, for there are other organisms present 

 in the mouth cavity, particularly in the mouth of persons 

 having decayed teeth, the morphology of which is so 



