BACTERIUM DIPHTHERIA 455 



makes its isolation by this method a matter of but little 

 difficulty. 



After twenty-four hours in the incubator the tubes present 

 a characteristic appearance. Their surfaces are marked by 

 more or less irregular patches of a white or cream-colored 

 growth, which is usually more dense at the centre than at 

 the periphery. Except now and then, when a few orange- 

 colored colonies may be seen, these large irregular patches 

 are more 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 microscopic examina- 

 tion to present, in many 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 are 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 characteristic of bacillus diphtherise of 

 Loffler. 



It must be remembered, however, that the diagnosis 

 of diphtheria should not under all circumstances be made 

 from the examination of cover-slip preparations alone, espe- 

 cially when they are stained only by the usual method 

 i. e., with Loffler's methylene-blue. There are other organ- 

 isms present in the mouth-cavity, particularly in the mouths 

 of persons having decayed teeth, the morphology of which 



