100 THE ACUTE SELF-LIMITED INFECTIONS 



For diagnosis of diphtheria use is made of direct examina- 

 tion of stained smears from the site of trouble, and cultures 

 upon blood serum, the best culture medium. 



The bacilli are rather characteristic in their irregular shape. 

 They are rods of unequal length and width, full of granules, 

 which stain more deeply than the rest of the rod. Their 

 ends are usually clubbed or the whole rod may have the 

 shape of a wedge. They may be straight or bent. They vary 



A. 



FIG. 32. Bacterium diphtherias: A, its morphology on glycerin-agar- 

 agar; R, its morphology on Loffler's blood serum; C, its morphology on acid- 

 blood serum mixture. (Abbott.) 



from :TOTO "o to 21^07 of an inch in length and from STFWIF to 

 2T i"0"o f an inch in breadth. They are very apt to show pecu- 

 liar, more or less characteristic forms of degeneration. A 

 special stain called Loffler's alkaline methylene-blue solution 

 is used to show the peculiarities of their structure. The 

 diphtheria bacilli are non-motile, non- spore-bearing rods. 

 They are not pronounced in their manifestations of life under 

 artificial conditions, except for toxin production, but they 



