110 THE ACUTE SELF-LIMITED INFECTIONS 



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 from inrij o~ to Y oVo 

 of an inch in length, and from ^Triuiy to YTFUIF f an 

 inch in breadth. They are very apt to show peculiar, 

 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 grow readily 

 on most laboratory culture media. Solidified blood 

 serum is the preferred artificial foodstuff. Upon it they 

 grow in such a manner as to render diagnosis easy, 

 both by the naked-eye appearance and by their shapes 

 under the microscope. These bacilli grow best at the 

 body temperature, 37 C. or 98 F., but also at a 

 lower point. 



They are killed at 58 C. or 140 F. for ten minutes. 

 Boiling kills in one minute. In the dry state, protected 

 from daylight, these organisms may live several months. 

 With such protection, when moist or in exudate, as 

 from the throat, life may persist for at least four 

 months. Direct sunlight kills within half an hour. 

 On cloth or other absorbing material their life is long, 

 but indeterminate. On coins thev die in twelve to 



