394 PATHOGENIC BACTERIA. 



the blood-serum-mixture tubes, without either again 

 touching the throat or being sterilized. The tubes thus 

 inoculated are stood away in an incubating oven at the 

 temperature of 37 C. for twelve hours, then examined. 

 If the diphtheria bacillus is present upon the first and 

 second tubes, there will be a smeary yellowish-white layer, 

 with outlying colonies on the second tube, while the third 

 tube will show rather large isolated whitish or slightly 

 yellowish colonies, smooth in appearance, but rather ir- 

 regular in outline. Very often the colonies are china- 

 white in appearance. These colonies, if found by micro- 

 scopic examination to be made up of diphtheria bacilli, 

 will confirm the diagnosis of diphtheria, and will at the 

 same time give pure cultures when transplanted. There 

 are very few other bacilli which grow so rapidly upon 

 Loffler's mixture, and scarcely one other which is found 

 in the throat. 



Ohlmacher recommends the microscopic examination 

 of the still invisible growth in five hours. A platinum 

 loop is rubbed over the inoculated surface ; the material 

 secured is then mixed with distilled water, dried on a 

 cover-glass, stained with methylene blue, and examined. 

 This method, if reliable, will be very valuable in making 

 an early diagnosis preparatory to the use of the antitoxin. 



The presence of diphtheria bacilli in material taken 

 from the throat does not necessarily prove the patient to 

 be diseased. Virulent bacilli can often be discovered in 

 the throats of healthy persons who have knowingly or 

 unknowingly come in contact with the disease. The 

 bacteriologic examination is only an adjunct to the 

 clinical diagnosis, and must never be taken as positive 

 in itself. 



The bacillus grows similarly upon blood-serum and 

 Loffler's mixture. Upon glycerin agar- agar and agar-agar 

 the colonies are much larger, more translucent, always 

 without the yellowish-white or china-white color of the 

 blood-serum cultures, and generally are distinctly divided 

 into a small elevated centre and a flatter surrounding zone 



