SÉANCE DU 16 NQTEMBRE 997 



Coloration. 



Tbe diplitheric baeillus is coloured by the Gram melhod; this colo- 

 ration shouM always be used. 



If weak stains are used the diphtheric baeillus is deeply colored in 

 certain points. Thèse points are situated at the extremities, sometimes 

 in the center; the microbe around thèse corpuscles is badly colared. 

 Thèse granulations may be brought out by certain means of coloration. 

 Pustules always exist in the diphtheric baeillus ; they are missing or 

 are unipolar in the non-diphtheric. The détection of granulation has 

 made easier the différenciation of the microbe , but this can be 

 established hy a more reliable technique. 



The diphtheric baeillus stained by the Gram method looses its purple 

 coloration under the prolonged action of acétone alcohol at 1/20, also 

 looses its color if the slide is kept 15 minutes in absolute alcohol. The 

 non-diphtheric bacilli are coloured by the Gram stain and remain so 

 it the action of the acétone alcohol or the absolute alcohol is 

 prolonged. (This is . true only for cultures on sérum from 24 to 

 48 hours old.) A simple examination of the colonies and the coloration 

 of the bacilli altow the différenciation between thèse diphtheric bacilli 

 and other micro-organisms. 



Hâve we any right to consider thèse microbes as a part from the 

 group of diphtheric bacilli ? 



It is only by starting from absolutely pure cultures that it is possible 

 to show that the diphtheric baeillus can be separated from the others ; 

 the true diphtheric baeillus has characters which are not to be seen in 

 other microbes growing on coagulated sérum in from 24 to 48 hours 

 and stained by the Gram methad. 



Culture on deep glusosed, tubnsoled gélose-. 



In this médium the diphtheric baeillus grows on the whole length of 

 the tube, it does not vegetate oh the surface, it attacks the glucose and 

 produces acid which makes the litmus tincture turn red. 



On the other hand the greater number of bacilli known as pseudo- 

 diphtheric do no grow in depth and give on the surface of the tube a 

 culture which has the aspect of a creamy coating, thèse bacilli do not 

 attack the glucose and produce no acid, and moreover they alcalinize 

 the médium which becomes bluer than the média used for testing. 



Hère is however to our knowledge one exception : the Baeillus autis 

 communis grows in depth and attacks the glucose although more 

 slightly; therefore, it resembles more the diphtheric baeillus whereas 

 the other are absolutely différent. 



