282 BACTERIOLOGY. 



environment. That is to say, its morphology is always 

 more regular, and it is smaller on glycerin-agar-agar 

 than on other media used for its cultivation ; while 

 upon Loffler's blood-serum the other extremes of devel- 

 opment appear ; here one sees, instead of the very short, 

 spindle, lancet, club-shaped, always segmented and 

 regularly staining forms as seen upon glycerin-agar, 

 long, irregularly staining threads, that are sometimes 

 clubbed and sometimes pointed at their extremities. 

 They are usually marked by areas that stain more 

 intensely than do the rest of the rod, and at times they 

 may be a little swollen a't the centre. These differences 

 are so conspicuous that microscopic preparations from 

 cultures from the same source upon glycerin-agar-agar 

 and upon blood-serum, when placed side by side, would 

 hardly be recognized as of the same organism, unless 

 its peculiar behavior under these circumstances was 

 already known. 



FlQ. 54. 



Bacillus diphiheriss, u. Its morphology when cultivated on glycerin-agar. 

 b. Its morphology as seen in cultures on LbJHer's blood-serum. 



On plain nutrient agar-agar (that is, nutrient agar- 

 agar without glycerin) ; on solidified egg-albumin ; on 

 a medium consisting of dried albumin, as found in 

 commerce, dissolved in bouillon (about 10 grammes 

 albumin to 100 c.c. of bouillon containing 1 per cent, 

 of grape-sugar) ; in bouillon without glycerin, and in 



