CULTIVATION OF THE BACILLUS. 



93). They are at first 

 fairly uniform in size 

 and shape, but if a 

 culture is examined 

 from day to day it will 

 be found that their 

 appearance gradually 

 becomes irregular. 

 Many become swollen 

 at their ends into club- 

 shaped masses which 

 are stained deeply, 

 and the protoplasm 

 becomes broken up 

 into globules with 

 unstained parts be- 

 tween (Fig. 94). Some 

 become thicker 

 throughout, and seg- 



FIG. 93. Diphtheria bacilli of larger size 

 than in previous figure, showing also irregular 

 staining of protoplasm. From a three days' 

 agar culture. 



Stained with weak carbol-fuchsin. x 1000. 



mented so 

 pear like 



as 



FIG. 94. Involution forms of the diph- 

 theria bacillus ; from an agar culture of seven 

 days' growth. 



Stained with carbol-thionin-blue. x 1000. 



to ap- 

 large cocci, 

 and others show 

 globules at their ends, 

 the rest of the rod 

 appearing as a faintly- 

 stained line. These 

 are to be regarded as 

 involution forms, and 

 they occur more 

 quickly and abundant- 

 ly on the media less 

 suitable for their 

 growth, e.g., more 

 quickly on glycerine 

 agar than on serum. 

 The bacilli are non- 

 motile, and do not 

 form spores. 



