328 -B^ OTEBIOL OGY. 



especially characteristic to find irregular, bizarre forms, 

 such as rods with one or both ends swollen, and very 

 frequently rods broken at irregular intervals into short, 

 sharply marked segments, either round, oval, or with 

 straight sides. Some forms stain uniformly, others in 

 various irregular ways, the most common being the 

 appearance of deeply stained granules in a lightly 

 stained bacillus. 



By a series of studies upon this organism when cul- 

 tivated under artificial conditions we have found that 

 its form depends very largely upon the nature of its 

 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 Loeffler's blood-serum the other extremes of de- 

 velopment appear: here one sees, instead of the very 

 short, spindle, lancet, club-shaped, always segmented 

 and regularly staining forms as seen upon glycerin-agar- 

 agar, long, irregularly staining threads that are some- 

 times clubbed and sometimes pointed at their extremi- 

 ties. They are usually marked by areas that stain more 

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

 may be a little swollen at the centre. These differences 

 are so conspicuous that microscopic preparations from 

 cultures from the same source, but cultivated in the one 

 case on glycerin-agar-agar and in the other upon blood- 

 serum, when placed side by side would hardly be recog- 

 nized as of the same organism, unless its peculiar be- 

 havior under these circumstances was already known. 

 During the past year or so various authors have called 

 attention to branching forms of this organism that are 

 occasionally encountered, especially when cultivated 

 upon albumin. We have never seen the branching 



