284 J. S. LAWRENCE AND W. W. FORD 



tures sent us which we do not regard as entitled to specific 

 rank, namely 



BaciVus pumilus Gottheil. 



Bacillus graveolens Gottheil. 



Bacillus tumescens Zopf. 



\/ 



Bacillus cereus Frankland 1887 



This organism was first described by the Franklands in 1887 

 (Franklands, 1887). It has since been described under a host of 

 names and it is impossible to say how many different species 

 are identical with it. It fs the most widely distributed organism 

 of this group in Baltimore, being found abundantly in milk, 

 soil, dust, water, and in the intestinal contents. It is partic- 

 ularly common as a laboratory contamination. The present 

 description applies to cultures received from the Krai collection, 

 from the American Museum, and from a number of American 

 laboratories and to over a hundred of our own isolations. 



Morphology. Regular bacilli with homogeneous protoplasm 

 and rounded ends, in young cultures measuring about 0.75 by 

 2.25 to 4 microns. Many of the organisms show peculiar re- 

 fractile bodies of various sizes as the cultures get older, presenting 

 a characteristic appearance. The nature of these bodies is 

 not clear as they do not give reactions for starch or volutin. 

 They can usually be differentiated from the beginning spores. 

 On glucose agar the bacilli are thicker and longer measuring 

 0.75 to 1 by 3 to 6 microns. Here the entire protoplasm of the 

 organism is converted into the bodies mentioned above. They 

 are globular, highly refractile, and are often as thick as the 

 organism. (Figures 25, 26 and 27.) 



Motility. Actively motile in young cultures. 



Staining properties. Gram-positive. 



Spore-formation. Spores are formed early on both plain and 

 glucose agar, often appearing within 24 hours or even in less 

 time. They may be central in position, excentric or even sub- 

 terminal but the latter location of the spore is rare. The spores 

 are usually wider than the organisms from which they spring 



