BACILLUS MEGATHERIUM. 321 



eight hours there is a strong, genuine odor of Emmenthaler cheese; 

 also this occurs upon sterilized casein, precipitated by rennet. There 

 is never any gas formed from sugar. 



Bacillus megatherium. (De Bary.) Vorles. iiber Bak., 

 ii. Aufl., 1887. 



(Plate 41.) 



Microscopic Appearance. Rods 1.6-5 /* long, 0.6- 

 0.8 fj. thick, the ends not rounded, often united in long 

 strings (41, x). These dimensions are a certain demon- 

 stration that the organism becomes smaller after prolonged 

 cultivation (forma depauperata); we obtained this culture 

 from the hygienic institute in Berlin in 1888. De Bary 

 represents the thickness at about 3 p. (Compare Bac. oxa- 

 laticus, p. 323. ) 



Motility. By means of many peritrichous flagella it is 

 rather slowly motile (41, xi). 



Staining properties and requirements as to nu- 

 trient media, etc., are the same as in the Bac. subtilis. 



Gelatin Plate. (a) Natural size: Like Bac. subtilis 

 (41, m). 



(&) Magnified fifty times. Deep: Grayish, transparent, 

 more opaque toward the center, finely to coarsely granu- 

 lar, as if beset over the entire surface with most minute 

 hairs (41, iv). If the colony lies upon the surface, the 

 periphery supports a row of rather long, very fine, deli- 

 cate hairs, while the middle zone is a little lighter. The 

 point at the middle remains compact (41, v) . It resembles 

 Bac. subtilis and Bac. mesentericus. 



Gelatin Stab. Tube- or sack-shaped liquefaction takes 

 place along the stab. The liquid is turbid; sometimes, 

 especially later, with cloudy flocculi. Later the lique- 

 faction becomes cylindric (41, i). 



Agar Plate. (a) Natural size: White to grayish-white, 

 a little elevated, moistly shining disks (41, vi). 



(6) Magnified fifty times : In the earliest stages the deep 

 colonies possess hairy or corkscrew-shaped outgrowths 

 (41, vn, i), while the superficial ones possess a delicate, 

 extremely transparent zone (41, vn, e). The latter in 

 time becomes opaque, coarsely crummy, yellowish-brown, 

 21 



