KEY TO GENUS BACILLUS. 305 



(A) Stab culture in gelatin with projecting branches ; 



1. Branches distinct, usually only in the upper part of the stab. 

 Agar plate colonies, when magnified 60 times, have beautiful regular 

 curls. Agar streak culture without branches, wide, white with "sil- 

 very vesicles." Never motile. Pathogenic for animals. Bac. an- 

 thracis Cohn and Koch (p. 307). 



2. Branches delicate, extending along the entire length of the stab. 

 When magnified 60 times, the colonies in the agar plate exhibit irreg- 

 ular outgrowths in the form of roots or the mycelium of molds. Agar 

 streak culture has long, delicate, parallel transverse branches. Slug- 

 gishly motile. Not pathogenic tor animals. Bac. mycoides Flugge 

 (p. 316). 



(B) Stab culture in gelatin without projecting branches; motility de- 

 pendent upon peritrichotts flagella ; 



1. Potato growth at first moist and flat, later (about eight days) 

 with a distinctly mealy sprinkling. Bac. subtilis Cohn (p. 317). 



2. Potato growth moderately elevated, not characteristic, resem- 

 bling Bact. coli. Bac. oxalaticus Zopf, butyricus Hiippe, mega- 

 therium De Bary (pp. 321, 322, and 323). 



3. Potato culture hixuriant, moist, intensely yellow. Agar moist, 

 mustard yellow. Later resembles vulgatus. Bac. luteus L. and N. ^ 



4. Potaito is not characteristic during the first days; later, there 

 forms a distinct, wrinkled elevation. 



(a) The folds are padded, like coils of intestine. Bac. vulgatus 

 (Pliigge) Migula (p. 323). 



(ft) The folds are low, reticulated. Growth yellowish. Bac. 

 mesentericus (Fliigge) Lehm. and Neum. (p. 326). 



(c) Growth moist, wrinkled, besides the potato is deep black. Bac. 

 aterrimus Lehm. and Neum. (p. 328). 



(d) Growth rose-colored, a little wrinkled, gelatin smoky brown. 

 Compare also Bac. mesentericus ruber. Bac. gangrsenae pulpae 

 Arkovy (L. and N.) (p. 328). 



5. The potato growth is delicate, syrupy, clear. Bac. liodermos 

 (Fliigge) Lehm. and Neum. (p. 328). 



II. Anaerobic Vaeieties (of which, certainly, partially aero- 

 bic forms exist). Only exceptionally form long threads. Staining by 

 Gram's method rarely well developed (the Bac. tetani stains well). 

 Spontaneous motion dependent upon peritrichous flagella is rarely 

 lacking. The spore is usually located at the end ( paraplectrum form) 

 or at the middle, usually with some bulging (Clostridium form). In 

 most varieties both forms of sporulation occur. The recognition of 

 the individual varieties, which is often very difficult, and even impos- 

 sible, may be rendered somewhat easier by means of the following 

 scheme : 



(A) Pathogenic Varieties. — 



Wittlin (C. B L. II, 475) ; and since then, so far as we know, it has 

 not been upheld. 



^ For more details regarding this organism, compare Bacillus luteus 

 sporogenes Wood Smith and Baker (B. C. L. iv, p. 788). 

 20 



