142 NON-PATHOGENIC BACTERIA. 



bacillus very closely. It frequently shows in its centre a 

 large, resistant spore. It occasionally forms chains of vary- 

 ing length. It possesses terminal flagella; is exceedingly 

 motile ; and is a strict aerobe, growing very rapidly at the 

 room temperature and upon all ordinary culture-media. 

 Luxuriant growths, white in color, are formed, with lique- 

 faction of the gelatin. It is stained readily with the anilin 

 dyes. 



The organism can be obtained in pure culture by making 

 an infusion in water or beef-tea with finely cut hay. Boil for 

 fifteen minutes, and then place in the incubator for forty- 

 eight hours. The resistant spores, which have survived the 

 boiling, develop into fully matured germs and form a thick 

 white scum on the surface of the liquid. 



Bacillus mesentericus vulgatus : This germ, known also as 

 the potato bacillus, is found on potatoes, on the ground, and 



FIG. 49. FIG. 50. 



Bacillus mesentericus vulgatus. 



occasionally in milk. It is a very short, thick rod, with 

 rounded ends, frequently occurring in pairs (Fig. 50). It 

 has terminal flagella, is excessively motile, and reproduces 

 itself by sporulation. It stains with the anilin dyes and also 

 by Gram's method. It is strongly aerobic, growing quite 

 rapidly at the room temperature, especially in the presence 

 of oxygen. 



Gelatin is liquefied ; milk is coagulated. On potato a heavy, 

 wrinkled, brown or pink membrane is formed. This mem- 

 brane is detached easily (Fig. 49). A culture of the potato 



