174 TEXT-BOOK OF BACTERIOLOGY. 



This bacillus has no pathogenic qualities, and even large quan- 

 tities of it may be introduced into the system with impunity. If 

 spores of Bac, subtilis are introduced into the blood of an animal 

 they are soon expelled again, being deposited in the liver and 

 spleen, as has been proved by Wj'ssokowitsch. Here they may 

 remain for months without exercising any influence on their sur- 

 roundings and without themselves being altered — i.e., killed. 



This negative behavior is worthy of remark, inasmuch as for- 

 merly, when it was not yet possible to distinguish the different 

 species of bacteria by discriminative marks and signs, as we do 

 at the present day, the hay bacillus was confounded with the 

 anthrax bacillus, on account of a certain superficial resemblance in 

 the form of their cells. It was intended to change anthrax bacilli 

 into harmless hay bacilli, and, vice versa, to breed from the latter 

 virulent anthrax, but nothing has been heard of the success of this 

 magnificent intention. 



Root-form Bacillus. 



The root-shaped bacillus is a species which has taken its name 

 from the appearance of its colonies on the gelatin plate. It is 

 pretty common in river- water and well-water, and occurs almost 

 everywhere in the upper layers of the soil in gardens and fields. 



Its rods are about as long as those of Bac. subtilis, but thicker. 

 The corners are very little rounded ; the cell contents are homo- 

 geneous. The separate members have a tendency to remain to- 

 gether after segmentation, and thus we often find very long chains 

 and threads. The root bacillus possesses a very slight power of 

 spontaneous motion, and it requires very careful and repeated ob- 

 servation to be convinced of the change of place which the cells 

 effect. Spores occur as large, egg-shaped, glittering bodies (grow- 

 ing in the middle of the cell), and, like those of Bac. megaterium, 

 are peculiarly suited for double staining. The bacillus belongs to 

 the strictly aerobic species, and thrives at ordinary temperatures 

 and also in the incubator. It may be stained in the usual manner. 



The forms of the colonies on the glass plate are very peculiar. 

 At first they appear as whitish, cloudy spots, which, however, soon 

 reach the surface, liquefy the gelatin, and then develop further in a 

 peculiar manner. From the centre of the whitish-gray colony ex- 

 tending to a distance are the twisted and branched outshoots, 

 which at the very first glance remind one of the tangled roots of 

 a tree. From the chief diverging lines others proceed which cross 

 one another at numerous points, and so produce an elegant and 



