I.] THE HISTORY OF THE COMMA-BACILLUS. 9 



magnifying power a small drop of meat-broth cultivation on 

 a cover-glass. It is seen then that the comma-bacilli move 

 in a very lively manner. When they are collected together 

 at the edge of the drop, and are moving about amongst one 

 another, they look like a swarm of dancing midges, and 

 those long spiral threads appear also moving in an animated 

 manner, so that the whole affords a strange and extremely 

 characteristic picture. 



" But the comma-bacilli also grow in other liquids, and 

 especially, in great abundance and speedily, in milk. They 

 do not make milk curdle, and do not precipitate the casein, 

 which many other bacteria, which can also be raised in milk, 

 do. Hence the milk looks quite unchanged ; but if you take 

 a small drop from the surface, and examine it under the 

 microscope, it teems with comma-bacilli. They also grow in 

 the serum of blood, in which they also very quickly develop 

 and multiply in great numbers. A very good soil for the 

 reproduction of comma-bacilli is also nutritive gelatine. 

 This gelatine also serves for facilitating and securing the 

 discovery of comma-bacilli ; for the colonies of comma- 

 bacilli assume in the gelatine a most characteristic and 

 definite form, which, so far as I can discern, and as far as 

 my experience reaches, no other kind of bacteria assumes in 

 like manner. 1 



" The colony looks, when it is very young, like a very 

 pale and tiny little drop, which is, however, not quite cir- 

 cular, the shape generally assumed by these bacteria-colonies 

 in gelatine ; but it has a more or less irregularly bordered, 

 hollowed out, in parts also rough or jagged, shape. It also 

 has, at a very early stage, rather a granulated appearance, 

 and is not of such regular character as in other colonies of 

 bacteria. 



1 This is not strictly correct, as will be shown later. 



