On the Cultivation of Bacteria. By Edgar M. Crookshank. 29 



can study the relative position of the individual micro-organisms 

 one to another, and in some cases very beautiful preparations 

 result. A perfectly clean cover-glass is carefully deposited on a 

 plate, or potato-cultivation, and gently and evenly pressed down. 

 One edge is then levered up with a needle, and the cover-glass 

 lifted ojff by means of forceps. The preparation is then allowed to 

 dry, passed three times through the flame, and stained as already 

 described. In the case of plate-cultivations, especially where no 

 liquefaction has taken place, the growth is bodily transferred to 

 the cover-glass, and a vacant area mapped out on the jelly corre- 

 sponding exactly with the form and size of the cover-glass which 

 was employed. 



In illustration of this method, I would call attention to a 

 bacillus occasionally present in the air, of which I have been unable 

 to find any written description, and for which I would suggest the 

 name Bacillus figurans. (Plate III. figs. 1 and 2.) 



In plate-cultivations this bacillus produces a cloudiness which 

 gradually creeps over the surface of the gelatin. If a preparation 

 is made in the manner I have just described, this growth is found 

 to consist of rods which vary considerably in length. These rods 

 lie parallel to one another, and form rows or chains which become 

 twisted at intervals into the most curious convolutions, from which 

 ofishoots are continued in various directions. These long shoots 

 or processes become in turn at intervals twisted into varying shapes 

 and figures. If nutrient jelly in a test-tube be inoculated with a 

 platinum needle charged with the bacilU, the growth appears in 

 the form of windings on the free surface which are visible to the 

 naked eye, from these fine filaments spread downwards into the 

 substance of the jelly. Cultivated on a sloping surface of nutrient 

 agar-agar the filaments spread transversely from the central streak, 

 giving a feathery appearance. 



Cheshire and Cheyne have described a peculiar mode of growth 

 of the Bacillus alvei in plate-cultivations, and Hauser has photo- 

 graphed the peculiar grouping of certain bacteria connected with 

 decomposition. 



An interesting phenomenon which Hauser has also observed 

 in connection with the last-mentioned bacteria, is the peculiar 

 individual movement which they possess on solid media. This can 

 be most conveniently studied by cultivating the bacilli in a glass 

 capsule. The bacilli often move singly, or meet and progress in 

 pairs, or form chain-like processions ; possibly the movements are 

 accounted for by the existence of a film of liquid as they are 

 observed only on solid media containing less than ten per cent, of 

 gelatin. 



We may also apply the method of plate-cultivation to the 

 examination of water, and to studying the bacteria which exist in 



