BACILLUS SUBTILIS. 277 



axis, and at the same time bend to and fro. Individuals suddenly 

 stand still, then hasten on again. The spirals found under 

 such circumstances in all probability belong 

 to Spirochate jdicatilis, the Spirochcete of 

 marshes. If these spirals are allowed to 

 dry, and are stained, we shall see that they are 

 not unicellular, but consist of successive seg- 

 ments, which may vary in length according 

 to circumstances. Very fine Spirochcete can 

 usually be obtained by keeping in a warm 

 place a filtered infusion of pea-flour. ftv m.Spirochate 



Pure Cultures. Bacillus subtilis. Vfe plicaiilis, after -aniline 



staining, partially show- 

 will now endeavour to follow without a break ing the segmentation into 



the developmental history of a bacteriad, rodlets 

 selecting the hay bacillus for the purpose. We first of all soak 

 some dry hay in the smallest possible quantity of spring water, and 

 let the infusion stand for four hours in a warm chamber at a 

 constant temperature of 36 C. 1 We then pour off the infusion, 

 without filtering, and dilute it down, if too strong, to a specific 

 gravity of 1-004, or a pale sherry colour. Now place the fluid in 

 a flask holding at least 500 c.cm. The flask is stopped with a plug 

 of cotton -wool, and the fluid boiled very gently for an hour. Then 

 let the temperature sink to, and remain at 36 C. 1 In the course 

 of a day, or a day and a half, a delicate grey skin, the pellicle, will 

 have formed on the surface of the fluid ; this consists of the 

 zooglcea stage of Bacillus subtilis, the bacteriad of hay. We have 

 made use of the power possessed by the spores of this bacteriad, 

 of resisting boiling heat for a considerable time, in order to obtain 

 a pure culture of them. Of the pellicle obtained as above we now 

 transfer a little, with the platinum loop, to an object-slide, and 

 examine the object with the strongest magnification which we 

 have at command. We find the pellicle formed of long, segmented, 

 wavy threads, running parallel to one another. The threads remain 

 for the most part in position, because they are held together by an 

 invisible jelly (Fig. 104, A}. The threads consist of cylindrical 

 rodlets of various lengths in general, however, twice or thrice as 

 long as broad. The substance of the threads appears homogeneous, 

 colourless, pretty highly refractive. Even with the strongest 

 magnification no other structure is recognisable. With chlorzinc 



1 This temperature, though advantageous, is not essential. A warm 

 room temperature will suffice, but the action is slower. [ED.] 



