26S 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Wlien it is desired to make a potato preparation, both ends of a large 
potato are cut off, and the plugger is passed through it by a rotary verti- 
cal movement. The potato cylinder, which appears in the plugger, should 
be long enough to reach a short distance into the hollow handle, so that 
it will be held firmly. By passing the curved knife into the potato 
cylinder and across its diameter in contact with the sides of the opening 
in the plugger, the cylinder is divided. The outer piece of the divided 
cylinder will fall out, and the piece which remains in the plugger now 
has a levelled surface for inoculation, and it can be removed by pushing 
it up a short distance into the hollow handle of the plugger. 
The thin end of the section should be trimmed off for the distance 
of about Ir in. to prevent its curling, and a notch should be made 
in the side of the end of the cylindrical portion of the section to admit 
the passage of moisture from the water reservoir of the culture-tube to the 
potato chamber above it. Fig. 36 represents the potato section placed 
in a reservoir-tube ready for use. 
(4) Staining- and Injecting-. 
Staining Bacteria to demonstrate the Flagella.* — Mr. Amos P. 
Brown writes as follows : — “ Among the most difficult objects to demon- 
strate that the microscopist has to deal with must be ranked the flagella 
or motile organs of the bacteria. So exceedingly thin and hyaline are 
they that it requires very skilful manipulation to see them even with 
the highest angle immersion objectives. Yet by means of staining 
methods I have been enabled to produce some preparations in which the 
flagella of Spirillum undula may be seen with a 1-in. objective. To see 
them properly, however, when the forms are as nearly as possible in 
their natural condition, requires a good 1/5 in. About two years ago I 
commenced a series of experiments as to the action of various stains on 
the common putrefactive bacteria, with the especial object of demon- 
strating the flagella. After trying the methods recommended by Loeffler, 
Trenckmann, and others for this purpose, I at last developed the follow- 
ing method, which is now published for the first time. 
* ‘The Observer,’ iii. (1892) pp. 298-300. 
