RAW CULTURE MEDIA. 41 
The same media, and as many other sorts as are available, should be tested raw 
in sterile, dry, Petri dishes 10 cm. broad and 2 to 3 cm. deep. For this purpose the 
vegetables are prepared as follows: First, select sound, clean specimens, especially 
avoiding those which are cracked open; next, scrub their surface thoroughly under 
the tap, and rinse them in distilled water. They are now soaked 5 or 10 minutes, 
or even 20 minutes, in 1:1000 water solution of mercuric chloride. ‘They are then 
removed and dried with or without a preliminary rinsing in sterile water. When 
dry they are put on a sterile paper or plate, are cut into slices about 1.5 to 2 cm. 
thick with a cold sterile knife, are picked up with sterile forceps, and are put into 
the Petri dishes in pairs 
or fours, the cover being 
immediately replaced. 
Enough of the mercuric 
chloride remains on the 
surface to inhibit the 
growth of any surface 
organisms which have 
not been killed outright, 
and experience shows 
that intruders are rarely 
dragged over the’ cut 
surface. ‘The slices may 
be inoculated at once 
or after 36 hours incuba- 
tion in a moist chamber 
at 30° C., or 48 hours at 
25°C. The latter course 
_is preferable. In either 
case, half of the slices 
in each dish must be 
FRge kept uninoculated for 
comparison (fig. 36). ‘This method is well adapted to the study of various soft-rot 
organisms such as Bacillus carotovorus, B. aroidee, B. oleracea, etc. 
PLANT JUICES (WITH AND WITHOUT THE ADDITION OF WATER). 
(1) Juice of the host-plant. (4) Prune-juice. 
(2) Potato-broth. (5) Orange-juice. 
(a) With sodium hydrate. (6) Coconut-water (unsteamed).f 
(b) Without alkali. (7) Yellow corn-meal broth. 
(3) Cabbage or cauliflower broth. (8) Timothy-hay infusion. 
*F ic, 36.—Iris-rhizome-rot organism grown on raw carrot. The check piece is unchanged, the 
inoculated piece has browned and softened. Incubated 4 days at about 23° C. Anes : 
+This is removed directly from the nut to sterile test-tubes by means of sterile pipettes, which 
are useful in many ways. The pipettes should be dry-heated and kept from contamination in long, 
narrow, covered tin boxes. These boxes may be cylindrical or rectangular, with an end cover. 
The upper end of the pipette should be plugged firmly with cotton before sterilization, and this 
should be pushed in a short distance beyond the end, so that when the finger is placed on the end 
there will be an air-tight union. Scalpels, etc., should be sterilized in shorter boxes of the same 
kind (fig. 37). 
