68 BACTERIA IN RELATION TO PLANT DISEASES. 
them.* Some of them are very sen- 
sitive to the presence of acids, alka- 
lies, strong alcohol, or antiseptics, or 
their action is inhibited by the pres- 
ence of other enzymes or of products 
of enzymic fermentation in excess, or 
by the absence of some combining 
substance, such as lime or some weak 
acid. Some do not pass readily 
through the Chamberland filter or 
eS 
{mt 
wpe 
/ 
ie 
3 
Tr 
TTITITTT TTT Te 
Ea = through filter papers. Some are 
= E- destroyed at lower temperatures after 
Es = precipitation. Some are not pro- 
= Hi > duced except in presence of the sub- 
= : stance which they can decompose, 
E4 : but this is not true of all. Usually 
E3 j an organism produces more than 
one ferment and some bacteria are 
known to produce five or six. Bac 
tertum campestre produces at least 
three and probably four, viz, diasta- 
sic, cytohydrolytic, proteolytic, and 
rennet. It also inverts cane-sugar, 
but it is not yet known whether this 
change is accomplished by means of 
an invertase. On enzymes derived 
from bacterial soft-rot organisms the 
reader should consult recent papers 
by Jones (Centralb. f. Bakt, 2 Abt., and 
Vermont Exp. Sta. Rep.). Levy has 
published an interesting paper on 
“Some physical properties of en- 
zymes” (The Jour. Infect. Diseases, 
Vol. II, 1905, pp. 1-48). 
For concentrating fluids in vacuo 
at low temperatures (50° to 60° C.) 
Fig. 59.4 the thick-walled Kitasato flask shown 
*The same amount of dry heat does not affect them, and Loeffler has recently advised exposure 
of thoroughly air-dried tissues and cultures to 150° C., dry heat, as an easy way of eliminating the 
bacteria prior to grinding and extraction of the uninjured enzymes and other soluble products. 
Non-sporiferous bacteria may be heated at 120° C, for2to3hours. ‘Tissuesand sporiferous bacteria 
should be heated at 150° C. for one-half hour. (Deutsche Med. Wochenschrift, Dec. 22, 1904.) 
+Fic. 59.—Burettes used by the writer for titrating culture media. ‘Twentieth-normal sodium 
hydrate is used to determine the acidity, and the medium is finally brought to the desired alkalinity 
with quadruple-normal sodium hydrate. The fluid is boiled and titrated hot, using phenolphthalein 
as the indicator. The burettes should be graduated to tenths of a cubic centimeter and should hold 
50 cc. Alkali should not be allowed to stand in them. 
