ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
239 
prolonged downwards to near the bottom of the bottle, and being 
narrowed so as to form an elongated funnel. The neck T is closed by 
a metal cap K, from inside of which passes a wire ending in a loop. 
The loop picks up just the necessary quantity of oil, provided that the 
bottle be not filled too much. Owing to its broad base the bottle is 
very steady, and if S be closed with a cork there is no fear of any over- 
flow, as the bottle then acts as a siphon. For travelling, the metal cap 
must be replaced by a cork. 
B. Technique.* 
(1) Collecting- Objects, including- Culture Processes. 
Alkalised Serum as a Culture Medium for Diphtheria Bacilli.f — 
Dr. L. Cobbett prepares alkalised ox-serum in the following way. To 
every 100 ccm. of the serum 2 grm. of glucose and 1 * 75 ccm. of a 10 per 
cent, solution of NaHO are added. The mixture is then put into tubes 
and sterilised in an autoclave at a higher pressure than usual. This is 
effected by closing the exit tap of the autoclave before the air which it 
contains has been expelled, and thus the pressure of the heated air is 
added to that of the steam. The medium is of a rich brown hue, and 
should be perfectly transparent by transmitted light. On it the colonies 
are discrete, flat, grey, or almost colourless, and after several days’ 
growth their margins usually became indented and radially fissured. 
Alkalised horse-serum, from which more rapid results are obtained, 
is prepared as follows. To every 100 ccm. of serum 2 grm. of glucose 
and from 1 • 25 to 1*2 ccm. of a 10 per cent, solution of NaHO are added. 
The mixture is then poured into tubes and Petri’s dishes, and sterilised 
at a temperature of 90° C. on 2 successive days in a chamber surrounded 
by a jacket containing boiling water. Thus prepared the medium is 
bright, transparent, and almost as light in colour as gelatin. Colonies 
may be seen on it after from 6 to 8 hours’ incubation ; the colonies are, 
however, not so radially striated (daisy-shaped) as with ox-serum. 
The impression method of examining the growth is recommended, as 
thereby a large number of colonies can be examined at once. 
Preserving Living Pure Cultivations of Water Bacteria 4 — Mr. J. 
Lunt finds that water bacteria can be preserved in sterilised tap water 
for considerable periods without impairment of vitality or of their cha- 
racteristic and specific features. This simple method has the following 
advantages. (1) It obviates the necessity of frequently transplanting 
cultures to fresh media; such cultures remain in good condition for 
periods during which they would have died on the ordinary media. 
(2) The cultures are preserved in their natural habitat, and, when re- 
sown, grow vigorously. (3) The method serves also to differentiate 
those organisms which may properly be classed together as water bac- 
teria from those outside the water group. 
The experiments were made with B. fluorescens liquefaciens ; fluores - 
* This subdivision contains (1) Collecting Objects, including Culture Pro- 
cesses ; (2) Preparing Objects ; (3) Cutting, including Imbedding and Microtomes ; 
(4) Staining and Injecting ; (5) Mounting, including slides, preservative fluids, &c. ; 
(6) Miscellaneous. t Lancet, 1898, i. pp. 362-3. 
X Trans. Brit. Inst. Preventive Med., 1st series, 1897, pp. 152-63. 
