124 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
artificial nutrient media. The medium is composed of meat-broth 500 
ccm. (250 grm. meat), grape sugar 12*5 grm., and 25*0 grm. of an 
alga mixture, chiefly Porphyra vulgaris. This is boiled, neutralized, 
filtered, and sterilized in glass vessels. 
A single species is isolated from its natural habitat and separated from 
bacteria, &c., by means of a capillary glass tube ; the external diameter 
of this is 0*4-0 *6 mm., the lumen about 0*3-0 *5 mm., and the length 
10-20 cm. One end of the tube is immersed in the medium, and when 
all but 1-2 cm. is filled it is removed to the fluid containing the Bacteria 
and Infusoria, and the remaining space completely filled. The two fluids 
must not be separated by an air-bubble. Both ends of the capillary tube 
are then sealed up in the flame. In from 5-30 minutes the Infusoria 
will be found on microscopical examination to have invaded the medium, 
and when they have removed several centimetres from the original fluid 
the spot is marked under the Microscope, broken off, and the end melted 
up. In this way one or several Infusoria may be isolated and kept alive 
for a month, but on the whole they do not thrive in the capillary tube. 
So the medium, placed in test-tubes, is inoculated with the contents of 
a tube which has been ascertained to be pure. The ends are broken off 
and the contents blown in. The Infusoria grow slowly, and clouding 
of the medium is not visible to the naked eye for 7 or 8 days, though 
microscopical examination will reveal presence of the organisms before 
this. After a time a distinct scum forms on the surface. 
Polytoma uvella can also be grown on solid media by making plate 
cultivations and inoculating them from the fluid in which they are 
contained. 
The colony on the plate may be recognized as a little white point in 
from 7 to 8 days. In 2 to 3 weeks it attains size of a millimetre. There 
is no liquefaction of the gelatin. The colonies are mostly round, and 
the centre of the larger ones dark and somewhat yellowish, while the 
periphery is greenish. The form and structure of the cells is easily made 
out, but their movements are sluggish. 
Puncture cultivations also succeeded, though the colonies along the 
track were less strong than those on the surface. 
Puncture Cultivations.* — Dr. Beneke points out that puncture cul- 
tivations can be rendered much more useful if the needle be thrust 
into the medium close to the glass instead of being stuck down the 
centre of the tube. This could be done with the ordinary straight 
needle, but better if it be bent to the shape of a bayonet. In this 
way the growing colonies can be observed microscopically even with 
objectives of short focus. 
Culture Media for Biochemic Investigations.!— Dr. E. A. de 
Schweinitz finds that Fermi’s solution — which consists of 1000 ccm. H 2 0, 
0 * 2 grm. magnesium sulphate, 1 * 0 grm. acid potassium phosphate, 
10 grm. ammonium phosphate, and 45 grm. glycerin — forms an excellent 
basis for general cultivation purposes when mixed with nutrient sub- 
stances appropriate to the particular organisms. Thus, for hog-cholera 
and swine-plague 1 per cent, agar is added, and in this medium the 
* Centralbl. f. Bakteriol. u. Parasitenk., xiv. (1893) pp. 174-5. 
t New York Med. Journ., lvii. (1893) p. 267. 
