ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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of typhoid fever : — A 1 • 5 per cent, agar solution, made by dissolving the 
agar in bouillon, is first prepared. This is then cleared up, strained, and 
filtered. To the filtrate are added 2 per cent, lactose, 1 per cent, urea, 
and 30 per cent, litmus tincture. This is then distributed into test- 
tubes (10 ccm.) and steam sterilised for 10-20 miuutes. Cultivated in 
this medium, the difference as to production of acid between the two 
bacteria is rendered very striking. After inoculation, the medium may 
be poured into capsules and incubated at 37°. In from 16-18 hours, 
coli turns the blue colour of the medium quite red, the reaction of the 
condensation water being also acid. After 24 hours the medium again 
becomes blue, owing to ammoniacal decomposition of the urea. The 
colonies also turn blue, and the presence of ammonia can easily be ren- 
dered evident by touching the medium with a glass rod moistened with 
hydrochloric acid. When inoculated with typhoid bacilli there is no 
reaction to litmus, and the blue colour remains unchanged for 72 hours 
or more. The differences between the two may be rendered strikingly 
obvious by sowing them side by side in the same capsule. 
Cultivating Gonococcus. — Dr. J. de Christmas,* in an interesting 
communication on Gonococcus and gonotoxin, states that he has found 
rabbit serum to be an excellent medium for the cultivation of this 
microbe, and that human albuminous fluids, such as blood-scrum, ascitic 
fluid, or pleuritic exudation, mixed with peptonised gelose in the pro- 
portion of two to one, give abundant cultures. The preference is giveu 
to ascitic fluid, which is easy to obtain and easy to sterilise, as it will 
stand, without coagulating, a higher degree of heat than blood-serum. 
The mixture with gelose is perfectly clear, and stroke cultivations in- 
cubated at 35° develop abundantly in 24 hours. The cultures, how- 
ever, die off in 3 or 4 days, and have, therefore, to be resown every 
48 hours. This inconvenience is obviated by the use of coagulated 
rabbit serum, on which the microbe not only thrives freely but lives 
for at least 3 or 4 weeks. The difficulty in connection with rabbit serum 
is that it is obtainable only in small quantity, about 60 ccm. for one 
animal. For the study of gonotoxin such small amounts are quite 
insufficient, and the author used ascitic fluid mixed with peptonised 
bouillon in the proportion of 1 to 3. The bouillon was ordinary veal- 
bouillon, or was made with Liebig’s extract (0*5 grm. to the litre). 
The reaction of the medium should be slightly alkaline. 
Pure cultivations of Gonococcus were obtained by spreading a drop 
of the fresh pus upon the rabbit serum medium and incubating at 36^. 
In about 12 hours colonies of Gonococcus are well in advance of other 
organisms which may be present, and it is therefore quite easy, by once 
resowing, to obtain pure cultures. On rabbit serum the colonies are 
small, round, transparent, raised in the centre, isolated or confluent. 
Their chief characteristic is viscosity, which is well shown by the 
adhesion of the growth when touched with a platinum wire. The 
author explains the character of the distribution on cover-glass pre- 
parations as being due to this viscosity. It is also stated that the 
classic shape of Gonococcus always met with in pus is the least frequent 
in cultures. 
* Ann. Inst. Pasteur, xi. (1837) pp. 60D-.T3. 
