On the Biological Examination of Water and Milk. 39 
methods, viz., carbolic acid and heat combined. Dr 
Vincent’s method is as follows :—One drop of a 5 per cent. 
' solution of carbolic acid is added to each 2 c.c. of sterilised 
broth. He prefers to work with 8 cc. of broth: this would 
therefore require 4 drops of the 5 per cent. solution of 
carbolicacid. He takes six such tubes of carbolised broth, and 
to each he adds from 5 to 15 drops of the suspected water. 
He then places the tubes in an incubator at a temperature of 
42° C. If the typhoid bacilli be present, the broth turns 
cloudy in from eight to twelve hours. From these tubes 
inoculations are made into other tubes of carbolised broth, 
and the same process is repeated a third or fourth time; 
finally the bacilli are seeded into pure non-carbolised broth 
which has been thoroughly sterilised. According to Dr 
Vincent, the typhoid bacilli change their form in the 
carbolised broth (appearing as short twin bacilli and 
diplococci), but regain their usual rod form when transferred 
into non-carbolised broth. The motility of the bacilli is also 
considerably diminished in the carbolised medium: 
3. The differential staining method was introduced by 
Noeggerath’? about three years ago. It has more recently 
been employed by Grancher and Deschamps? for isolating the 
typhoid bacillus. The success of the method depends on the 
quality possessed by this particular bacillus to take up and 
retain certain of the analine dyes in preference to others. 
Holtz considers the test by itself of little value, but when 
combined with other methods of isolation, a most useful one 
for accurate diagnosis. Grancher and Deschamp’s formula 
runs thus :— 
Concentrated solution of methyl blue, 2c.c. 
cP », gentian violet, 4 c.c. 
methyl green, 1lc.c. 
chrysoidin, 46.8 
33 a) 
23 ») 
a », fuchsin, 5 e.e, 
Mix and dilute with 200 c.c. of water. 
Take from 7 to 10 drops of this stain to every 10 grams of 
nutrient gelatine; sterilise, seed with suspected material, 
1 Die Fortschritte der Medicin, Bd. vi., 1888. 
” Archives de Medicine Experiment, et d’Anatomie Pathol., Heft 1, 1889. 
