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METHODS OF BACTERIOLOGICAL INVESTIGATIOy. 59

support the e^g sections. As the Qgg must be handled with the
fingers, the hands must be thoroughly washed, then soaked in
sublimate, 5 to 1000, and then washed again in absolute alcohol, to
remove the sublimate. The eggs are shelled while still hot, and
cut into two, three, or four sections. They are vaccinated in
points, upon the white ; the yellow is not so well adapted to cul-
ture experiments, since it cannot be cut with a smooth surface.
I always keep on hand sections of potato and egg, also tubes
of gelatine, agar-agar, and blood-serum ; and when in my prac-
tice particularly good material, or anything uncommon, presents
itself, a portion of it is at once transferred to these different cul-
ture media, so that it is pretty sure to develop in one of them
at least. For example, I have several times met with a bacterium
in the human mouth which produces a yellowish coloring-mat-
ter, and which absolutely refuses to grow on anything which I
have tried, except potato.
Liquid Media.
For studying the various processes of decomposition, fermenta-
tion, putrefaction, etc., brought about by bacteria, a great variety
of liquid media have been employed. One which I have used
extensively consists of water 100.0, peptone 2.0, sugar 1.0, beef
extract 1.5, with occasional additions of starch. This I have
found very well adapted to the culture and study of many oral
bacteria. Other media are milk, urine, bread-juice, juice of
fruits, decoctions or watery extracts of various plants or grains,
saliva (to which, however, nutrient material must be added), etc.
These may also be combined with each other in various propor-
tions.
Applicatiox of the above Methods to Cultivations from
THE Human Mouth.
/
For general work on the bacteria of the oral cavity the best
medium, in my opinion, is presented by neutral beef-water-pep-
tone-sugar-agar-agar. On this medium I first make line cul-
tures (which may be supplemented by dilution cultures at the
same time), and then for the further study of the micro-organ-
isms cultivated I make dilution cultures on gelatine, etc. It often