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~3. Chemical Products of Growth.~--(_Vide_ Chemical Examination of Cultivations, page 276.)
Chromogenesis.
Photogenesis.
Enzyme formation.
Fermentation of carbohydrates: Acid formation.
Alkali formation.
Indol formation.
Phenol formation.
Reducing and oxidising substances.
Gas formation.
~4. Biology.~--(_Vide_ Physical Examination of Cultures, page 295.)
Atmosphere.
Temperature.
Reaction of nutrient media.
Resistance to lethal agents: Physical: Desiccation.
Light.
Colours.
Chemical germicides.
Vitality.
~5. Pathogenicity:~
Susceptible animals, subsequently arranged in order of susceptibility.
Immune animals.
Experimental inoculation, symptoms of disease.
Post-mortem appearances.
Virulence: Length of time maintained.
Optimum medium?
Minimal lethal dose.
Exaltation and attenuation of virulence?
Toxin formation.
MACROSCOPICAL EXAMINATION OF CULTIVATIONS.
In describing the naked-eye and low-power appearances of the bacterial growth the descriptive terms introduced by Chester (and included in the following scheme) should be employed.
SOLID MEDIA.
~Plate Cultures.~--
_Gelatine._--Note the presence or absence of liquefaction of the surrounding medium. If liquefaction is present, note shape and character (_vide_ page 269, "stab" cultures).
_Agar._--No liquefaction takes place in this medium. The liquid found on the surface of the agar (or at the bottom of the tube in agar tube cultures) is merely water which has been expressed during the rapid solidification of the medium and has subsequently condensed.
_Gelatine and Agar._--Examine the colonies at intervals of twenty-four hours.
(a) With the naked eye.
(b) With a hand lens or watchmaker's gla.s.s.
(c) Under a low power (1 inch) of the microscope, or by means of a small dissecting microscope.
Distinguish superficial from deep colonies and note the characters of the individual colonies.
(A) ~Size.~--The diameter in millimetres, at the various ages.
(B) ~Shape.~--
Punctiform: Dimensions too slight for defining form by naked eye; minute, raised, hemispherical.
Round: Of a more or less circular outline.
Elliptical: Of a more or less oval outline.
Irregular: Outlines not conforming to any recognised shape.
Fusiform: Spindle-shaped, tapering at each end.
Cochleate: Spiral or twisted like a snail sh.e.l.l (Fig. 141, a).
[Ill.u.s.tration: FIG. 141.--Types of colonies: a, Cochleate; b, amoeboid; c, mycelioid.]
Amoeboid: Very irregular, streaming (Fig. 141, b).
Mycelioid: A filamentous colony, with the radiate character of a mould (Fig. 141, c).
Filamentous: An irregular ma.s.s of loosely woven filaments (Fig. 142, a).
Floccose: Of a dense woolly structure.
Rhizoid: Of an irregular, branched, root-like character (Fig. 142, b).
Conglomerate: An aggregate of colonies of similar size and form (Fig.
142, c).
Toruloid: An aggregate of colonies, like the budding of the yeast plant (Fig. 142, d).
Rosulate: Shaped like a rosette.
[Ill.u.s.tration: FIG. 142.--Types of colonies: a, Filamentous; b, rhizoid; c, conglomerate; d, toruloid.]
(C) ~Surface Elevation.~--
1. _General Character of Surface as a Whole_:
