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 glass.

(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 shell (Fig. 141, a).

Amœboid: Very irregular, streaming (Fig. 141, b).

Mycelioid: A filamentous colony, with the radiate character of a mould (Fig. 141, c).

Filamentous: An irregular mass 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.

(C) Surface Elevation.—

1. General Character of Surface as a Whole:

Flat: Thin, leafy, spreading over the surface (Fig. 143, a).

Effused: Spread over the surface as a thin, veily layer, more delicate than the preceding.

Raised: Growth thick, with abrupt terraced edges (Fig. 143, b).

Convex: Surface the segment of a circle, but very flatly convex (Fig. 143, c).

Pulvinate: Surface the segment of a circle, but decidedly convex (Fig. 143, d).

Capitate: Surface hemispherical (Fig. 143, e).

Umbilicate: Having a central pit or depression (Fig. 143, f).

Conical: Cone with rounded apex (Fig. 143, g).

Umbonate: Having a central convex nipple-like elevation (Fig. 143, h).

2. Detailed Characters of Surface:

Smooth: Surface even, without any of the following distinctive characters.

Alveolate: Marked by depressions separated by thin walls so as to resemble a honeycomb (Fig. 144).

Punctate: Dotted with punctures like pin-pricks.

Bullate: Like a blistered surface, rising in convex prominences, rather coarse.

Vesicular: More or less covered with minute vesicles due to gas formation; more minute than bullate.

Verrucose: Wart-like, bearing wart-like prominences.

Squamose: Scaly, covered with scales.

Echinate: Beset with pointed prominences.

Papillate: Beset with nipple or mamma-like processes.

Rugose: Short irregular folds, due to shrinkage of surface growth.

Corrugated: In long folds, due to shrinkage.

Contoured: An irregular but smoothly undulating surface, resembling the surface of a relief map.

Rimose: Abounding in chinks, clefts, or cracks.

(D) Internal Structure of Colony (Microscopical).—

Refraction Weak: Outline and surface of relief not strongly defined.

Refraction Strong: Outline and surface of relief strongly defined; dense, not filamentous colonies.

1. General:

Amorphous: Without any definite structure, such as is specified below.

Hyaline: Clear and colourless.

Homogeneous: Structure uniform throughout all parts of the colony.

Homochromous: Colour uniform throughout.

2. Granulations or Blotchings:

Finely granular.

Coarsely granular.

Grumose: Coarser than the preceding, with a clotted appearance, and particles in clustered grains (Fig. 145, a).

Moruloid: Having the character of a mulberry, segmented, by which the colony is divided in more or less regular segments (Fig. 145, b).

Clouded: Having a pale ground, with ill-defined patches of a deeper tint (Fig. 145, c).

3. Colony Marking or Striping:

Reticulate: In the form of a network, like the veins of a leaf (Fig. 146, a).

Areolate: Divided into rather irregular, or angular, spaces by more or less definite boundaries.

Gyrose: Marked by wavy lines, indefinitely placed (Fig. 146, b).

Marmorated: Showing faint, irregular stripes, or traversed by vein-like markings, as in marble (Fig. 146, c).

Rivulose: Marked by lines like the rivers of a map.

Rimose: Showing chinks, cracks, or clefts.

4. Filamentous Colonies:

Filamentous: As already defined.

Floccose: Composed of filaments, densely placed.

Curled: Filaments in parallel strands, like locks or ringlets (Fig. 147).

(E) Edges of Colonies.—

Entire: Without toothing or division (Fig. 148, a).

Undulate: Wavy (Fig. 148, b).

Repand: Like the border of an open umbrella (Fig. 148, c).

Erose: As if gnawed, irregularly toothed (Fig. 148, d).

Lobate.

Lobulate: Minutely lobate (Fig. 149, e).

Auriculate: With ear-like lobes (Fig. 149, f).

Lacerate: Irregularly cleft, as if torn (Fig. 149, g).

Fimbriate: Fringed (Fig. 149, h).

Ciliate: Hair-like extensions, radiately placed (Fig. 149, j).

Tufted.

Filamentous: As already defined.

Curled: As already defined.

(F) Optical Characters (after Shuttleworth).—

1. General Characters:

Transparent: Transmitting light.

Vitreous: Transparent and colourless.

Oleaginous: Transparent and yellow; olive to linseed-oil coloured.

Resinous: Transparent and brown, varnish or resin-coloured.

Translucent: Faintly transparent.

Porcelaneous: Translucent and white.

Opalescent: Translucent; greyish-white by reflected light.

Nacreous: Translucent, greyish-white, with pearly lustre.

Sebaceous: Translucent, yellowish or greyish-white.

Butyrous: Translucent and yellow.

Ceraceous: Translucent and wax-coloured.

Opaque.

Cretaceous: Opaque and white, chalky.

Dull: Without lustre.

Glistening: Shining.

Fluorescent.

Iridescent.

2. Chromogenicity:

Colour of pigment.

Pigment restricted to colonies.

Pigment restricted to medium surrounding colonies.

Pigment present in colonies and in medium.

Streak or Smear Cultures.—

Gelatine and Agar.—Note general points as indicated under plate cultivations.

Inspissated Blood-serum.—Note the presence or absence of liquefaction of the medium. (The presence of condensation water at the bottom of the tube must not be confounded with liquefaction of the medium.)

All Oblique Tube Cultures.—

1. Colonies Discrete: Size, shape, etc., as for plate cultivations (vide page 261).

2. Colonies Confluent: Surface elevation and character of edge, as for plate cultivations (vide page 263).

Chromogenicity: As for plate cultures.

Gelatine Stab Cultures.—

(A) Surface Growth.—As for individual colonies in plate cultures (vide page 261).

(B) Line of Puncture.—

Filiform: Uniform growth, without special characters (Fig. 150, a).

Nodose: Consisting of closely aggregated colonies.

Beaded: Consisting of loosely placed or disjointed colonies (Fig. 150, b).

Papillate: Beset with papillate extensions.

Echinate: Beset with acicular extensions (Fig. 150, c).

Villous: Beset with short, undivided, hair-like extensions (Fig. 150, d).

Plumose: A delicate feathery growth.

Arborescent: Branched or tree-like, beset with branched hair-like extensions (Fig. 150, e).

(C) Area of Liquefaction (if present).—

Crateriform: A saucer-shaped liquefaction of the gelatine (Fig. 151, f).

Saccate: Shape of an elongated sack, tubular cylindrical (Fig. 151, g).

Infundibuliform: Shape of a funnel, conical (Fig. 151, h).

Napiform: Shape of a turnip (Fig. 151, j).

Fusiform: Outline of a parsnip, narrow at either end, broadest below the surface (Fig. 151, k).

Stratiform: Liquefaction extending to the walls of the tube and downward horizontally (Fig. 151, l).

(D) Character of the Liquefied Gelatine.—

1. Pellicle on surface.

2. Uniformly turbid.

3. Granular.

4. Mainly clear, but containing flocculi.

5. Deposit at apex of liquefied portion.

(E) Production of Gas Bubbles.

Shake Cultures.—

1. Presence or absence of liquefaction.

2. Production of gas bubbles.

3. Bulk of growth at the surface—aerobic.

4. Bulk of growth in depths—anaerobic.

Fluid Media.

1. Surface of the Liquid.—

Presence or absence of froth due to gas bubbles.

Presence or absence of pellicle formation.

Character of pellicle.

2. Body of the Liquid.—

Uniformly turbid.

Flocculi in suspension.

Granules in suspension.

Clear, with precipitate at bottom of tube.

Colouration of fluid, presence or absence of.

3. Precipitate.—

Character.

Amount.

Colour.

Carbohydrate Media.—

Growth.

Reaction.

Gas formation.

Coagulation or not of serum albumen (when serum water media are employed).

Litmus Milk Cultivations.—

{Unaltered.

1. Reaction: {Acid.

{Alkaline.

2. Odour.

3. Formation of gas.

{Unaltered.

4. Consistency: {Peptonised (character of solution).

{Coagulated.

{hard: solid.

5. Clot: Character {soft: floculent.

{ragged and broken up by gas bubbles.

(a) Coagulum undissolved.

(b) Coagulum finally peptonised, completely: incompletely.

Resulting solution, clear: turbid.

{Abundant.

{Scanty.

6. Whey: {Clear.

{Turbid.

{Coagulated by boiling, or not.