Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . Fig. 32.—Staphylococcus pyogenes aureus: colony two days old, seenupon an agar-agar plate (X40) (Helm). small dot, like a fly-speck, to that resembling a small are elevated, some depressed, and some, like cholera,cup-shaped—umbUicated. Then they are variously pigmented. Some liquefy gelatinspeedily, others not at all. The appearances of a few areso characteristic as to be recognized at a glance. Someproduce gas-bubbles. 88 ESSENTIALS OF BACTERIOLOGY Microscopi
Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . Fig. 32.—Staphylococcus pyogenes aureus: colony two days old, seenupon an agar-agar plate (X40) (Helm). small dot, like a fly-speck, to that resembling a small are elevated, some depressed, and some, like cholera,cup-shaped—umbUicated. Then they are variously pigmented. Some liquefy gelatinspeedily, others not at all. The appearances of a few areso characteristic as to be recognized at a glance. Someproduce gas-bubbles. 88 ESSENTIALS OF BACTERIOLOGY Microscopic—Use a low-power lens, with the Abbenearly shut out—that is the narrowest blender. The stage ofthe microscope should be of such size as to carry a Petrisaucer easily upon it. The second dilution or third plate is usually made use o±—that one containing the colonies suf&ciently isolated. These isolated ones should be sought for, and their appear-ance well noticed. There may be two or three forms from the same germ, thedifference due to the greater or less amount of oxygen that. Fig. 33-—Microscopic appear-ances of colonies. Fig. 34.—Klatsch preparations. they have received, or the greater or less amount of spacethat they have had to develop in. The microscopic picture varies greatly; now it is like thegnarled roots of a tree, and now like bits of frosted glass;some bacteria have quite characteristic colonies (Fig. 32). Impression or Klatsch Preparations.—In ordermore thoroughly to study a certain colony and to make apermanent specimen of the same, we press a clean cover-glassupon the particular colony, and it adheres to the glass. Itcan then be stained or examined. The Germans give thename of Klatsch to such preparations. Fishing.—To obtain and examine the individual members THE GROWTH AND APPEARANCES OF COLONIES 89 of a particular colony the process of fishing, as it is called, isresorted to. The colony having been placed under the field of the micro-
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