Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . sition is smeared on thesurface with the material, and the growth occurs along thesmear, or the medium is punctured with a stab of the plati-num rod containing the material, and the growth followsthe line of thrust. The former is called a stroke or smearculture, the latter a stab or thrust culture. INOCULATION OF CULTURE-MEDIA 79 Streaked Surface Plating.—The surface of the medium,hardened in a Petri dish, is scratched by a needle containingthe inoculating material, thr
Essentials of bacteriology; being a concise and systematic introduction to the study of bacteria and allied microörganisms . sition is smeared on thesurface with the material, and the growth occurs along thesmear, or the medium is punctured with a stab of the plati-num rod containing the material, and the growth followsthe line of thrust. The former is called a stroke or smearculture, the latter a stab or thrust culture. INOCULATION OF CULTURE-MEDIA 79 Streaked Surface Plating.—The surface of the medium,hardened in a Petri dish, is scratched by a needle containingthe inoculating material, three or more streaks being madewithout obtaining fresh material, so that the growth alongthe streak or scratches will represent varying amounts ofthe substance to be tested. In removing the cotton plugsfrom the sterile tubes to carry out the inoculation the plugsshould remain between the fingers in such a way that thepart which comes in contact with the mouth of the tube willnot touch anything (Fig. 23). It is well to pass the mouth of the tube and the cottonplugs through a flame, scorching the latter before reinserting. Fig. 23.—Maimer of holding plugs. Sterilizing Needle.—Sterilize needles by passing throughthe flame before and after each inoculation; also sterilize theglass part, as it is liable to become infected. After the needle has been withdrawn, the plugs are rein-serted and the tubes labeled with the kind and date of culture. Plate Cultures.—Several tubes of the culture-mediumare made Hquid by heating in water-bath, and then inocu-lated with the material as follows. A looped platinum needleis dipped into the material and then shaken in the tube ofliquid media (gelatin, agar, etc.). This first tube is called original. From this three drops(taken with the looped platinum rod, Fig. 11, p. 45) areplaced in a second tube, the rod being shaken somewhat in the 8o ESSENTIALS OF BACTERIOLOGY gelatin or agar; this is labeled first dilution (a colored pencilis useful for
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