. Pathogenic micro-organisms, including bacteria and Protozoa; a practical manual for students, physicians and health officers. wever, often associated distinctly inpairs. On solid media the cocci occur frequently as diplococci, butusually they grow in longer or shorter chains. Certain cocci fre-(|U(ntly exceed their fellows greatly in size, especially in old cul-24 370 PA THOGEXIC MICRO-ORGAXISMS. tiires, when this may be considered to be the result of invohitionforms. These were formerly called by Hueppe arthrospores. Somevarieties have distinct capsules when growing in the blood and inblood
. Pathogenic micro-organisms, including bacteria and Protozoa; a practical manual for students, physicians and health officers. wever, often associated distinctly inpairs. On solid media the cocci occur frequently as diplococci, butusually they grow in longer or shorter chains. Certain cocci fre-(|U(ntly exceed their fellows greatly in size, especially in old cul-24 370 PA THOGEXIC MICRO-ORGAXISMS. tiires, when this may be considered to be the result of invohitionforms. These were formerly called by Hueppe arthrospores. Somevarieties have distinct capsules when growing in the blood and inblood-serum media (Hiss). Staining.—They stain readily by aniline colors and the pyogenicvarieties positively by Grams method. Some varieties, mostlysaprophytic, growing in short chains are negative to Grams stain. Biology.—^Streptococci grow readily in various liquid and solidculture media. The most favorable temperature for their develop-ment is from 30° to 37° C, but they multiply rather freely at ordi- FiG. 121 Fig. 122 ft* ^ ^f Streptococci from solidified serum cultureappearing mostly in diplococci. ^treptococci in throat exudate smeared oncover-glass. X 1000 dianaeters nary room temperature—18° to 20° C. They are facultative anae-robes, growing both in the presence and absence of oxygen. Cultivation.—Growth on Gelatin.—Tubes of gelatin which have beeninoculated with streptococci by puncture with platinum needle showon the surface no growth beyond the point of entrance. In the depthof the gelatin on the second or third day a distinct, tiny band appears,with granular edges or made up of granules. These granules maybe very fine or fairly coarse. They are nearly translucent, with awhitish, yellowish, or brownish tinge. With characteristic culturesthe gelatin is 7iot liquefied. Growth on Agar. — On agar plates the colonies are visible aftertwelve to thirty hours growth at 37° C., and present a beautiful ap-pearance when magnified sufficiently to s
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