. Pathogenic microoÌrganisms; a practical manual for students, physicians, and health officers . .m^- \- 21 SPORES 22 ^^ ^ES25 CSZl r F G IRREGULAR FORMS IN OLD CULTURES (INVOLUTION FORMS] («^^* A. W. WILLIAMS, DEL. O 9^ . 27 «â¢-» % tP 4 4 â â *⢠BACTERIA 33 Structure of Bacterial CeUs.âWhen examined living in a hangingorop (see p. 71) under the microscope, bacteria appear usually as color-less retractive bodies with or without spores or other more highlyretractive areas. It is only by the use of stains that we are able tosee more of their structure. Capsule.âSpecial staining methods (see
. Pathogenic microoÌrganisms; a practical manual for students, physicians, and health officers . .m^- \- 21 SPORES 22 ^^ ^ES25 CSZl r F G IRREGULAR FORMS IN OLD CULTURES (INVOLUTION FORMS] («^^* A. W. WILLIAMS, DEL. O 9^ . 27 «â¢-» % tP 4 4 â â *⢠BACTERIA 33 Structure of Bacterial CeUs.âWhen examined living in a hangingorop (see p. 71) under the microscope, bacteria appear usually as color-less retractive bodies with or without spores or other more highlyretractive areas. It is only by the use of stains that we are able tosee more of their structure. Capsule.âSpecial staining methods (see p. 78) show that manybacteria (some in\estigators say all) under certain conditions possessa capsule (PMe III, Figs. 14-16), a gelatinous envelope which is sup-posed to be formed from the outer layer of the cell membrane. Somebacteria easily develop a much thicker capsule than others. Suchforms are known as capsule bacteria. These generally produce aslimy growth on cultivation (e. g., B. mucosm).. Fig. 1.âBacillus pneumonisE (B. mucosus) stained for capsule by Huntoous method X about 9nn. rTTuntnon ^ X about 900. (Huntoon.) Capsules develop best in animal tissues. In cultures, with a fewexceptions, they require for their development special albuminousculture media, such as milk, blood serum, bronchial mucus, etc. Inordinary nutrient media or on potatoes the capsule may be visiblein the first culture generations when grown from the body, but usuallyit shows very indistinctly, if at all. The capsule is distinguished bya diminished power of staining with ordinary aniline dyes; therefore,unless special staining methods are used, the bacteria may appear tobe lying in a clear unstained area. With certain dyes the inner por-tion of the capsule stains, giving the bacteria an apparent greaterdiameter. The demonstration of the capsule is often of help in difPer-entiating between different but closely related bacteria; e. g., someforms of streptococcus and pneumococcus. C
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