A manual of bacteriology / by Herbert U. Williams.

Date:
1901
Catalogue details

Licence: In copyright

Credit: A manual of bacteriology / by Herbert U. Williams. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    115/304 (page 105)
    able influences of all sorts than are the fully developed bacteria. Spores resist drying, light, heat and chemical agents to a remarkable degree, at times. Anthrax spores are said to have been found which could withstand steam for twelve minutes, i-iooo mercuric chlo- ride for nearly three days, or 5 per cent, carbolic acid for more than forty days. The greatest resistance is displayed by the spores of some of the saprophytic bacteria, particu- larly those of hay and potato, which are sometimes not destroyed by several hours of steaming; and bacteria are said to have been obtained from the soil which resisted 100° C. for sixteen hours. When cultivated at a tempera- ture as high as 42° C. the anthrax bacillus becomes inca- pable of forming spores. Spores themselves do not mul- tiply, nor do they manifest any activity. Spores may be located at the center of the bacillus, or nearly at one end, when the end of the bacillus is likely to enlarge, making a form having the shape of a drumstick, as takes place with tetanus bacilli (Fig. 68). When a bacillus assumes a spindle shape on account of having the middle part bulged through the formation of a spore it is called a Clostridium. Under favorable conditions the spores germinate, as it is called, and develop to the adult form of the organism. This may be witnessed in hanging-drop preparations. Motility.—Motility is rarely exhibited b}^ micrococci; some bacilli possess it and some do not; while nearly all of the spirilla are motile. The phenomenon is observed in the hanging-drop. The degree of motility is variable, being sometimes slight and sometimes very active. When seen under a high power the little particles taken from a cul- ture of a motile organism may look like a writhing mass of maggots or like tadpoles in a pool. The motility is most active in young cultures. The movement results from the vibration of little processes, ov jlagella (Fig. 46).