The division and post-fission movements of bacilli when grown on solid media / by G.S. Graham-Smith.

  • Graham-Smith, G. S. (George Stuart), 1875-1950.
Date:
1910
Catalogue details

Licence: In copyright

Credit: The division and post-fission movements of bacilli when grown on solid media / by G.S. Graham-Smith. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    clean field, should be chosen. After a little experience it is generally easy to decide whether a given organism is going to divide or not. An organism which is likely to divide is usually larger and better defined and more opaque than one which is apparently dead. Moreover in some species the living healthy bacterium, if carefully watched, shows slight changes in outline at intervals, suggesting some plasticity in the bacterial walls. 5. Method of recording the observations. After the preparation had been placed on the stage of the microscope and a suitable organism focussed, the time was recorded and the organism drawn and labelled 1. The specimen was then carefully watched, and any changes noted. Usually a long period of time, up to an hour or more, elapses before any change occurs. In most species the first important change to be seen is an increase in length, accompanied by a slight bending. Later a segmentation interval appears in the middle of the organism, dividing it into two more or less equal portions. These two parts are labelled 11 and 12 respectively in the drawings. After this division, or fission, the behaviour of the organism differs according to the group to which it belongs, but in all cases various movements take place to which the term “ post-fission movements ” was applied by Hill. The two new organisms (11 and 12) grow and again divide, and ultimately numerous organisms are produced and form a colony. For the purposes of identification the organisms arising from the division of 11 were labelled 111 and 112, and those from 12 were labelled 121 and 122 and so on1. The time at which each division or other well marked change occurred was also noted. 6. Photographic records. Photographic records were also obtained, showing the mode of multi- plication of a typical member of each group. When a suitable bacterium had been found the microscope was removed from the thermostat and clamped in a horizontal position on a Zeiss camera. Illumination was obtained by means of limelight or a mercury vapour lamp, and the organism focussed on a clear glass screen. The magnification varied 1 The genealogical relationships of the new cells are indicated by Hill’s (1901, p. 84) modification of Biekard’s (1901) system for culture record. The modification consists merely in omitting the decimal point and all figures to the left of the point.