Pathogenic micro-organisms : including bacteria and Protozoa; a practical manual for students, physicians and health officers / by William Hallock Park ; assisted by Anna W. Williams.
- William Hallock Park
- Date:
- 1908
Licence: In copyright
Credit: Pathogenic micro-organisms : including bacteria and Protozoa; a practical manual for students, physicians and health officers / by William Hallock Park ; assisted by Anna W. Williams. Source: Wellcome Collection.
31/712 page 13
![is mucli simpler than in the ease of the cocci. We may thus have bacilli as isolated cells, as pairs, diplohacilli, or as longer or shorter chains, strcptohacilli. 3. Spiral Form, or Spirillum.—The members of the third mor- phoiogical gronp are spiral in shape, or other segments of a spiral. Here,' too, we have large and small, slender and thick spirals, ihe twisting of the long axis, which here lies in. two planes, is the chief characteristic of this gronp of bacteria. ^ Under normal conditions the twisting is nniform thronghont the entire length of the cell, ihe spirilla, like the bacilli, divide only in one direction. A single cell, a pair, or tbe union of two or more elements may thus present the Fig. 10 Fig. 11 appearance of a short segment of a spiral or a comma-shaped form, an S-shaped form, or a complete spiral or corkscrew-like form (Figs. 8, 9, 10 and 11). The determination of morphologic characters for the description of bacteria should always be made from fully developed cultures; those which are too young may present, as already noted, immature forms, due to ra]iid multiplication, while in old cultures altered or degenerated forms may be observed. When gi’own upon different media, variations, especially in size, may sometimes be observed. Tliese differences sbould always be described, together with a note of the media upon ivhich they were develoyied and a statement as to whether such variation is a marked feature of the species under consideration. The conditions of temiierature and of nutrition which favor growth are very various for different species, so that no fixed temperature, medium, or age of growth can be regarded as a]>plicable to all species. !Mor])hologic descriptions should always be accompanied by a defi- nite statement of the age of the growth, the medinm from which it was obtained, and the tem])crature at which it was developed. Structure of Bacterial Cells.—When examined in water under the microsco])o bacteria ap]>ear merely as colorless refractile bodies with or without spores or more highly refractive areas. It is only by the](https://iiif.wellcomecollection.org/image/b28137541_0031.jp2/full/800%2C/0/default.jpg)
