A manual of bacteriology, clinical and applied / by R. Tanner Hewlett.

Date:
1914
Catalogue details

Licence: In copyright

Credit: A manual of bacteriology, clinical and applied / by R. Tanner Hewlett. 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.

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    beings. Weismann based his theory of heredity on the fundamental conception of the immortality of these unicellular organisms. Excluding accidents, they are immortal—they reproduce themselves by a process of simple division, an individual dividing, and two daughter forms taking the place of the original parent one, and although the parent has disappeared yet there has been no death, no dissolution ; its protoplasm or living material is still existent in its progeny and is immortal, since this process of reproduction apparently may go on indefinitely. Moreover, the study of the mutability and possible trans- formation of species of micro-organisms is likely to throw light on the theory of evolution. Organisms such as bacteria multiply so rapidly that fifty or sixty generations may develop in thirty hours, a number which would take years to attain if even the most rapid breeder among mammals were the subject of experiment, and as they occur in vast numbers the opportunity for variation is extensive. These are some of the relations which micro- organisms have with general biology. In what may be termed the economy of nature micro- organisms are all-important ; without them there would be no putrefaction, no decay, and the dead remains of animal and vegetable life would accumulate and encumber the earth, which would become barren for the want of the organic matter originally derived from it, but of which there was no return. In fact the higher plants, and indirectly, therefore, animals also, are dependent for their existence upon the presence of bacteria in the soil, which break up and render assimilable complex substances used as manures. The question of life, animal and vegetable, without bacterial activity is an important and interesting one. It would seem from the experiments of Duclaux1 that the 1 Comp. Rendn t. 100, p. 66.