Lectures on the comparative anatomy and physiology of the vertebrate animals : delivered at the Royal College of Surgeons of England, in 1844 and 1846 ... Part 1. Fishes / by Richard Owen.

Date:
1846
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on the comparative anatomy and physiology of the vertebrate animals : delivered at the Royal College of Surgeons of England, in 1844 and 1846 ... Part 1. Fishes / by Richard Owen. 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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    conceivably minute and light ova will be raised with the dust by the first puflT of wind, diffused through the atmosphere, and may there remain long suspended ; forming, perhaps, their share of the particles which we see flickering in the sunbeam, ready to fall into any collection of water, beaten down by every summer shower into the streams or pools which receive or may be formed by such showers, and, by virtue of their tenacity of life, ready to develope themselves wherever they may find the requisite conditions for their existence. The possibility, or, rather, the high probability, that such is the design of the oviparous generation of the Infusoria, and such the common mode of the diffusion of their ova, renders the hypothesis of equivocal generation, which has been so frequently invoked to explain their origin in new-formed natural or artificial infusions, quite gratuitous. If organs of generation might, at first sight, seem superfluous in creatures propagating their kind by gemmation and spontaneous fission, equivocal generation is surely still less required to explain the origin of beings so richly provided with the ordinary and recognised modes of propagation. Many experiments have, however, been detailed, in which adequate precautions appeared to have been taken to prevent the possibility of the entry of fertile germs into the fluid experimented on, after means had been taken to destroy all that it might contain. From these experiments, the mere access of atmospheric air, light, and heat to the infusions has been deemed to include all the conditions required for the primary form- ation of animal or of vegetable organisms. The results in favour of such a view are, however, explicable by supposing that due pre- cautions had not been adopted at the beginning of the experiment to exclude every animal or germ capable of development in the infusion, or to gain satisfactory assurance that the air subsequently admitted contained nothing of the kind. The only experiment in which these diflaculties appear to have been fully overcome, is that in which the requisite apparatus was conceived by Professor Schulze of Berlin. He filled a glass flask half full of distilled water, in Avhich were mixed various animal and vegetable substances: he then closed it with a good eork, through which were passed two glass tubes, bent at right angles, the whole being air-tight: it was next placed in a sand bath, and heated until the water boiled violently. While the watery vapour was escaping by the glass tubes, the Professor fastened at each end an apparatus which chemists employ for collecting carbonic acid : that at the one end was filled with concentrated sulphuric acid, and the other with a solution of potash. By means of the boiling heat, it is to be presumed that every thing living and all germs in the flask or in the tubes were destroyed ; whilst all access Avas cut off by the