Bacteria, the smallest of living organisms / by Ferdinand Cohn ; translated by Charles S. Dolley.

  • Ferdinand Cohn
Date:
1881
Catalogue details

Licence: Public Domain Mark

Credit: Bacteria, the smallest of living organisms / by Ferdinand Cohn ; translated by Charles S. Dolley. 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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    Probably there are more than fifty milliards of cells wlricli form such a mass in the course of one day from one single grain. We as yet know of no other mode of increase in the bacteria beside bi-partition. Generation of eggs and spores, as is found of all other animals and plants, has not yet been observed in these simple.st forms.* After division the halves of the bacteria separate, and wander about as independent organisms, or remain connected chain-like, and form longer or shorter threads ; in other cases whole generations remain congregated in colonies, united in nests or balls, or collected together in heaps, which appear to the naked eye as colorless or perhaps colored gelatin- ous or sliniy masses,f as little white flakes or threads swimming in the water, or settle as flakes to the bottom of the fluid. Bacteria belong to the most wide-spread of organisms; we may say they are omni])resent; they never fail either in air or water; they attach themselves to the surface of all firm bodies, but develop in masses only where decomposition, corruption, fennentation or putrefaction are present. If we place a piece of flesh, a pea or other animal or vegetable material in water, it will become, earlier or later, thick, and then milky. It loses * Since writing the above the author has satisfied himself not only of the existence of spores, hut of veritable sporangia, and has by experiment found that the spores of Bacillm will for several days withstand a temperature of 80 (176® Fah.), still retaining the power of germination, while, along with Frisch, he has proven that gradual freezing does not destroy them, develop- ment having occurred after exposure to a temperature of —87 (—123 Fah.). He states that “ reproduction by means of spores is only made under the in- fluence of free access of air.” Bacteria spores, besides their ability of re- sisting vicissitudes of*temperature, will withstand complete dessication; and Magnin says: “ These spores are the point of departure of epidemic foci, and their extreme lightness explains how readily they are disseminated by the wind. It has been shown from the experiments of Cohn and Miguel that the atmosphere contains very few adult bacteria; while Cohn again proves that these germs are of so small a diameter that they pass through all filters.” f “ Cohn explains the origin of the gelatinous substance in which the ■ bacteria are included as being produced by a thickening or jellification of the cell membrane; but a more plausible view is that it is produced by a secretion from their protopla.sm. It is commonly the spherical bacteria {Micrococcus) and the microbacteria {Bacterium) which are found in this state. The bacteria are of course motionless in the Zoiigloca on account of the intermediar}' glairy sub.stance.”—Magnin. The filliform bacteria and the spirilla, according to Cohn, are never found in gelatinous masses, but may be found in active swarms.
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