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Journal of Experimental Biology 15,143-151 (1938)
Published by Company of Biologists 1938

The Physiology Of Contractile Vacuoles : III. The Water Balance Of Fresh-Water Peritricha

J. A. KITCHING ¹

¹ Departments of Zoology of Birkbeck College, London, and of the University, Edinburgh

1. The rate of output of fluid from the contractile vacuoles of fresh-water peritrich ciliates was reduced in solutions of sulphide of concentration not less than M/1000. This effect was reversible.

2. Cyanide depressed the rate of vacuolar output in a concentration of M/100,000, but was more effective in higher concentrations (M/1000). In cyanide solutions there was (a) either a severe initial check or a temporary stoppage of the vacuole, and then later (b) a partial recovery of the rate of output to a value which was still much below the normal. During the initial check the body swelled.

3. Return of the organism from cyanide solution to tap water was followed by a sharp increase in the rate of vacuolar output to an abnormally high value. The body then shrank gradually to its normal size, and the rate of output also fell slowly to normal.

4. The swelling of the body which followed treatment of the organism with cyanide could be exactly counteracted by the addition of sucrose to the outside medium in a 0.05 M concentration.

5. It is concluded that the normal difference of osmotic pressure across the body surface is equivalent to that of a 0.05 M sucrose solution, and that this difference is maintained by the contractile vacuole.

6. The permeability of the body surface to water is estimated as 0.125-0.25 cubic micra per square micron per atmosphere per minute.