The Food-Vacuole in the Peritricha, With Special Reference to the Hydrogen-Ion Concentration of Its Content and of the Cytoplasm

THE FOOD-VACUOLE INPARAMECIUM

“…I could not, however, make out any details as to their attachment or their length. This indicates that the index of refraction of these fibers is very nearly the same as that of the cytoplasm in which they are imbedded and that in this respect they differ from those found in the Peritricha for in these organisms they can readily be seen in the living state (Mast, 1944;Mast and Bowen, 1944).…”

“…Some of the observations were made on specimens which had been greatly compressed under the cover-glass, others on specimens stained with various vital dyes and still others on specimens in various stages of inanition. All were made with the highest grades of optical and illuminating systems (Mast and Bowen, 1944).…”

“…The membrane around the food-vacuole is therefore pervious to water, and the loss of water, which causes the vacuole to decrease in size, is doubtless due to excessive external osmotic concentration and inward pressure of the stretched vacuolar membrane (Mast and Bowen, 1944).…”

“…The evidence in hand obviously throws but little light on the processes involved in the initiation of the separation of the food-vacuole from the pharynx in paramecia, and this is also true for other forms. Mast and Bowen (1944) considered this problem theoretically in reference to the Peritricha and reached the following conclusions: "It is highly probable that waves start at fairly definite intervals in the pharyngeal ring and pass simultaneously down all the esophageal fibers and that each of these sets of waves initiates a constriction in the esophageal sac, if it contains sufficient fluid to make a constriction possible. If this is true, the size of the vacuole is correlated with the rate at which the fluid is forced into the esophageal sac by the cilia in the pharynx and the rate at which it leaves this sac by osmosis.…”

The Active Transport of Water in Living Systems

“…Picken (1936) measured the cytoplasmic vapour pressure of the heterotrichous ciliate Spirostomum ambiguum by means of a thermopile and found it to correspond to 0.15 % NaCl, or 0.05 osmolar, of the same order as the figure of 0.077 osmolar given by Gelfan for S. teres. Mast & Bowen (1944) determined the difference in osmotic pressure between the intracellular fluid of Vorticella and its surroundings by the lowest concentration of lactose which caused the organism to shrink; this was 0 . 0 1 2 5~.…”