RELATION OF OXYGEN TENSION AND ACTIVITY OF THE NERVOUS SYSTEM TO METABOLISM IN CASSIOPEA.* Henze (1910a) observed that sea-anemones use less oxygen when less is present in the sea-water, but interpreted this as due to the time required for diffusion into the animal. That is to say, he supposed that all of the cells were not supplied with oxygen when there was little in the sea-water. If oxygen was entirely absent in some of the cells, the decreased oxidation may have been merely the expression of the lesser number of cells taking part in the metabolism. Burrows showed that tissue cells require a certain oxygen tension for growth. Verzar showed that the cat's heart is slowed by reducing the oxygen, and Loeb and Wasteneys found that the heart-beat of Fundulus embryos may be slowed by reducing the oxygen. The growth of Fundulus may be sus pended by lack of oxygen and may be slowed by diminishing the oxygen. Johansen and Krogh found that plaice-fish eggs develop slower when the oxygen tension is reduced.
The calorimeter consisted of either an 850 c.c. or a 900 c.c. Dewar flask (thermos bottle) inclosed in an air-tight container, which was immersed in water that was maintained at the same temperature as the water in the flask, within 0.003°. The technical difficulties were met as follows: Two Beckmann thermometers were adjusted and com pared over the range of temperatures of the experiments and fitted with reading-lenses to estimate down to 0.001°. A large tank of sea water was brought to 30° (which was about the temperature of the air) and its pH and and content determined. A cassiopea was in troduced into some of this sea-water that was dipped out into a jar. The thermos bottle, stopper, and thermometers were immersed in the large tank until they reached the temperature of the water. The cassiopea was transferred to the thermos bottle and a perforated cork stopper was inserted, with the exclusion of air-bubbles. One Beckmann thermometer was inserted through the perforation in the stopper and the other suspended in the tank, near the middle of the thermos bottle. A small hole, remaining in the stopper for exit of displaced water, was closed with wax. The pulsations of the cassiopea stirred the water inside the thermos bottle, and the water in the tank was mechanically stirred and was kept at the same temperature as that inside the thermos bottle by additions of small portions of warmer or colder water as required. The light was excluded by the silvering and coverings
of the thermos bottle, but in some experiments in which a 900 c.c. glass jar with ground-glass cover was used in place of the thermos bottle, the light could be excluded by darkening the tank, so as to prevent photosynthesis in the symbiotic plant cells. Time was measured by means of a stop-watch and a clock. The same cassiopea was used in a series of experiments.
The oxygen in the sea-water was determined by the Winkler method, which can be corrected for the small error due to a slight amount of organic matter given out by Cassiopea, and it was thought impracticable to use the complicated method of Shutzenberger and Risler (Henze, 1910b). A 250 c.c. glass-stoppered bottle was weighed empty and full of distilled water at a known temperature, in order to standardize its volume. It was fitted with a double-bored rubber stopper and a long and a short glass tube with rubber connections. The bottle was filled with mercury and the long glass tube was sucked full of the water to be analyzed and the stopper inserted. By inverting the bottle the sea-water was siphoned into it, when the rubber stopper was removed and the glass stopper inserted. The glass stopper was lifted and 1 c.c. of alkaline KI solution and 1 c.c. of 40 per cent MnCl2 solution intro duced (correction being made for this in the 02 calculation) and the stopper was inserted. Colloidal membranes formed about the drops of alkali and violent shaking was necessary to break them. After the precipitate had settled, 2 c.c. of concentrated HC1 were added and the stopper inserted and the bottle shaken. Its contents were transferred to a flask and titrated with 0.01 N sodium thiosulphate solution until the yellow color disappeared; then starch solution was added and the titration continued until the blue color disappeared; then the water was poured into the bottle and back into the flask and titrated until the blue color disappeared. The calculation was as follows: 0.056 X c.c. thiosulphate capacity of bottle-2 = c.c. of oxygen per liter of sea-water and this quotient multiplied by 0.9 equals cubic centimeters of oxygen in calorimeter (on the assumption that the concentration of oxygen in the cassiopea was the same as that in the sea-water).