THE EFFECT OF LOW OXYGEN TENSION ON THE PULSATIONS OF THE ISOLATED HOLOTHURIAN CLOACA

Abstract

1. An isolated muscle strip from the cloaca of Stichopus moebii Semper and a ring of muscle from the cloaca of Cucumaria frondosa were used in sea water as rhythmically beating preparations. 2. In a continuous flow of sea water the contractions (Stichopus) were nearly uniform in rate and amplitude over a period of several hours, but a gradual decrease in both finally occurred. 3. In a limited volume of sea water (100 cc.) the amplitude (Stichopus) began to increase after three hours and a distinct periodicity of the regular rhythm developed. In the case of the cloacal ring of Cucumaria beating in 25 or 30 cc. of sea water, periodicity appeared in 50 minutes on the average. 4. In boiled sea water the strip (Stichopus) ceased beating in from three to five minutes, but partial recovery took place if the water was aerated within three minutes. If the carbon dioxide was replaced in the boiled sea water, cessation of beat occurred as before. In 25 or 30 cc. of boiled sea water the ring of cloacal muscle from Cucumaria developed periodicity in 25 minutes on the average. 5. A moderate excess of carbon dioxide in sea water (pH 7.0) did not bring on augmentation nor produce periodicity. 6. In boiled sea water of various degrees of aeration the augmentation of amplitude and the periodicity appeared sooner than in unboiled sea water. When little oxygen was present both phenomena appeared almost immediately, while the pH of the surrounding fluid was unchanged. 7. When potassium cyanide was added to the sea water an increase in amplitude and tone occurred and periodicity appeared. 8. Evidence from the literature is cited supporting the view that decreased oxygen tension results at first in increased activity of muscular and nervous tissues. This view is further supported by the evidence presented in this paper.²