SOME EFFECTS OF HIGH PRESSURE ON DEVELOPING MARINE FORMS

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Abstract
Hydrostatic pressure of as much as 1900 pounds per square inch applied to living eggs of the Fundulus causes no evident changes in the cell constituents. The rate of cell division of Fundulus eggs was slowed by maintaining them under pressures of 1300 to 1900 pounds for periods ranging from 30 minutes to three hours. In the pressure samples a few instances appeared of abnormal forms of development. The automaticity of the heart in young embryos becomes slowed by pressure and apparently may be abolished if the compression is maintained but returns within a few minutes following release of the pressure. In ten experiments an average decrease of 9.9 per cent in the heart rhythm under pressure was present within an interval of two minutes. The embryonic heart under pressure develops arrhythmia, types of local block, and isolated fibrillary activity. The action of pressure in slowing the heart rate does not depend on the presence of inhibitory nerves to this organ, since compression produces a slower rhythm of (a) hearts from older embryos that have been dissected free of all extrinsic nerve connections; and (b) hearts of young embryos that have no intrinsic nerves developed. The bearing of viscosity and ionic changes produced by pressure are considered in relation to the decrease in the rate of cell division and the automaticity of the embryonic heart.

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