. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. REACTIONS TO VARIATIONS IN SALINITY. 179 about as much oxygen at the beginning of the experiment as did the sea water from which the fish were captured. The solutions were agitated frequently and it is not likely that any marked decrease in the oxygen content occurred during the experiment. Moreover Powers (22) has noted that the oxygen content of the normal medium in which fresh water or marine fish live can be decreased to a low level (between cc. per liter) before the fish will exhibit oxygen want. That anoxemia w
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. REACTIONS TO VARIATIONS IN SALINITY. 179 about as much oxygen at the beginning of the experiment as did the sea water from which the fish were captured. The solutions were agitated frequently and it is not likely that any marked decrease in the oxygen content occurred during the experiment. Moreover Powers (22) has noted that the oxygen content of the normal medium in which fresh water or marine fish live can be decreased to a low level (between cc. per liter) before the fish will exhibit oxygen want. That anoxemia was an important factor in the death of the fish placed in experimental solutions has been the conclusion of many investigators. Indeed, it has been shown by Backman (23) that if the sea water in which dogfish live, with A = • ° is diluted to A = - °, fifteen minutes after being placed in this solution, the tension of oxygen in the blood is diminished from to per cent. This anoxemia was believed to be a result of injury to the gill membranes and to the change in the water and salt content of the blood with the attendant change in size and the destruction of the blood corpuscles, thus decreasing the gas carrying power of the blood. However, if fish were dying from asphyxia due to an injury of the gill membranes while the irritability of the respiratory center remained normal, hyperemia and dyspnoea might be expected. They did not occur in Squalus sucklii. The changes observed correspond more with those to be expected from a depression of the respiratory center. As a result of this investigation and the contributions to this problem made by others, the author is inclined to explain the death of fish in media having an abnormal salinity to a progressive depression of the respiratory center. Although a change in the composition of the surrounding medium frequently alters the permeability of the limiting membranes of the body, the changes in the osmotic pressure o
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
