The Relation of the Carbon Dioxide Tension of the Water to the Hemoglobin Content of the Blood, the Gaseous Content of the Swim-Bladder, and the Ability of the Fish to Extract Oxygen from the Water at Low Oxygen Tensions
Date of Award
Master of Science
Edwin B. Powers
Probably in no field of biology is reasoning from analogy depended upon more than it is in human physiology to answer the questions which constantly arise in the mind of the investigator. This is particularly true of that phase of respiration which attempts to explain the apparent secretion of oxygen into the blood at low oxygen tensions. The secretion theory has found much favor with certain physiologists and in briefly presenting their case in his Text Book of General Physiology (1932) Mitchell has said as a point in its favor, "Glands of the swim bladders of many species of fishes secrete oxygen under high pressure into the swim bladders". In a full discussion of this question Powers (1932) has shown that gases are not secreted into the swim-bladder in the true sense of that term, and that, "The secretion of oxygen into the lungs might still be an open question. But, on the other hand, the deposition of gases into the swim-bladder cannot be used as an illustration of a mechanism by which this is accomplished." Thus in this case, as with many other physiological problems, it will be necessary to extend our knowledge of the physiological process in other forms of animal life if conclusions based upon them are to be accepted as valid.
It has been shown by Powers and Hickman (1932) that the oxygen dissociation curve for the blood of certain fishes shows two depressions as the carbon dioxide tension to which the blood is exposed increases. The first depression they attribute to the lack of affinity of hemoglobin for oxygen at its isoelectric point. This is shortly followed by a rise which continues until the carbon dioxide tension is about 1.2% of an atmosphere, after which there is a second depression. It is suggested by Powers and Hickman that, "The second depression is perhaps due to the actual breaking down of hemoglobin into its intermediate products."
The series of experiments which have been performed were designed to investigate the changes which take place in the swim-bladder gas and the blood of fish when exposed to small variations in carbon dioxide tension. It was thus hoped to learn something of the physiological activities of the fish when in a habitat whose carbon dioxide tension is close to the isoelectric point of the blood.
Wingo, Spurgeon Meek, "The Relation of the Carbon Dioxide Tension of the Water to the Hemoglobin Content of the Blood, the Gaseous Content of the Swim-Bladder, and the Ability of the Fish to Extract Oxygen from the Water at Low Oxygen Tensions. " Master's Thesis, University of Tennessee, 1936.