Abstract
The influence of carbon dioxide upon the respiration of the lateral line nerve of the smooth and spiny dogfish has been studied by the tonometric method. Fifteen cc. tonometers which contained besides the nerves one-tenth of a cc. of isotonic solution were placed in a water bath, the temperature of which varied from 20.5 to 23.7°C. in the different experiments. The gas mixture present in the tonometers was analyzed at the beginning and at the end of each experiment on a modified Haldane-Henderson analyzer. The measurement was begun 2 to 3 hours after the removal of the nerves and lasted for 4 or 5 hours. Eight or more hours after the isolation of dogfish nerves the rate of oxygen consumption rapidly increases.
The tonometric method has been checked by burning ethyl alcohol in the tonometers and determining the respiratory quotient. These quotients vary from 0.630 to 0.678 with an average of 0.655.
Ten control experiments showed that the maximum difference in the rate of respiration of matched nerves was 16%. Forty-five experiments were carried out on nerves in air-oxygen gas mixtures. The rate of oxygen consumption varied from 25.1 to 157.0 cu. mm. per gm. of fresh weight per hour, depending upon the size of the nerve. The average was 64.1 cu. mm. The rate of carbon dioxide production fluctuated between 17.3 and 176.0 cu. mm. per gm. per hour with an average of 59.2. The apparent respiratory quotients averaged 0.92.
Calculation of the oxygen tension necessary to supply these nerves by Fenn's 1 or Gerard's 2 formula indicated that in all cases sufficient oxygen was present to prevent asphyxia. This has been tested directly in a few experiments.
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