. The comparative physiology of respiratory mechanisms. Respiration. 40 RESPIRATORY MECHANISMS system is further enhanced by arrangements which, in spite of alternating inspiratory and expiratory movements, produce a continuous flow of water through the branchial system (van. Fig. 16. Diagram of two gill filaments, (van Dam.) Dam). Inspiration takes place by a dilatation of the mouth and branchial cavity with closed opercula and opening of the mouth. Part of the inspired water remains in the mouth, but part is passed through the gills to the branchial cavity. During expiration the mouth is clo
. The comparative physiology of respiratory mechanisms. Respiration. 40 RESPIRATORY MECHANISMS system is further enhanced by arrangements which, in spite of alternating inspiratory and expiratory movements, produce a continuous flow of water through the branchial system (van. Fig. 16. Diagram of two gill filaments, (van Dam.) Dam). Inspiration takes place by a dilatation of the mouth and branchial cavity with closed opercula and opening of the mouth. Part of the inspired water remains in the mouth, but part is passed through the gills to the branchial cavity. During expiration the mouth is closed, the opercula opened and the water contained in the mouth passed out through the gills. Van Dam shows by an ingenious experiment that the pressure in the mouth of a trout is in both phases of the respiration higher than in the gill cavity. The efficiency of the mechanism is well shown by the very high coefficient of utilization reached by fishes. Van Dam, who made very reliable measurements of ventilation and utilization both on the eel (Anguilla vulgaris) and a trout (Salmo shasta), finds in both species a normal utilization close on 80%. Low oxygen concentrations and CO2 tensions up to 7 or 10 mm increase the ventilation and may somewhat reduce the utilization. The ventilation may be increased up to fivefold when the oxygen content of the water is below 4 ml/1. This causes a decrease in utilization, but an increase in metabolism amounting in the eel to 40% and in the trout even to 70%. Van Dam gives very good reasons for the conclusion that this. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Krogh, August, 1874-1949. Philadelphia, University of Pennsylvania press
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