. The comparative physiology of respiratory mechanisms. Respiration. 36 RESPIRATORY MECHANISMS depending upon the temperature and the oxygen content of the water. At low oxygen contents (2 ml/1) the ventilation may become continuous, but at very low ( ml/1) it may stop almost completely. The utilization of the dissolved oxygen is variable, but may reach the high value of 70%. Arenicola was studied by van Dam, who found that the animal would respire in a normal manner when enclosed in a U-shaped glass tube as shown in Fig. 11. It is characteristic. Fig. 11. Determination of ventilation volum
. The comparative physiology of respiratory mechanisms. Respiration. 36 RESPIRATORY MECHANISMS depending upon the temperature and the oxygen content of the water. At low oxygen contents (2 ml/1) the ventilation may become continuous, but at very low ( ml/1) it may stop almost completely. The utilization of the dissolved oxygen is variable, but may reach the high value of 70%. Arenicola was studied by van Dam, who found that the animal would respire in a normal manner when enclosed in a U-shaped glass tube as shown in Fig. 11. It is characteristic. Fig. 11. Determination of ventilation volume in Arenicola. (van Dam.) also for Arenicola, that breathing is intermittent. In one typical case there were pauses of about 20 minutes (at 20°C) and activity periods of about 10 minutes, during which about 90 ml water were passed through the tube. Thirty to 50% of the oxygen in this water was normally utilized by the ani- mal, and it is a very interesting fact that the utilization per- centage remained about the same, also when the water con- tained only 5% of the normal amount of oxygen or when the animal breathed normal water after a prolonged exposure to low oxygen. In the decapod Crustacea the gill cavities below the carapace on both sides of the body are ventilated by the regular beating. 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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