. The comparative physiology of respiratory mechanisms. Respiration. 24 RESPIRATORY MECHANISMS stance of the cuticle. Assuming as above A = 100 ml/ kg/hour = 1/600 ml/g/m, r = 1 cm, T = cm, and £> = , we find C0 = 1/4 atm. This would just about allow the necessary quantity of 02 to diffuse in from saturated water, provided the tension just inside the cuticle remained at 0, leaving nothing for the transport by convection. To account for the convection transport we must assume that "blood" arrives at the surface containing a small amount of oxygen at a tension which ma
. The comparative physiology of respiratory mechanisms. Respiration. 24 RESPIRATORY MECHANISMS stance of the cuticle. Assuming as above A = 100 ml/ kg/hour = 1/600 ml/g/m, r = 1 cm, T = cm, and £> = , we find C0 = 1/4 atm. This would just about allow the necessary quantity of 02 to diffuse in from saturated water, provided the tension just inside the cuticle remained at 0, leaving nothing for the transport by convection. To account for the convection transport we must assume that "blood" arrives at the surface containing a small amount of oxygen at a tension which may approach 0. During its passage along the surface it takes up the oxygen passing in. The tension rises in consequence and may—when the condi- tions for diffusion are optimal—approach that on the outside. The mean tension difference must always be definitely lower than the outside tension. It can be found by a complicated integration when the tensions of the blood arriving at and leaving the surface are known. From the formula it is seen that, assuming a constant metab- olism per unit weight, the necessary tension difference is proportional to the radius of the sphere, which would mean a size limit to organisms respiring through the surface. When, however, metabolism is proportional to W2I'S there should be no theoretical size limit, provided the thickness and permea- bility of the cuticle remains the same. In practice, however, these conditions do set limits to the possible size and determine the development of special respiratory 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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