250 Papers from the Department of Marine Biology, 



It was shown that the metaboUsm of Cassiopea is proportional to its 

 surface and not to its weight (W), but to WK This is due to the fact 

 that the metabohsm is confined to the Uving cells and that these con- 

 stitute a superficial epithelium, whose thickness is about the same in 

 cassiopeas of the range of sizes studied. We might use these results 

 in an attempt to explain the so-called surface-law of warm-blooded 

 animals. Dreyer, Ray, and Walker have shown that the blood-volume 

 and cross-sections of the aorta and trachea are proportional to W* 

 (or surface) . If animals were of the same shape (internally as well as 

 externally), the cross-sections of all organs would be proportional to 

 W% but the blood-volume would be proportional to the weight (W). 

 If the blood-volume is proportional to TF', the whole circulatory system 

 would be nearly proportional to TF% and owing to the close relation 

 between the lungs and the blood the volume of the lungs would be 

 nearly proportional to W'\ The volume of the skin may be propor- 

 tional to W' and the volume of the wall of the alimentary tract nearly 

 so. The nerve, muscle, and glandular tissues are excitable, and hence 

 their metabolism must vary. Variable components may be excluded 

 from basal metabolism by definition, but can not all be eUminated in 

 making measurements. Only the skeleton can be said to have a con- 

 stant metabolism proportional to W, and since the red bone-marrow 

 produces blood (erythrocytes) and this is proportional to the surface, 

 the metabolism of some of the bones may be nearly proportional to the 

 surface. Benedict has shown that great variations from the surface 

 law exist, and hence it may be only accidental. 



The fact that the excitable tissues metabolize more per unit weight 

 in small animals than in large (i. e., proportional to a smaller power of 

 W than unity) is true, not only for warm-blooded animals, but also 

 for cold-blooded animals, to which the teleological principle of the 

 surface law (in relation to heat regulation) does not apply. It seems 

 possible, however, that the chief conditions necessary for the evolution 

 of temperature-regulation in animals were: (1) air breathing; (2) large 

 body size; (3) sensitivity to low temperatures; (4) variation of activity 

 of excitable tissues with size; and (5) epithelial type of architecture, 

 4 and 5 being more characteristic of cold-blooded animals. 



It is hoped that the fact that metabolism varies with O2 tension may 

 explain the increase in metabolism in certain types of acidosis. Lusk 

 and Richie have shown that certain amino acids have a specific 

 dynamic action and Benedict asserts that it has been demonstrated 

 that there is a distinct increase in the basal metabolism with the aci- 

 dosis resulting from the ingestion of a carbohydrate-free diet. It is 

 not assumed that amino acids dissociate enough H ions or neutralize 

 enough base to cause acidosis, and whether there is any relation 

 between the phenomena discussed by Lusk and by Benedict may be 

 open to question, but it seems clear that increased metabolism may 

 accompany acidosis. 



