CELL SIZE AND METABOLIC ACTIVITY IN AMPHIBIA. 



HARVEY M. SMITH, 

 ZOOLOGICAL LABORATORY, UNIVERSITY OF WI-M O\MN. 



I. Introduction 347 



II. Material and Methods 350 



III. Results on tin- I HftVrent Species of Amphibians .o-- 



IV. Controls 



A. Coll 5i 357 



B. Carlx/ii Dioxide Determination 



V. < '(implicating Factors 



.1 . i . II size 



B. Carli'iu Dioxidf Production 



1 . \\' iht of Animal 



2. Starvation . 



3. Daily Variation 



4- Sex ...371 



5. Disease 371 



6. Motihty 



VI. '. n> i. il Comparative Results. . ,.. , 



VII. Summary and Conclusions. . . . 



1 INTKODI'CTION. 



The fact that the mass of a body increases as the cube of the 

 linear dimension, while the surface increases as the square, ha- 

 lon^ been recognized as of im[>ortance in biology. Leuckart 

 i --52) uses it to explain the necessity for increased surface as an 

 organism becomes larger, a necessity which is met in animals by 

 inpushings and the develompent of a distributing system: in 

 plants by outgrowths. Herbert Spencer (1873) says: "Why 

 ha- the indixidual a growth limit? ... In similarly shaped 

 bodies, the masses vary as the cube of the dimensions, when is 

 tin strengths vary as the square of the dimensions." He 

 applies thi- idea to an individual whose height doubles in a 

 given growth prn<>d; the mass has been multiplied by eight, but 

 the strength- o| muscles and bones, being proportional to their 

 cross section, are multiplied by only four. The absorbing surface 

 i- also multiplied by four, while the mass to be nourished l>y the 

 material absorbed is multiplied by eight. It is only a step farther 

 to apply the same idea to cell sixe. The writer was unable to 

 learn who first did this. 



347 



