ENVIRONMENT AND REGENERATION 



493 



Relation of size to carbon-dioxide production and regeneration 



It has already been mentioned in connection with earlier 

 experiments (p. 474) that there is a difference between large and 

 small tadpoles in the relation of retardation of regeneration and 

 length of life in various concentrations of bases. Dreyer and 

 Walker ('14) show that in warm-blooded animals of the same 

 species, but of different weights, dosage of drugs must be calcu- 

 lated in relation to body surface rather than weight. They 

 explain this on the ground that "The concentration in the plasma 

 of any given substance administered is dependent on the volume 

 of the circulating blood, which is itself proportional to the body 

 surface in any given species of animal." It is also known that 

 the 'basal heat production' of a warm-blooded animal, which 

 may be defined as the heat produced by the animal when kept 

 at the same temperature as its normal body temperature, at 

 rest and starving, is proportional to body surface for any given 

 species. 



A few experiments were undertaken to see whether any relation- 

 ship could be traced between the body area or body weight of 

 tadpoles and the effects of acids and bases upon regeneration 

 and carbon-dioxide production, which may be regarded as most 

 nearly corresponding to the basal heat production of mammals. 



For the first experiment two tadpoles were used which had been 

 collected at the same time and differed only in size, great care 

 being taken that they should be similar in shape, relative length 

 of tail, etc. After one week of starvation in distilled water they 

 were weighed, and the CO2 production of each was determined 

 for three successive days as follows : 



While the CO2 production per gram of body weight was not the 

 same for the two specimens on any one day, the averages of the 

 three days are practically identical. 



