39O L. H. HYMAN. 







('19) found that small individuals of Planaria dorotocephala 

 produce more carbon dioxide per unit weight than large ones, 

 and this experiment is now regularly performed as a class experi- 

 ment. Allen ('19) has shown that the rate of oxygen consump- 

 tion of Planaria agilis per unit weight is greater the smaller the 

 animals, and reports that Miss Wolf working in the same labora- 

 tory found the same to be true for the leech, crayfish, branchipus, 

 may-fly nymph, and stone-fly nymph. It is also the case with 

 dragon-fly nymphs, as shown by Mr. G. C. Hawk in this labora- 

 tory. According to Morgulis ('15), the oxygen consumed per 

 gram per hour by flounders is in general greater for small than 

 for large animals. Tashiro and Adams ('14) note that the 

 carbon-dioxide production of the ganglionic cord of the heart of 

 Limnlus is relatively greater in small than in large cords. Nico- 

 las ('18) found that the young leaves and stems of plants give off 

 from 3! to 7 times as much carbon-dioxide per gram per hour 

 as old leaves and stems from the same branch. 



A considerable amount of labor has been devoted to this 

 problem in the case of mammals, especially man. Rubner 

 originally maintained that warm-blooded animals of different 

 sizes produce the same amount of heat per unit surface, but 

 subsequent investigations have shown that this point of view 

 is erroneous. Thus Magnus-Levy and Falk ('99) clearly showed 

 that the oxygen consumption and carbon-dioxide production is 

 highest in children and decreases with age, as measured either 

 per unit weight or per unit surface. If individuals of the same 

 size and weight but of different ages are compared, the younger 

 ones respire the faster. The authors conclude that the proto- 

 plasm of children has a definitely higher rate of respiration per 

 unit weight than that of mature individuals. References to 

 other work supporting these conclusions will be found in their 

 paper. Recently Du Bois ('16) and Gephart and Du Bois ('16) 

 have verified this earlier work. The graphs and tables pre- 

 sented by Du Bois show that the heat production as measured 

 per kilogram of weight is highest in infants and decreases grad- 

 ually; as measured per unit of surface, it is low in infants, 

 increases rapidly during the first year, reaches a maximum 

 between the ages of I and 6, falls rapidly to 20, and thereafter 



