328 



PHYSIOLOGICAL REGULATIONS 



the dog) in figure 159. Total energy is measured in place of total 

 substance; the two are equivalent, since no qualitative choice of 

 foods is allowed. Intake, which is controlled by the experimenter, 

 varies from 2 to 5 Cal./kg. hr., without much discrepancy between it 

 and output. Outside these rough limits, in low intakes the output 

 is at a constant minimal rate ; while in high intakes, the dog con- 

 tinues to eat all the food given, and retains a considerable propor- 

 tion instead of expending it. In contrast to water, storage of com- 

 ponent is a prominent feature, modification of output playing a 

 smaller but also significant part in adjustment. 



O 



O 



u 



F 



4- 



012345678 



Total Enerqy Intake— Caly1\q. hr 



Fig. 159. Rate of total energy output in relation to rate of total energy intake. 

 Meat was given in varying amounts to a dog kept in a calorimeter at 20° to 30° C. Each 

 point represents a period of one day; individual II closed circles, individual III open 

 circles. Along the dash line output VFOuld equal intake. Data of Rubner ( '02, p. 109 

 solid points, p. 115 open points). 



Duration of each allowed rate of intake influences the output. 

 For carbon (fig. 160) the intake and output are proportional to the 

 total substances. During each day that an intake greater than the 

 turnover of former maintenance is fed, the output increases 

 until finally the output becomes equal to the intake. Given time, 

 therefore, a new balance of exchanges is struck, and a new content 

 of total body substance appears to be maintained. This fact ac- 

 counts for much of the confusion prevailing as to how the content of 

 total substance (or of total potential energy) is maintained. Par- 

 ticularly in the dog, there often seems to be a discrepancy between 

 the amount ingested and the amount "required." The answer is 

 that minimal maintenance is a balance, within the accuracy of usual 



