EDITORIAL. 605 



The devices for determining the carbon dioxid and water vapor 

 removed from the chamber in the ventilating air current remain 

 practically the same as in the former apparatus, but a much simpler 

 appliance is employed for equalizing the air pressure and also a 

 simpler meter for measuring the quantity of air for residual analysis. 

 The new apparatus also embodies improved methods for operating 

 the devices for purifying the air current after it leaves the respira- 

 tion chamber, and for restoring oxygen to it on its return. There 

 has also been a decided improvement made in the apparatus for de- 

 termining the temperature of the air and the copper wall of the 

 chamber, and in the devices for controlling the temperature of the 

 air surroimding the zinc wall. These, however, are technical de- 

 tails which need not be further described. 



During the j)ast winter and spring a series of check tests has been 

 made with the calorimeter which has demonstrated its high efficiency 

 and accuracy, and a variety of experiments have been conducted with 

 a subject. In the latter the scope of the experiments has been 

 greatly enlarged. The experiment has included such questions as the 

 labor in digesting different foods. For example, meat and cheese 

 prepared in different ways have been studied; while an extended 

 series of experiments is to be undertaken to compare different vege- 

 table oils and animal fats and fat constituents with reference to their 

 relative value as sources of energy in the body, and to supplement 

 data regarding the relative value of culinary and table fats of differ- 

 ent kinds. 



Of late a new line of experiments has been undertaken with the res- 

 piration calorimeter, which marks a departure in studies of this kind 

 and indicates a broader application of the apparatus. These new 

 studies relate to problems connected with the ripening of fruit, 

 and are being carried on in cooperation with the Bureau of Chem- 

 istry. They have shown that the apparatus is suited to studies of the 

 changes going on during ripening, and that as a living body the func- 

 tions of the plant as well as of animals may be observed. 



A number of bunches of green bananas were placed in the respira- 

 tion chamber and kept under observation until the ripening process 

 was completed to the usual commercial stage, which requires three or 

 four days. During this time the oxygen consumption, the carbon- 

 dioxid excretion, and the heat elimination were determined in a 

 manner not previously possible, throwing interesting light on the 

 chemical processes of ripening. 



These experiments have been repeated sufficiently to check the re- 

 sults and suggest the nature of the changes. Important data have 

 already been obtained regarding the respiratory quotient, the carbon 

 dioxid thermal equivalent, and the amount of energy liberated by 

 the bananas during the ripening process. The indications are that 



