I 



NUTRITIOK INVESTIGATIONS. 31- 



insures accuracy as well as economy of operation. The new appa- 

 ratus includes a device for the automatic control, as it enters the 

 respiration chamber, of the water current which carries out the heat 

 liberated in the chamber and a device for securing automatically a 

 continuous record of the temperature, as it leaves the chamber, of 

 this water current ; in other words, the measurements of the energy 

 output of the subject are made automatically and continuously with 

 an accuracy which could not be reached hitherto. At the same time 

 the labor of conducting the experiments has been greatly lessened, a 

 matter of much importance in experiments which continue uninter- 

 ruptedly for a number of days at a time. Some of the improve- 

 ments in the respiration calorimeter have been noted in the descrip- 

 tion of it in its present form, which appeared in the Yearbook of 

 the department for 1910. 



During the past year a new line of investigations has been under- 

 taken with the respiration calorimeter, which marks a departure 

 in studies of this kind and indicates a broader application of the 

 experimental method. These newer experiments have to do with 

 problems connected with the ripening of fruit and have shown that 

 the apparatus is applicable to such studies. Several bunches of 

 bananas were placed in the respiration chamber and kept under 

 observation during the active ripening process, which was completed 

 to the usual commercial stage. During this time the oxygen con- 

 sumption, the carbon dioxid excretion, and the heat elimination 

 were determined. The data obtained indicate that physical and 

 chemical factors of great value in the study of this problem, which 

 is of both practical and theoretical importance, can be accurately 

 measured with the respiration calorimeter. 



It has been found very desirable to employ a smaller respiration 

 chamber for such work, since it involves the handling of smaller 

 quantities of fruit and a better control of experimental conditions. 

 Consequently, a respiration calorimeter more suited in size to these 

 particular investigations has been constructed in which the respira- 

 tion chamber is 18 by 18 by 36 inches in size. Recording and con- 

 trolling devices of special construction involving much that is new 

 and original have been used in this apparatus to such an extent that 

 the calorimeter will be very largely automatic in operation and 

 can be operated at the same time and by the eame observers as are 

 employed upon the other calorimeter in experiments with man. 



The work thus far done with ripening fruits was undertaken in 

 cooperation with the Bureau of Chemistry of this department, and it 

 marks the adaptation of the respiration calorimeter to a wider range 

 of investigation along lines in which it has not hitherto been employed 

 and in which investigations have not been numerous owing to a lack of 

 adequate methods. It has demonstti'atecl that the instrument is fully 



