30 UNIV. OF N. H. AGR. EXPERIMENT STATION [Bulletin 240 



The total energy metabolized (measured by respiration experiments) 

 per 24 hours on the feed level shown in Table IV, all other conditions 

 being constant, was: 



Cj filovias 



1st day full feed 14,530 



2nd " " " 14,780 



1st half feed 



2nd " " " 11,800 



3rd " " " 11,350 



1st day fast following full feed 



2nd " " " " " 9,750 



3rd " " " " " 9,630 



It is not our purpose to discuss the physiological relations of these 

 values, but to illustrate the nature of the data obtained and particularly 

 to point out the relative constancy of metabolism measurements when 

 conditions under which they are carried out are not varied. 



Dependability of Metabolism Measurements 



The degree of usefulness of metabolism measurements obtained by 

 means of respiration experiments is determined by two tests: In the first 

 place, when the conditions of different experiments are identical, the re- 

 sults must be identical. This test shows merely the comparative value of 

 such data. An indication of this test is given in text table above. Second- 

 ly, it is equally necessary that the results of such an experiment be capable 

 of interpretation in terms of absolute values. This test is carried out by a 

 so-called gas check in which definitely measured amounts of carbon dioxide 

 are introduced into the ventilating system and recovered by the usual ex- 

 perimental procedure. ^ Such tests are made several times each season in 

 order to insure that the apparatus is functioning with a degree of accuracy 

 which does not permit of a deviation of more than one per cent from 100. 



CONCLUSION 



It has been the purpose in this report primarily to point out the progress 

 which has been made in design of equipment and in the corresponding 

 technique, whereby it has become possible to make the measurements of 

 animal metabohsm a matter of normal daily procedure rather than an 

 occasional event. The gratifying feature of this progress is that it has 

 been accomplished by simplification of equipment and method rather than 

 by augmenting the former complexities that have made the study of ani- 

 mal metabohsm all but impossible to investigators in general. There has 

 always been a reluctance among investigators not thoroughly famihar 

 with the principles and practice of calorimetric methods to accord more 

 than a mild physiological interest to the results of this kind. Apparently 

 there still exists some confusion relative to the extent to which the physical 

 objectives in animal feeding may be expressed by physiological manifesta- 

 tions. It has been maintained that the latter have no direct bearing on 

 problems of a purely economic nature. This attitude can only be held by 

 those unfamiliar with the continuous and unfailing response with which 

 animal life registers its energetic activities and the extreme sensitiveness of 

 present-day calorimetric apparatus to measure them. 



1 Pubs. 324 and 377, Carnegie Institution of Washington, and New Hampshire Sta. Bull. 

 No. 16. 



