18 



UNIV. OF N. H. AGR. EXPERIMENT STATION 



[Bulletin 240 



forcing the air througii these absorbing fluids is such as to secure speed as 

 well as thoroughness of absorption. The third apparatus (Plate 4, left) 

 is designed' primarily to determine the methane (or marsh gas) in the air 

 sample. Its principle feature in addition to the burette and absorption 

 tiuid for CO 2 is a small, electrically heated, combustion pipette in which 

 the methane of the air sample is broken down by high temperature, thus 

 liberating the CO 2 it contains, the latter being then absorbed in the usual 



Plate 3 — General view of gas analysis room 



way. All three of these apparatus have been thoroughly described by 

 Carpenter. 1 



Duration and Technique of Respiration Experiment 



The duration of a respiration experiment with the large chamber for 

 cattle depends mainly on the purpose in view. In so far as the mechanical 

 utility of the apparatus is concerned, an experiment may be carried out 

 satisfactorily for any desirable period of time from one and a half hours up 

 to a week. Since a daily, or 24-hour, period forms the logical time unit for 

 expressing food requirements and metabolic activities, it follows that all 

 respiration experiments of less than 24 hours' duration must finally be 

 standardized with reference to their relationship to a whole day. At 

 present all our respiration experiments with cattle are carried out on the 

 24-hour basis and are continued for two or three consecutive days in order 

 to check the results. 



An example of the data obtained in eight different experiments with 

 each of two cows is shown in Table II. All conditions were identical 

 during the full feed days. Thereafter the only difference occurred in 

 food supply. 



^ Loc. cit. 



k. 



