THE EESPIRATION CALORIMETER. 1041 



animal, and underneath it is i)laced a galvanized iron box, tightly 

 pressed against the lower side of the platform, to receive the droppings 

 of the animal. This small chaml)er, therefore, has only such air con- 

 nection with the remainder of the chamber as is unavoidable through 

 tli(^ o]:)enings around the two ducts, but is in thermal communication 

 with it through its copper walls. The operation of opening the air- 

 tight door, removing the excreta and replacing the receptacles occupies 

 not more than a minute or two, and it is assumed that any error 

 thus introduced is insignificant. 



At the other end of the platform is the feed box. This is provided 

 with an air-tight cover, which can be opened or closed by means of a 

 lever operated from outside, and is also provided with an air-tight 

 door. B}' lowering the cover the feed box can be entirely shut off 

 from the chamber. The air-tight door can then be opened for the 

 introduction of feed or the removal of residues, the door closed and 

 the lid again lifted. The arrangement constitutes, in brief, an air lock 

 and is substantially like tliat emplo3'ed in the respiration apparatus of 

 the Moeckern Experiment Station. The water supply is introduced 

 into a small drinking basin at the side of the feed box by means of a 

 pipe carried through the calorimeter wall, the water being weighed in 

 and any excess removed by drawing the water in the pipe down to a 

 tixed level. 



The large door at the rear of the apparatus through which the ani- 

 mal enters and the two small doors giving access respectively to the 

 feed box and excreta ha\e hea\'y oak frames and are made tight ))y 

 means of gaskets composed of rul)l)er tubing, the doors being kept in 

 place by means of pressure catches such as are frequently used on large 

 refrigerators. 



THE RESPIRATION APPARATUS. 



Through the chamber above described a current of outdoor air is 

 aspirated b}^ means of a special pump (PL VI), the air tirst passing 

 over the expansion coils of an ice machine where most of its moisture 

 is deposited as frost. At the point of entry to the chamber samples 

 are taken alternatel}' by one or the other of two large aspirators of 

 constant flow at the rate of 200 liters in 12 hours. In these samples 

 moisture and carbon dioxid are determined by passing them through 

 U tubes containing sulphuric acid and soda-lime. 



The air leaving the respiration chamber passes tirst through four 

 large copper cans, standing in wells in a brine bath which is cooled to 

 about —20° C. by means of the ice machine. In these cans the larger 

 share of the moisture of the outcoming air condenses as frost and is 

 subsequently weighed. 



From the copper cans the air passes to the meter pump, which 

 serves both to maintain the air current and to measure and sample it. 



