98 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



Although thoroughly seasoned maple was used for the floor, in a very 

 short time there was sufficient shrinkage to cause extensive diffusion of 

 air through the slight openings. It thus became necessary to include 

 the air in the space under the floor in the total air volume of the 

 chamber. A series of 1-inch holes were bored along the north and 

 south edges of the floor near the walls, to facilitate free passage of air. 



In the east end of the chamber are two large sheets of plate glass, 

 5 feet 10 inches by 39 inches (b^ and 6^ fig. 6), set into rigid frames which 

 terminate in the sheet metal interior wall. Both sheets of glass are well 

 imbedded in a large amount of physicist's wax, which is then covered 

 with shellac. These windows provide full illumination for the cham- 

 ber, as there is but a 2-foot passage between them and the large 

 double window on the outside wall of the calorimeter laboratory. 

 Consequently it has never been necessary to use artificial illumination. 



The roof of the chamber is suspended by three f-inch iron rods 

 (c\ c^, c^ fig. 7) attached to the structural steel beams in the ceiling of 

 the calorimeter room laboratory. This construction is so rigid that a 

 dozen men can walk at any place on the roof of the chamber without 

 causing a perceptible sag. 



The entrance to the chamber is in the northeast corner of the roof. 

 A stout step-ladder, d, one end of which is attached to the wall per- 

 manently, leads down into the chamber. When desired, this ladder 

 can be hooked up out of the way (see e) , a counterpoise rope assisting 

 in its elevation. The corners of the trap door, /, are made of strong 

 sheet copper, reenf orced with a wooden framework . This door is likewise 

 counterpoised by a window-weight and cord running over two pulleys. 

 When the door is lowered, the edge (which is 3i inches deep) fits into 

 a trough, g, surrounding the opening into the chamber. This trough 

 is approximately one-half to two-thirds filled with water, thus sui>- 

 plying a complete seal and perfect freedom in opening and closing. 



In the east end of the respiration chamber is a brine coil, h, connected 

 with the refrigerating brine service of the Harvard Medical School 

 power-house. By opening the valves an unlimited amount of cold 

 brine may be passed through this coil, and the heat generated by the 

 subjects inside the chamber brought away rapidly. To hasten or 

 facihtate this withdrawal of heat the electric fan, which is always placed 

 inside the chamber to insure uniform mixture of air, may be so turned 

 as to deflect the air against the brine pipes. The temperature of the 

 room can be easily controlled by this method. 



The special features to be emphasized in connection with this respi- 

 ration chamber are: (1) it is absolutely air-tight; (2) it provides an air- 

 tight and easily opened and closed entrance by means of a trap-door 

 and water-seal; (3) the glass windows at one end provide complete 

 illumination; (4) provision for cooling is made with the brine coil. 



