22 



COMPARISONS OF RESPIRATORY EXCHANGE. 



and the motor for driving it. A pipe connects the rotary blower to a 

 Wolff bottle on the shelf above, containing sulphuric acid and pumice 

 stone. To the exit end of this bottle a second Wolff bottle, also con- 

 taining sulphuric acid and pumice stone, is attached, which is in turn 

 connected with the carbon-dioxide absorber on the top shelf. Next in 

 series is a third water-absorber, its lower portion containing sulphuric 

 acid and the upper portion pumice stone. From this water-absorber 

 a pipe leads to a moistener containing a dilute aqueous solution of 

 sodium bicarbonate. This is connected to the three-way valve by a 

 pipe and rubber tubing. The three-way valve opens to a connection 

 for the nosepieces or other devices through which the subject breathes. 

 The tension equalizer is inserted between the three-way valve and the 



Fig. 2. 



Fig. 3. 



Fig. 2. — Diagrammatic scheme of air-circuit and purifying arrangements of tension-equalizer unit. 

 Fig. 3. — Diagram showing arrangement of Benedict respiration apparatus (tension-equalizer unit. 



This shows nosepieces for breathing, tension equalizer, air-purifying apparatus, oxygen 



cylinder, and testing device for carbon dioxide. 



rotary blower. Piping and rubber tubing lead from the tension equal- 

 izer to the rotary blower. Two petcocks are inserted in the pipe 

 between the moistener and the three-way valve. One is attached to 

 a delicate manometer; the other is for the admission of oxygen. At 

 a point just beyond the third water-absorber is an arrangement for 

 testing the completeness of the absorption of the carbon dioxide. Its 

 exit is connected with the pipe leading from the air-moistener. 



Description and Use of Parts. 



Nosepieces. — In the development of the apparatus special nosepieces 

 were devised, one of which is shown in figure 4. To conduct the air 

 into and out of the nose, a piece of glass tubing, a, is used, which has a 

 length of 6 cm., an internal diameter of 7 mm., and a wall thickness 



