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 



Q, 



'NTRODUCED 



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 



