36 COMPARISONS OF RESPIRATORY EXCHANGE. 



Carbon-dioxide absorbers. The carbon dioxide is absorbed by soda- 

 lime, which is placed in containers of the same type as those employed 

 for the tension-equalizer unit, of which a detailed description is given 

 on page 27. A Williams bottle containing sulphuric acid is placed after 

 the soda-lime container in order to remove the water which is given off 

 in the absorption of carbon dioxide by the soda-lime. 



Retention of add fumes. In this apparatus, instead of the air being 

 passed through water containing sodium bicarbonate, it is carried 

 through dry sodium bicarbonate in a brass container, 10.5 cm. in 

 diameter and 11 cm. in height. This container is connected to the 

 apparatus in a vertical position and is packed with alternate layers of 

 cotton and sodium bicarbonate in such a manner that when placed in 

 the ventilating system the layers are in a horizontal position. The 

 bicarbonate and cotton may without renewal be used for several months 

 of experimenting. 



Three-way valve, mouthpiece, nosepieces, and moistener. The three- 

 way valve used for the passage of air from the respiratory tract of the 

 subject to the circulating air-current is the same as that in the older 

 form of apparatus. A cross-section of the valve is shown in figure 1 1 . 

 In the same figure a cross-section is given of the ventilating pipe, the 

 connection for attaching the mouthpiece, and the newer form of air 

 moistener. 



FIG. 11. Cross-section of the three-way valve, ventilating pipe, and connection for 

 mouthpiece and moistener. 



The three-way valve, a, is connected to the main air pipe, c, by means of a tee, b. The mouth- 

 piece, g, is fastened to the metal tube, /, which is connected to the three-way valve, a, by means 

 of the collar, h; d, opening to outside air; e, opening between mouthpiece and three-way valve; 

 m, metal gauze of moistening apparatus. 



An ordinary three-way plug cock, a, is used for the three-way valve. 

 This is ground very carefully and sufficient metal taken from it so that 

 it may be soldered directly to the tee, b, on the ventilating pipe, c. 

 The manipulation and use of the valve are the same as with the tension- 

 equalizer unit (see page 33). 



The mouthpiece is attached by means of a cylindrical piece of brass 

 tubing, /, which is 3 cm. in length and 20 mm. in diameter. This is 

 connected to the three-way valve by a collar, h, which screws to the 

 threaded part of the three-way valve. A rubber washer makes a tight 

 closure. The mouthpiece, which is shown as g in figure 1 1 , is the same 

 as that used with the other types of respiration apparatus. A detailed 

 description is given in connection with the Zuntz-Geppert apparatus. 



