SPIROMETER UNIT. 



37 



The nosepieces are of the same form as those described on page 23 

 (fig. 4), and are attached to the three-way valve by means of an 

 arrangement similar to that used for the mouthpiece. It has two brass 

 tubes (d, d, fig. 12), to which the nosepieces are fastened by means 

 of rubber tubing. 



A special device for moistening the inspired air is also shown in figure 

 12. It is commonly assumed that the expired air is saturated with 

 moisture at 37 C., so that when the air breathed into the apparatus 

 by the subject strikes a tube which is colder than 37 C., a deposit 

 or condensation takes place. The moistener in the spirometer unit is 

 constructed to take advantage of this fact. A piece of copper gauze 

 (m in fig. 11 and a in fig. 12) is rolled into a cylinder and inserted in 

 the tube connecting the nosepieces with the three-way valve. This is 

 done in such a manner that the air entering the nose or mouth passes 

 on both sides of the copper gauze. To facilitate the removal of this 



FIG. 12. Details of moistener and connection for nosepieces. 



The air-moistener, a, is inside of a brass tube, to the end of which are connected the tubes d and d 

 for holding the nosepieces. At the left is shown a lateral cross-section. The metal ridge, b, 

 holds the moistener a. Rubber bands for holding the linen on the moistener are shown at c. 



moistener, the edges of the gauze fit into a small strip of metal, 6, 

 soldered to the inside of the tube. Fine cambric is wrapped about 

 the gauze and kept in place longitudinally by a rubber band, c, or by 

 sewing it on. In actual use this cambric is saturated with water, so 

 that the dry air, before entering the nose or mouth, becomes partially 

 saturated as it passes over the moistening device. As some moisture 

 from the expired air is unquestionably deposited, the original amount 

 of water is but slowly evaporated. When once thoroughly drenched, 

 this moistener gives satisfactory service for several experimental periods 

 of 15 minutes and can be readily removed and re-moistened or 

 sterilized whenever necessary. 



Spirometer. The essential modification in this type of respiration 

 apparatus is the insertion of a spirometer in the ventilating air-current, 

 consisting of a cylinder suspended free in a bath of water or oil and 

 counterpoised. Air enters and leaves the bell through tubes connected 

 with the apparatus, the bell rising and falling as the pressure increases 

 or decreases. Devices are attached to record the movements of the 

 bell, which show the quantitative changes in the volume of the respira- 



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