THORAX. 



1069 



tube ; the height to which the receiver is 

 raised, indicates the volume of the vital capacity . 



To Prepare the Spirometer for Use : 

 1st. Place the spirometer about three feet 



from the ground, upon a firm, level table. 

 2nd. Turn off the water-tap 4, and open the 



air- tap 1. 



Fig. 704. 



sufficient to bring the water down to the 



edge of the index. 

 5th. Pour a little coloured spirit into the bent 



tube 5, until it stands about 3 inches, as 



at 6. 

 6th. Turn off the air-tap 1, then suspend 



the counterbalance weights, 11,11, from the 



cord over the pullies. 



The spirometer is now ready for an observa- 

 tion. The flexible tube, terminated with a glass 

 mouth-piece, is held by the person about to 

 be examined, and the tap 1 is to be kept 

 open by the operator while the deep expira- 

 tion is being made. 



To discharge the air out of the receiver. 

 It will be seen that if the tap 1 be opened, 

 the receiver will rise out of the reservoir by 

 the power of the counterbalance weights, 

 until it touches the cross-head 9. To return 

 the receiver into its original position, the con- 

 tained air must be discharged ; this can be 

 done by slowly depressing the receiver down 

 into the reservoir, and so pressing the air out 

 by the way it entered, through the air-tube. 

 But, in order to do so more rapidly, a large 

 valve at 14 admits of an instantaneous escape 

 of the air. Therefore, to discharge the air, 

 remove the plug 15 out of the socket 14 with 

 one hand, while the other returns the receiver 

 into its original position. 



Let the person to be examined loose his vest, 

 and any other tight garment for the least 

 pressure from dress affects the mobility 

 stand perfectly erect (fg. 705.), with the head 



Fig. 705. 



Spirometer. 



3rd. Pour into the spout, behind, clear cold 

 water, until it is seen to rise behind the 

 slip of glass 3 (above the air-tube). 



4th. Slide the moveable index 2, opposite 

 on the graduated scale 13, and add more 

 water until it is ex actly on a level with the 

 straight edge of this index ; if too much 

 water be poured jn, draw off, by the tap 4, 



thrown well back ; then slowly and effectually 

 fill his chest with air, or inspire as deeply as 

 possible, and then he must lift the mouth- 

 piece of the spirometer 12 to his lips, still 

 standing in the same erect position, and 

 place the glass mouth-piece between the lips, 

 holding it there sufficiently tight so as not 

 to allow any breath to escape, he then sloivly 

 makes the deepest expiration, displacing all 

 the air he can out of his lungs through the 

 mouth-piece into the spirometer, where it is 

 measured to cubic inches, and confined there 

 by a stop-cock, until examined. This ob- 

 servation should be taken three times. The 

 operator, while the experiment is going on 

 should place his left hand upon the shoulder 

 of the person being examined ; in this way he 

 can determine as to the perfect inflation of 

 the lungs and expulsion of air from them as 

 well as the character of the thoracic expansion. 

 The thumb of the operator should cross the 

 clavicle, while the fingers rest on the upper 



