Appendix I. On method* 



311 



I have always used Haldane's method, and it is by that method that all the 

 results in the foregoing chapters have been obtained. Indeed the simplicity of 

 the apparatus required and the ease and rapidity with which the determinations 

 can be carried out by it, makes it much the more suitable of the two methods for 

 work outside the laboratory. 



I will therefore proceed to describe the method. A rubber tube six feet in length 

 and | 1 inch in bore, is fitted with a glass mouthpiece round which the lips fit 

 tightly. This mouthpiece must be at once large 

 enough to offer no appreciable resistance to the 

 respiration and small enough to be easily occluded 

 by the tongue. About one inch from the end of 

 the rubber tubing is a hole about 4 or 5 mm. in 

 diameter, just large enough to take an ordinary 

 piece of glass tubing. 



In the laboratory this piece of tubing is put directly on to the burette of a 

 Haldane's gas analysis apparatus. The tap is turned diagonally as shown in Fig. 153, 

 after the whole burette has been filled with mercury up to the point A. The 

 mercury reservoir of the burette is then lowered almost 

 to the bottom of the burette. (The operator must be 

 careful that he has a tap good enough to stand this 

 procedure.) The apparatus is now ready for the deter- 

 mination. The subject of the determination applies 

 his mouth to the mouthpiece, taking care to breathe 

 normally through his nose all the while this is the 

 most difficult part of the experiment then suddenly 

 either at the beginning or at the end of one of the 

 normal respirations he shuts his nose and makes an 

 expiration so forcible through the tube that he expels 

 all the air he possibly can along the tube and at the 

 end closes the tube with his tongue. Either he or an 

 assistant then turns the tap to the vertical position for 

 a moment, the burette fills itself with alveolar air and 

 the stopper is then turned back to the position shown 

 in the figure. The analysis is carried out in the manner 

 described. 



It is best to take one sample at the end of a normal 

 inspiration and one at the end of a normal expiration and average the two. 



In many cases it is not convenient to carry a gas analysis apparatus to the place 

 where one wishes to make a determination of the alveolar air. One then takes the 

 sample into a Haldane's gas sampling tube instead of directly into the gas burette. 



This tube is shown in Fig. 154 attached to the gas burette. 



The taps of the tube are adequately greased, and if it is necessary to carry the 

 tube about it is best to be able to prevent all possibility of the stoppers either coming 

 out or accidentally turning by fixing them in position by means of stout rubber rings 

 (for this and similar purposes I use the rings sold for use on umbrellas). The tube is 

 rendered vacuous in the laboratory and the taps placed so that the vacuum is shut 

 oft' from the air. When it is necessary to take the sample of alveolar air this sampling 



FIG. 153. 



