96 J. Lindhard. 



various ways. By taking casts on dead bodies he found 144 cc, a 

 number he believes to lie very near the truth. Zuntz (according to 

 information sent to Loewy) found 140 cc. by a similar method. Ac- 

 cording to Loewy, however, this is the anatomical, not the physiolo- 

 gical "dead space". He has endeavoured without success to ascertain 

 the latter directly by breathing into a tube with divisions, the sepa- 

 rate parts of which could be isolated, so that each of the different 

 portions of the expired air could be analysed separately. This 

 method of procedure led, however, to quite improbable results; but 

 the experiments showed quite a definite difference according to the 

 mode of expiration. The "explosive" expiration gave the lowest 

 numbers for the "dead space", "long drawn out" expiration the 

 highest values. Even when Loewy increased the "dead space" con- 

 siderably, but small expirations were required to be able to detect 

 the alveolar CO^ which owing to vortices became mixed with the 

 air from the "dead space". He is of the opinion also that these 

 vortices arise in the trachea and bronchi, and that some physiolo- 

 gical importance is attached to them there. 



As the direct determination was unavailing, Loewy endeavoured 

 to calculate the extent of the "dead space". He knew the amount 

 of an expiration, as also of oxygen used and the height of the baro- 

 meter. By introducing now a supposed value for the "dead space" 

 he could work out the alveolar tension. If he obtained a negative 

 value for this, then the supposed value for the "dead space" was 

 too high, etc. In this way he found that the "dead space" in the 

 person investigated must lie between 100 and 140 — 150 cc. 



Haldane and Priestley^ have endeavoured to determine the 

 alveolar carbonic acid tension by direct analysis of the alveolar air. 

 They thus avoid introducing any uncertainly with the "dead space", 

 which, if their reasoning is correct, they are able to calculate, when 

 they know the composition of the expired air and of the alveolar 

 air, as well as the amount of the expiration. 



Haldane and Priestley's method of procedure is, after a nor-, 

 mal inspiration, to expire quickly and deeply into a rubber-tube 

 provided with a mouth-piece; a sampling receiver is inserted close 

 to the mouth-piece. As soon as the expiration is concluded, the 

 mouth-piece is closed with the tongue, and the air-sample then 

 taken. A corresponding sample is taken, by exspiring as deeply as 

 possible after a normal expiration. These two air-samples, according 

 to Haldane and Priestley, should represent the alveolar air at the 

 termination of the inspiration and at the termination of the expira- 



' The Journal of Physiology. Vol. 32. 



