414 



OF RESPIRATION. 



Wales (as by the last Census) at 20,000,000, the average annual mortality 

 must be 440,000, of which only 220,000 is inevitable, an equal amount being 

 prevcntible. 



Pettenkofer's Respiration Apparatus. 



The construction of Pettenkofer's apparatus, with which so many important inves- 

 tigations have been made, may here be briefly given. A full description illustrated 

 by three plates is given in the Pliysiologische C/iemie of v. Gorup-Besanez. It con- 

 sists essentially of a sheet-iron chamber (A), containing table, chair, and bed, from 

 which the air is slowly exhausted by two pumps (G), worked by a small steam engine. 

 Fresh supplies of air are admitted through ventilators. The greater part of the air 

 is drawn through R, and is conducted into a large receptacle (B) filled with wet 



FIG. 164. 



pumice-stone in order to saturate it with aqueous vapor, and then enters tbe gasom- 

 eter, where its volume is measured. From this it is drawn by the suction of the 

 pumps, and having passed through them escapes into the air. For the analysis of the 

 air in the immediate vicinity of the chamber a tube (/) conducts a certain quantity, 

 which by means of a mercurial exhausting and pressure pump (F) is drawn through 

 the bulb apparatus containing sulphuric acid (?#), it is then made to pass through an 

 inspiratory mercurial valve (v) into F, then through a similarly constructed expira- 

 tory valve (i/) into the u-shaped tube (u), in which it is saturated with watery vapor 

 bv means of moistened pumice-stone. It is then propelled through the tube (k) filled 

 with baryta water, by which the amount of carbonic acid gas present is determined. 

 It then passes through the small meter (D), where its volume is determined, and is 

 finally discharged into the air through the small tube (rl). For the analysis of the 

 air, contaminated with the cutaneous and pulmonary excretion of the subject of the 

 experiment, a small tube (c) is attached to the main discharge tube (K) ; the air thus 

 obtained is conducted through a series of apparatus which is the precise duplicate of 

 that just described, enabling an exact comparison to be instituted. The accuracy of 

 the whole method of investigation was ascertained by control experiments with wax 

 candles, the products of the combustion of which were compared with the amount 

 that direct analysis showed ought to have been obtained. The average error for the 

 carbonic acid did not exceed 0.3 per cent., and for the water 1.5 per cent, for 24 hours. 



