RESPIRATION 



261 



For very accurate work a tapless modification of the Topler 

 pump, is best employed (Fig. 134). The general arrangement of 

 the parts is shown in the figure, which is drawn to scale one- 

 tenth of the actual size. The pump (P), together with the drying 

 apparatus (D) and condenser (E), possesses neither taps, nor mercury, 

 nor rubber joints, the various parts being glass and sealed together 

 with a blowpipe. The blood is introduced into the froth-chamber, 

 which is made up of a cylindrical bulb (C) and two double-walled 

 condenser bulbs (^4), the lower of 

 which terminates in a barometer 

 tube 85 centimetres long dipping 

 below mercury. This part of the 

 apparatus is sealed on to the con- 

 denser at X. The apparatus is 

 evacuated in the usual way, and 

 the height of the mercury in the 

 vessel B adjusted so that the 

 barometric column just reaches the 

 entrance of the lower froth-bubble 

 (A). In order to prevent the 



3 Nitrogen 



Zarbon 

 Dioxide 



FIG. 133. 



FIG. 134. MODIFICATION OF THE 

 TOPLER TAPLESS PUMP FOE ACCURATE 

 BLOOD-GAS ANALYSIS. (Buckmaster 

 and Gardner.) 



occlusion of air in the mercury, or between the mercury and the glass, 

 after a high vacuum has been produced, the tube AB, and also P, 

 is heated with a Bunsen burner almost to the boiling-point of mercury. 

 The evacuation is then completed. It is now advisable to allow the 

 pump to stand for a day or two, with occasional pumping before use. 

 A very high vacuum can in this way be obtained. The condenser 

 must be large, and as efficient as possible. The drying vessel, filled 

 with pure sulphuric acid, is provided with a tube, the end of which 

 can be easily broken, so that it is easy to refill with sulphuric acid. 



