The acquisition of oxygen by the blood in the lung 199 



Therefore it became necessary to reinvestigate the value of the 

 invasion coefficient. 



The bubble proved an excellent medium for this purpose. 



"The method adopted is easily understood by reference to the 

 figure. About 250 c.c. of boiled distilled water contained in the 

 vessel (1) were saturated at 37 C. and at atmospheric pressure with the 

 gas in question which bubbled through (2), and left the vessel through 

 (3). The saturation was in each case continued for at least 24 hours 

 in order to drive out every trace of any other gas which might be 

 present. The oxygen was prepared by electrolysis of water. When 

 the saturation was completed mercury was allowed to flow into the 

 vessel until the water was above the tap (4) which was then closed. 



In the experiments a current of water was conducted past a 

 bubble of gas identical with that in the microtonometer. When the 

 gas pressure in the bubble is equal to the tension of the dissolved 

 gas, the volume of the bubble must remain unaltered, but when a 

 definite difference is set up by raising or lowering the mouth through 

 which the water flows out, diffusion will take place through the 

 surface of the bubble, and the volume will become altered. The 

 mean surface being known and the alteration of the volume during 

 one minute being measured, the invasion may be calculated by the 

 formula given by Bohr 



J/.760 

 p-p = . 



...A uniform current of water was produced by the pressure from 

 the raised mercury vessel (5) which was suspended by the spring (6) 

 adjusted to maintain a nearly constant pressure in spite of the dis- 

 placement of the mercury. The flow was regulated by means of the 

 screw clip (7). When the ordinary clip (8) was opened water flowed 

 on to the microtonometer (9) and set the air bubble (10) in revolving 

 motion. The water flowed off through (11) and was collected and 

 measured in a vessel (12) which could be raised or lowered. The 

 water pressure was indicated by the level in the tube (13), placed on 

 a scale graduated in mm. 



Before each determination the bubble was measured in the 

 graduated tube of the microtonometer. It was then carried down 

 into the funnel, the clip (8) was opened, and the pressure-gauges (13) 

 read off. After exactly one minute the clip was again closed, the air 

 bubble drawn up into the tube and measured anew, and the volume 



