650 



Experiments 



which mercury is poured; it is closed by a stopper with two holes, 

 through which two glass tubes pass. One, a, is dipped into the mercury 

 to a depth of 381 mm., half of 762 mm.; it opens into the air and has 

 a cock r. The second tube, b, which reaches merely to the upper part 

 of the tube full of mercury, curves outside into a siphon which is 

 joined by a rubber tube, c, to the central tube which projects from the 

 middle of the little mercury basin C which tops the cock R of the gas 



Fig. 44 — Apparatus to bring blood into contact with the air at a specified 

 decrease in pressure. 



pump; when this cock is turned as the figure shows, and cock r is 

 opened carefully, the outer air is admitted bubble by bubble through 

 the mercury, and when the air which has come in contact with the 

 blood has a pressure equal to a half atmosphere, the outer air ceases to 

 enter through tube a. 



The blood then is agitated by raising and lowering the balloon of 

 the extraction apparatus, and the agitation is made 25 times with air 

 and with mercury; the blood becomes a very bright red. 



