584 Experiments 



tube and the balloon. The cock r and the rubber tube on its end 

 are also submerged. 



Through the zinc cuff passes a current of water going upwards 

 from below, intended to cool the glass tube. This arrangement, the 

 idea of M. Grehant, has this considerable advantage of stopping 

 or at least of lessening considerably the coagulable froth which 

 rises from the blood under the influence of the vacuum, a froth 

 which may reach the chamber of the pump, mingle with the ex- 

 tracted gas or at least dirty the whole apparatus. 



To make a vacuum in the system described above, I first fit to 

 the rubber fastened on cock r another tube which connects with 

 an ordinary pneumatic machine. In this way I shorten the proceed- 

 ing considerably; the vacuum is next secured perfectly by means 

 of the mercury pump, according to the method described pre- 

 viously. 



However, one would not secure a perfect vacuum, leaving the 

 system at the ordinary temperature of the laboratory; I assured 

 myself of that by very simple experiments, on the details of which 

 I need not dwell here. Now the presence of a small quantity of 

 air at the beginning of the experiment may cause difficulties. To 

 remove it completely, I allow a few cubic centimeters of water to 

 enter balloon D, by opening cock r; then I warm the balloon until 

 the bath begins to bubble; at the same time I cut off the current of 

 cold water which was circulating in the zinc cuff. In this way, 

 the very hot steam which escapes from the balloon drives out all 

 the remaining gas, when the pump is operated, and after the fire 

 is lowered and the current of cold water is allowed to flow, we 

 have reached a vacuum as perfect as is necessary. 



Then after the syringe full of blood is fitted to the rubber tube 

 of cock r, submerging its lower part in the water and opening the 

 cock, the suction due to the vacuum forces the blood into balloon 

 D; then I close the cock and take out the syringe. As a certain 

 quantity of blood remains in the siphon and as it would be difficult 

 to exhaust its gases, I plunge the flexible tube into a little dish 

 full of mercury, and allow the mercury to rise to the point where 

 the tube curves to enter the balloon. 



The blood which has reached the balloon D is subjected there to 

 the temperature of the bath, which I raised successively from 75° 

 to 100°. Now I always boil this bath; I am very well satisfied with 

 the use of this high temperature, and the extraction of the gases 

 has always been much more rapid and complete than when I 

 limited myself, as my predecessors did, to keeping the blood at the 



