596 



Experiments 



I can thus diminish the pressure 20 centimeters in 5 minutes, 

 40 centimeters in 10 minutes. I can get a pressure of 25 centimeters 

 easily enough in 20 minutes; but I have had the greatest difficulty 

 in going below this figure, and could not get below 17 centimeters. 



We see in the figure an independent cylinder B. I used it as a 

 vacuum reservoir, if I may use this term, in certain experiments. 

 Finally, the tube, which in the figure communicates with a glass 

 bell-jar C, is the one which I later fitted to the table with pneumatic 

 plates represented in Figure 15. 



Fig. 28 — Dog prepared to be placed in the cylinders of Figure 27 and to 

 serve for the extraction of blood under diminished pressure. 



The extraction of the blood of a dog placed in such an apparatus 

 is a rather difficult enterprise. 



The animal is first securely attached on its back, as shown in 

 Figure 28, to the uprights of a sort of cage of solid wood, curved 

 so as to conform exactly on its convex edge to the concavity of 

 the cylinder, and capable of being fastened to it by holes which fit 

 over the hooks of strong staples screwed to the sides of this cylin- 

 der. The head of the animal is held in a sort of movable muzzle, 

 which allows the neck to be extended according to the require- 



