STUDIKS ON FERMENTATION. 49 



continue to boil at the ordinary pressure. "We must then leave 

 the flask to cool. It will gradually become filled with air that 

 has been heated to a high. temperature, more than sufficient to 

 burn up all the organic particles of dust which that air could 

 have contained. When the flask is cold we must close the tap 

 and detach it, and proceed to prepare other similar flasks. It 

 will be advisable to close the tap when the temperature of the 

 flask is still a few degrees above that of the surrounding atmo- 

 sphere : this precaution will cause the air in the cooled flask to 

 have a lower pressure than that of the external atmosphere. 



During the interval which must elapse between the prepara- 

 tion and the use of a flask, it is a good thing to keep the free 

 branch of the tap inclined towards the ground, to secure the 

 inside of its tube from the deposit of external particles of dust. 

 Whether this precaution be adopted or not, we must take care 

 to heat this branch in the flame of a spirit lamp just before we 

 bring our flask into requisition. 



If we have to study blood, we must take it from a living 

 animal — a dog, for example. We must expose a vein or an 

 artery of the animal, and make an incision into which the end 

 of the free tap-branch, which has previously been heated and 

 allowed to cool, must be introduced and fixed by a ligature in 

 the vein or artery. On opening the tap, the blood will 

 rush into the flask ; it must then be closed, and the flask placed 

 in an oven at a certain temperature. We have successfully 

 accomplished these manipulations, thanks to the kind help of 

 our illustrious colleague and friend, M. Claude Bernard. 



The operation is nearly the same in the case of urine. The 

 end of the free branch of the tap is introduced into the passage 

 of the urethra ; the tap is turned at the moment when the 

 urine is emitted, which is then allowed to pass into the flask, 

 until it is a third or half filled. 



The following were the results of our experiments : — Blood 

 underwent no putrefactive change even at the highest tempera- 

 tures of the atmosphere, but retained the odour of fresh blood, 

 or acquired the smoll of lye. Contrary to what we might have 



