ATMOSPHERIC PRESSURE CHANGES 119 



going to the manometer while more oxygen is run in. Do 

 not Now out the mercury by turning on the oxygen sud- 

 denly. What effect has this increased pressure on the ani- 

 mals f 



2. If a suction pump (or negative air pressure) is avail- 

 able this may now be used. Open the outlet and connect 

 this to the suction pump or negative pressure faucet. Open 

 the clip to the manometer and exhaust the air in the bottle 

 as many centimeters of mercury as the oxygen pressure has 

 been raised. What effect has this on the animals? 



3. Wait a few minutes to note how the animals act and 

 then again open the outlet and equalize the pressure inside 

 and outside of the bottle. Koll up four or five sticks of 

 sodium or potassium hydrate in wire gauze and put them 

 in the bottle in such a position that the animals cannot 

 touch the alkali. What is the purpose of this? Be sure 

 the alkali does not rest directly on the bottom of the bot- 

 tle. Why? Allow the animals to become quiet again and 

 then begin to gradually run N 2 into the bottle, leaving the 

 outlet open as gas is injected. Bring on the anesthesia by 

 very gradual degrees and do not excite the animal if pos- 

 sible. Do you notice any symptoms of somnolence in either 

 animal! Or do you note symptoms of excitement and con- 

 vulsive jumping-like movements? After the animals be- 

 come completely anesthetized begin to admit oxygen. How 

 long does it take to produce complete anesthesia? Be care- 

 ful that the oxygen does not become too low. If th ; s occurs 

 one animal may die. Which one? Is it possible f o you to 

 estimate how much oxygen (i. e., what per cent) you admit 

 by closing the outlet and raising the atmospheric pressure 

 in the bottle a given number of millimeters of mercury? 

 Try to so balance the proportions of N 2 and oxygen in the 

 bottle that you can maintain a regular anesthesia in the 

 animals for ten or fifteen minutes. 



4. Now gradually admit more and more oxygen and note 



