RESPIRA TION. 



97 



experiment at a distance in the classroom, place a small quantity of a solu- 

 tion of eosin r.bove each column of mercury. Insert the other end of the 

 manometer through the preforation in 

 the rubber cork. It must fit very tightly. 

 If there is another perforation plug it 

 with a glass rod. Take a wide-mouthed 

 small glass jar — a small glycerine jelly 

 jar is good — which will go inside the 

 cylinder. Break a few sticks of caustic 

 potash and drop in it. Nearly fill with 

 water and tie a string around the top 

 so that it can be lowered into the upper 

 part of the cylinder without spilling any 

 of the potash solution. Prepare a sup- 

 port for this by inserting a glass rod 

 about lym long into a cork. Have all 

 the parts of the apparatus and the ma- 

 terial ready, and the baryta water in 

 the open vial, so that the apparatus 

 may be set up quickly. Have the cylin- 

 der warm and set the apparatus up in a 

 room where the temperature is about 

 2o° C. (about 68° Fahr.). Place a small 

 quantity of damp paptr (not wet) in the 

 bottom of the cylinder. Place in the 

 soaked peas to fill about 8cm to locm. 

 Upon these place the small vial of baryta 

 water. Drop in the support and press 

 the glass rod down far enough so that 

 the jar of potash solution will enter and 

 pass far enough below the mouth of the 

 cylinder to be out of the way of the 

 rubber cork. 



Insert the rubber cork containing the 

 S manometer of mercury, placing be- 

 tween it and the side of the cylinder a 

 stout needle to allow the escape of air 



Fig. 76. Fig. 77. 



Experiment to demonstrate respiraton. 

 Fig. 76. — At beginning" of experiment ; 



while the cork is pressed in tightly, mercury in each arm equal No oxygen has 



T-. ■ T1 .t t . been consumed in vessel. 



This allows the mercury to remain at Fig . 77 ._ At close of experiment ; mer- 



the same level in both arms of the tube J^y in inner arm has risen. Some oxygen 



has been consumed. 

 Now remove the needle and set the 



apparatus aside where the temperature will remain at about 20° C. , and let 



