LABORATORY STUDIES 103 
test tube, when they will rise to its closed end. Respiration 
in its first (anaerobic) stage will go on and gas will 
be formed, oftentimes driving nearly all the mercury 
out of the tube. Introduce a strong KOH solution 
or a piece of stick KOH and a little water under 
the edge of the test tube and the gas will all be ™%,%° 
absorbed, showing that it is CO. that was produced. re 
(q) Yeast plants ordinarily carry on only this first ment 
stage of respiration (called fermentation in this case). 
To potato water (made by grating up a potato and boiling it in 
a little water and expressing the latter) add about 5 per cent. 
glucose. Place in a flask with a cork and a glass tube bent so as 
to lead the gas produced under water. Break up part of a cake 
of compressed yeast in a little water and add it to the solution in 
the flask and insert the cork and glass tube. In a short time 
gas will begin to escape in bubbles from the end of the tube. 
Collect some in a test tube and test in various ways such as for 
inflammability, absorption by KOH, etc. It will be found to 
be CO.. Note what large amounts are produced. After the 
evolution of gas has ceased the proper chemical tests will show 
the presence of alcohol in the liquid. Distill the latter and 
collect the first part that comes over. Add to it some strong 
KOH solution and some flakes of iodine, and heat. If alcohol is 
present a strong odor of iodoform will be produced and if much 
is present this will show as a yellow precipitate. 
(r) The liberation of heat during respiration can be demon- 
strated by placing a quantity of soaked peas or a number of 
mushrooms just expanding in a flask with an accurate chemical 
thermometer bulb in their midst and placing this flask in a 
mass of cotton in another vessel and covering all with several 
layers of cloth, leaving only the thermometer tube exposed. 
Often the temperature within the flask will rise 3 or 4 degrees 
or more above that of the surrounding air. Of course this 
experiment must be carried on ina room where the temperature 
is fairly constant. If a Dewar bulb or a Thermos bottle is used, 
these being double walled with a vacuum between so that the 
loss of heat is very small, the difference of temperature is 
much more marked. 
(s) Without special thermostats where temperatures can be 
controlled exactly, satisfactory experiments as to the cardinal 
points of temperature cannot be made. However, it will be 
