connect the two by a bent glass tube one end of which passes 

 through the cork into the air space above the yeast, the other end 

 of which dips below the surface of the baryta water. What 

 changes take place in the baryta water? This is a test for carbon 

 dioxide, (d) Chemical reaction of fluid yeast. Determine by the 

 use of litmus paper whether fluid yeast is acid or akaline in its 

 nature. What do you suppose the cause of this to be? 



Prepare a written statement giving as far as possible an explana- 

 tion of all the facts yon have observed in these experiments. 



IX. BACTERIA SP. 



(Schizophytes). 



A. BACTERIA OF HAY INFUSION. 



Fill three test-tubes J /2 full of a fresh infusion of hay: (i) close 

 one tube with cotton wool carefully and boil a few minutes; (2) do 

 the same with a second tube and then boil it again after 24 hours 

 and repeat the boiling for several days if convenient; (3) leave a 

 third tube open and do not boil it ; set all three in a warm place 

 where they can be observed from time to time. Note the changes 

 which take place in each of the tubes. Does the infusion in any of 

 the tubes become turbid and in which one is this most marked? De- 

 termine by microscopic examination what the cause of the turbidity 

 is. How do you account for the differences between the tubes ? Keep 

 the tubes under examination for several days or weeks and observe 

 in what tubes a scum forms on the top of the liquid. Does the for- 

 mation of this scum have any influence on the turbidity of the fluid? 

 Study the scum under the microscope and determine what it consists 

 of and whether it differs in the different tubes. What ultimately 

 becomes of the scum ? What changes if any are there in the odor 

 of the fluid during the period of observation and how do you 

 account for them? Are different kinds of bacteria found in the 

 tubes? If so make sketches to show them. Do the bacteria in 

 the same tube differ in form from day to day? If so sketch 

 them in the order in which they appear. After one week 

 what is the condition of the fluid and the bacteria found in each of 

 the tubes? Write up an account of the phenomena yon Jiave observ- 

 ed and give your explanation of them. 



B. BACTERIA OF THE AIR. 



Clean a smooth potato with a stiff brush and water, removing with 

 a knife all injured portions as well as the "eyes'". Sterilize the 



26 



