GENERAL BIOLOGY 



desired thoroughly dry the glass after rinsing and mount4n Canada 

 Balsam. 



Treat some of the Zoogloea in the same way and observe that the 

 bacteria stain more deeply than the substance in which they are 

 imbedded. 



IV. BACTERIA FROM THE MOUTH. 



Take some scrapings from the teeth, dilute with water, mount 

 and study the various forms under a high power. How many kinds 

 of bacteria can you find? 



V. STUDY OF CULTURES IN HAY INFUSION. 



Study the tubes of hay infusion which were prepared and set 

 aside on a previous day (see (A. i). 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? Determine 

 by microscopic examination what the cause of the turbidity is. 

 How do you account for the differences between the tubes ? Where 

 did these organisms come from and how did they get into 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 formation 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 ob- 

 servation, 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 fronvday 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 you have 

 observed and give your explanation of them. 



VI. STUDY OF CULTURES ON POTATO. (See A. 2.) 



Observe on the potato variously colored spots or "colonies." 

 Are all of these colonies bacteria? Are all the organisms in a 

 colony alike? What is the significance of this fact? What kinds 

 of organisms are most abundant in the air of the room? Can they 

 undergo drying without being killed? Can they grow and multi- 

 ply without food and moisture? 



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