6 LIVING CELLS {!) 



Exercise I 



(11) By moving your slide about gently while 

 it is in focus, try to get used to the fact that the 

 microscope reverses as well as magnifies every 

 motion. In a little while you should have this 

 under control. Also, in fresh preparations sus- 

 pended in a liquid medium, do not be surprised 

 to find all very small particles engaged in a con- 



tinuous, random motion. This is called Brown- 

 ian movement. It is caused by the fact that 

 all objects suspended in a fluid medium are 

 continuously bombarded by the molecules all 

 about them; and sufficiently small particles 

 are continuously knocked about by this bom- 

 bardment. 



EQUIPMENT 



Throughout the manual these lists and the instructions which often 

 accompany them are included for the use of the instructor. 



Per student 



compound microscope 



Per 8 students 



slides and cover slips 



onion 



potato 



Elodea 



cultures of Spirogyra 



Volvox 



other algae 



iodine and potassium iodide in water (0.01 M each) 



methylene blue solution 



sodium chloride solution (2 M) 



Per laboratory 



charts on the compound microscope 



