PROBLEM [[) 40 



4. NOTE. — The jointed, vertiral pillar Rives attachment to the arm. H.ipj.i.rt- 

 ing the main tube of the instrument. 



What are the advantage.s of having the pilhir jointed? 



5. NOTE. — Extending forward from the pillar below (he arm is fho HtaKc on 

 which is placed the object to be examined. 



Describe the location of the perforation in (he stage. Wliat i.s ius um''.' Wh.ii 

 is the use of the revolving wheel, or diaphragm, pivoted to tlie .stage? 



G. NOTE. — Below the stage is a movable bar (P), carrying the mirrors or 

 reflectors. 



In how many different directions can you move the mirrors? What i.s tho 

 advantage of havi<ig them movable? What kind of surface d(. the mirrors rcs[>ec- 

 tively show? What is the use of the mirrors? 



7. NOTE. — A hollow cylinder containing two lenses fits into the upper 

 end of the tube. It is called the eyepiece or ocular. (G). 



Why is the name eyepiece applied? 



8. NOTE. — Small brass mounts, each containing several lenses, are attached 

 to the tube at its lower end; they are the object lenses or objectives (F, F). 



Why is the name objective given to these lenses? How many objective.s arc 

 there in your microscope? 



9. NOTE. — The low power (a slightly magnifying objective) has a .short and 

 broad mount. The high-power objective has a long and narrow mount. 



What fractional numbers do you find on the mount of the high an<l the low 

 power objectives, respectively? 



10. Note. — The objectives are attached to a revolving device, the nose piece. 

 What are tTie advantages of a revolving nose piece? 



11. Note. — To obtain a clear image of the object under examination, we must 

 be able to vary the distance between the lenses and the object ; that is. to focus 

 the instrument. The microscope is brought into focus by slightly turning either 

 of the large wheels placed at the top of the arm near the tulK*. 



Why are these wheels called the coarse adjustment? (Turn one of them gently !) 

 W^hat movement results? 



12. NOTE. — The milled head of the fine adjustment is found at the top of tho 

 pillar. 



Carefully turn the fine adjustment back and fortli. (Xo more than half a turn 

 in either direction!) Why is this adjustment called "fine"? 



Problem. 19: To deterinine tlie unit of striictnrr in jtlant^i 

 and animals. 



Materials. — Onion skin, scrapinjz;s from mouth, compound 

 microscope, slides, methyl blue. 



Method. — Scrape some cells from the inside linini:: of tiie clicok 

 with a sterilized knife. Mount in water. Stain with methyl Mue. 

 Onion skin may be used and stained with methyl blue or iodine. 



Note. — a cell is a .small living structure made up of living matter (proto}>lasm) 

 containing a portion which in part readily absorbs stain. This structure ia called 

 the nucleus. A cell is usually bounded by a cell wall or ccJl membrane. 

 HUNTER LAB. PROS. — 4 



