22 TUE COMPOSITION OF LIVING ORGANISMS. 



4. Gently scrape the inside of your cheek with a scalpel. 

 Mount the debris in water or 0.5$ aqueous solution of sodium 

 chloride (normal fluid), examine and sketch the cells. 



5. Tease out a bit of frog's muscle in dilute glycerine. Ex- 

 amine and sketch the elongated cells (fibres). 



D. Living and Lifeless Matter. 



1. Mount in normal fluid a thin bit or section of carti- 

 lage (if possible from the frog's sternum). Observe the cells 

 embedded in the matrix. Place a few drops of dilute iodine 

 solution near one edge of the cover-glass and draw it under 

 by applying a bit of blotting-paper to the opposite edge. Re- 

 move the excess of iodine by drawing through a drop of dis- 

 tilled water. The cells are killed and stained brown ; the matrix 

 hardly stains. 



2. Prepare and mount a thin slice of a potato-tuber from just 

 lelow the skin. Stain with very dilute iodine. The living pro- 

 toplasm is killed and stained brown. The numerous lifeless 

 starch-grains turn blue, or blue-black if the iodine is strong. 



3. Prepare a slide of newt's or frog's blood as in C, 3. 

 Stain with iodine and note the effect. 



4. Make a thin transverse section of a geranium-stem (Pelar- 

 gonium] and mount in water. Search for crystals of oxalate 

 of calcium. When found, observe and sketch. Observe also the 

 thin, lifeless partition-walls composed of cellulose. 



5. Examine a prepared section of bone. The clear basis is 

 composed of lifeless calcium-salts. The minute branching cav- 

 ities (lacunce) were in life occupied by branching living cells 

 (done-cells). 



