How To Study Living Animals


Directions.

Boil an egg at least ten minutes in water deep enough to cover it. Note which side is uppermost and mark this part of the shell for reference herunterladen. Remove the egg and pick away the shell from about half the egg, leaving the shell on that portion which was underneath when placed in water. With a sharp knife remove this half of the egg herunterladen. Note the thickness of the shell. Test its composition (use hydrochloric acid). Find the membrane lining the shell and note that at one end it separates into two parts to inclose an air space microsoft office kostenlos downloaden vollversion deutsch chip.

1. What is this for? How does it change after an egg has been incubated for a week or more?

Break an uncooked egg in a saucer. Note the germ spot. Note also the difference in the consistency of the “white” (albumen) and yellow portion (“yolk”).

2. Why does the latter retain its shape?

3. Why do the white and yolk not mix unless shaken or beaten together?

4. Look for the chalaza.

5. What do you think is the use of this structure?

Weigh a fresh egg, place it in a dry atmosphere for a week, and weigh it again. Record result. Why may eggs be kept a long time perfectly fresh if coated with paraffin or if put in “water glass”?

Suggested drawings.

a. The egg as it appears in the saucer.

b. The egg after part of the shell has been removed.