Aves. 121 



1. Crack the shell, and pick it away; put a piece of.it in 

 strong vinegar, or other acid. Of what is the shell made? 



2. Note the thin membrane lining the shell. 



3. Does the egg completely fill the shell? Where is the air 

 space? Does the lining membrane, in this region, adhere to the 

 shell or to the " white " ? How can a fresh egg be distinguished, 

 without breaking? Does a fresh egg, in water, lie in the same 

 position as when on a table ? What is the use of this air space ? 



4. How is the yolk situated in the white? How in reference* 

 to the position during boiling? Compare a number of eggs, to 

 see if there is any regularity about this. 



5. Note the round spot on the yolk, where it comes nearest 

 to the surface. This is the germ spot, in which the chick begins 

 to form. 



6. With a sharp knife, split the egg lengthwise. Is the white 

 alike throughout ? Is the yolk alike throughout ? Has the yolk 

 a coat? Cut and tear these parts to make out their structure, if 

 they have any definite structure. 



7. Boil an egg hard, as before ; mark a line lengthwise around 

 the egg, passing through the point that was uppermost while boil- 

 ing ; carefully break away the shell on one side, and with a clean 

 cut remove this half of the white and yolk ; place the other half 

 in the position it had while cooking ; make a drawing of this 

 section, using different colors to show the shell, shell membrane, 

 air space, white, yolk, germ spot, etc. 



8. Prop an egg on end, and boil in this position. Is the yolk in 

 a different position in consequence? The white of the egg has 

 interlacing fibers and partitions which keep the mass together ; 

 the white cannot be mixed with water till these membranes are 

 cut or broken ; hence an egg, to be eaten raw, should be whipped 

 to break these membranes. The white is not a part of the true 

 egg. In dissecting a bird, the eggs, of various sizes, according to 

 their stages of development, may be found in the ovary. At this 

 time the egg consists of the yolk, with a thin coat ; the white is 

 deposited around this later, during its descent through the oviduct ; 



