34 EGGS OF BIRDS. 



Though birds are not the only animals which are 

 produced from eggs, and though the eggs of some 

 species of reptiles resemble those of some birds both 

 in size and in colour, yet the egg of a bird is very 

 easily distinguished from that of any other animal. 

 The shell is harder, containing more salts of lime and 

 less gelatinous matter than that of the eggs of rep- 

 tiles, and it is more granular in its surface ; it is 

 also more brittle, though from its shape it is strong 

 in proportion to the quantity of matter in it. Far- 

 ther, the egg of a bird cannot be dinted without a 

 fracture of the shell, while that of almost every 

 other oviparous animal may. The contents of the 

 bird's egg are also chemically different from those 

 of that of the reptile ; indicating even in the rudi- 

 mental state a higher degree of organisation, and 

 along with it, as is always the case, greater energy 

 and activit}' in the powers of life. The egg of the 

 bird is much more albuminous, so that it " boils 

 hard," while that of the reptile consists more of gela- 

 tine. The flesh of the animals have much the same 

 difference of quality. The muscular parts of birds 

 are more dry and rigid than those of even the mam- 

 malia ; and some of them are so hard and tough, as 

 not to be eatable. The tendons and even the mem- 

 branes have the same proportional firmness of struc- 

 ture ; so that the flesh of an eagle is much firmer 

 than the flesh of a lion. Even the bones of birds 

 partake of that firmness which is traceable in the 

 egg. All those which are elongated and cylindrical 

 are hollow ; but there is no marrow in the tubes, 

 and no part of them is cellular with merely a crust 

 of solid bone on the outside, as is the case in many 

 of the bones of the mammalia. They are all remark- 

 ably firm in their texturcj and the shape of the bone 



