332 THE EGG; 



or shells, and both of these are found to contain 

 lime, a substance of which most plants contain none, 

 and some only a very little. But this lime, which, 

 in itself, is not, strictly speaking, animal matter, is 

 always in the living, or the recent state, cemented 

 together by more or less of animal matter ; and all 

 animal matter contains nitrogen, which is usually 

 regarded as the inactive ingredient of atmospheric 

 air; When the animal substance is burnt, a portion 

 of the nitrogen combines with the hydrogen of water, 

 and forms ammonia ; the peculiar pungent smell of 

 which is well known in the solution usually called 

 hartshorn, and which is always more or less per- 

 ceptible when any animal matter is burnt. That 

 smell is indeed the best test of the presence of ani- 

 mal matter in a state of decomposition. No inor- 

 ganic substance is composed of the same ingredients 

 as animal matter; and though some few vegetable 

 products, such as Indian rubber, and the other juices 

 alluded to, resemble animal matter, they are always 

 accompanied in the same organization with other 

 parts which are wholly and obviously vegetable. 



Thus, the " living principle," which is the name 

 usually given to the fact of organization in a state of 

 action, not only suspends those laws of mechanics 

 and chymistry which inorganic matter always 

 obeys, but has a chymistry and mechanics of its 

 own, by means of which it can dissolve those sub- 

 stances which contain the materials necessary for 

 the growth or the repair of its own structure, works 

 these into the necessary new compounds, and gives 

 them the proper forms and consistencies. 



In any one instance, that, when we think of it, 

 is truly wonderful, and should, one would suppose, 

 make everybody take an interest in the thousands 

 of living creatures with which all around us is peo- 

 pled. Take, for example the egg of a bird. That 

 may be found when not bigger than a grain of mus- 

 tard-seed ; when the whole substance of it is yelk, 



