ANIMAL LIFE. 359 



ammonia ; the peculiar pungent smell of which is 

 well known in the solution usually called harts- 

 horn, and which is always more or less perceptible 

 when any animal matter is burnt. That smell is 

 indeed the best test of the presence of animal 

 matter in a state of decomposition. No inorganic 

 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 mecha- 

 nics and chemistry which inorganic matter always 

 obeys, but has a chemistry 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 sup- 

 pose, make every body take an interest in the 

 thousand of living creatures with which all around 

 us is peopled. Take, for example, the egg of a 

 bird. That may be found when not bigger than 

 a grain of mustard seed ; when the whole substance 

 of it is yolk, and the white which contains the 

 embryo, or at least some portion of the embryo of 

 the future bird, is a pellicle of so very pure a tex- 

 ture that it is hardly discoverable. Well, it is 

 brought to a certain stage of maturity by the ac- 

 tion of the parent bird, just as a seed is ripened by 



