1'2 ANIMAL KINGDOM. 



some of its actings as will be shown hereafter ; but yet only a 

 mere internal impulse, and incapable of improvement. The 

 bird shows it in building its nest ; the bee in constructing its cells ; 

 but both the nest and comb are made as skillfully at the first as 

 in any subsequent trial. 



There seems no occasion to mistake by referring to mineralogy 

 or botany what properly belongs to the Animal Kingdom ; and 

 yet in such animals as the oyster we discern but little of the sen- 

 sibility and capacity for voluntary motion which are usually ad- 

 duced as characteristics of the animal tribes. 



Chemistry has ascertained that the substances found both in ani- 

 mals and vegetables are chiefly formed of four elements, viz., car- 

 bon, hydrogen, oxygen and nitrogen. These have, therefore, 

 been called organic elements. The opposite and distinctive 

 natures of plants and animals may be seen in the functions 

 which they perform dependently one on another. In animal 

 respiration, the oxygen of the atmosphere is combined with the 

 blood, forming carbonic acid gas, which is thrown off from the 

 entire surface of the body in some animals ; from the gills of 

 those that live in water, and the lungs of those that live in air. 

 Animals thus consume oxygen to them it is pabulum vitae 

 the food of life. Plants, on the contrary, consume carbonic acid 

 and give off oxygen. They thus become able to furnish animals 

 with carbon. Animals, in their turn furnish food to plants. The 

 excretions which they throw off, yield ammonia (consisting of 

 hydrogen and nitrogen,) from which substance vegetables princi- 

 pally derive their nitrogen. The animal derives the constitu- 

 ents of its body from the vegetable kingdom ; the plant obtains 

 its elements from the mineral kingdom. The tissues of the plant 

 change mineral into organic substances; those of the animal 

 change organic substances into mineral. 



A further contrast between plants and animals is presented in 

 the effects produced upon them, respectively, by light and heat. 

 Both of these are indispensable to the proper growth of plants. 

 The productions found in their tissues are but the expression of 

 the light and heat they have, as it were, appropriated. Many of 

 the substances in this way formed, are taken as food into the 

 systems of animals ; but in them are again set free in the form 

 of "vital animal forces." 



Differences of structure also constitute an important ground of 

 distinction between the animal and vegetable kingdoms ; yet, 

 sometimes, as in the sponge, it is only by considering to which 

 there is the greatest general resemblance, it can be decided 



