INTRODUCTION. Xl 
Organization pre-supposes life, and the organization of each being, 
) nplies the life proper to that being. Life, indeed, is never seen, but 
in connection with an organized body; and all the ingenuity of the 
materialist has failed to show, that particles of matter can organize 
themselves, or be organized by any combination known in chemistry 
In fact, vitality exercises upon the elements, which form at each 
instant part of the living body, an action contrary to what the ordi- 
nary chemical affinities can produce, without this master agent; and 
no power in Nature is known, capable of reuniting again, in the same 
manner, the atoms which have been disjoined by death. 
Animal life is distinguished from vegetable life, by the power of 
locomotion and sensation; the first is active—the other passive. 
The nourishment of plants is derived through the medium of their 
roots ; that of animals, through a central organ of digestion, destined 
to receive the food. The organization of this cavity and its appur- 
tenances, varies according to the nature of the aliments, and the alte- 
rations which they undergo, before furnishing fluids proper to be 
absorbed ; while the atmosphere and the earth supply vegetables with 
juices, ready for absorption. Animal bodies, besides, at least those 
classes higher in the scale of existence, possess a circulating system, 
muscles for voluntary movements, and nerves for sensation. Respira- 
tion is another essential function in the animal constitution ; and in 
proportion as the respiratory system is complete, the animal functions 
are more fully exercised. In addition, also, to the chemical elements, 
which enter into the composition of vegetables—oxygen, hydrogen, 
and carbon—a fourth substance, azote, seems almost peculiar to the 
animal constitution. ‘To complete the distinction between animal and 
vegetable life, Hedwig has ingeniously remarked, that in vegetables, 
the sexual organs fall each year, or at each production, while animals 
preserve them through the whole course of their existence. 
As nutrition is the most general function of living bodies, under 
the name of organs of nutrition, are comprehended all the parts of 
the body by which alimentary matters are introduced for its support ; 
or which are employed in preparing the food for that purpose. The 
materials of nutrition penetrate, by various means, into organized 
bodies. They may either be introduced under the form of elastic 
fluids, by the pores, or imperceptible interstices, in all living bodies, 
or they may be conveyed by a particular organization for this purpose, 
ito an internal organ of digestion. Sometimes this internal canal, or 
algestive cavity, has the form of a tube with two orifices the one for 
