INTRODUCTION. Xlll 



Organization pre-supposes life, and the organization of each being, 

 implies 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 

 loots ; 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 mdrition 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, 

 into an internal organ of digestion. Sometimes this internal canal, or 

 digestive cavitv, has the form of a tube with two orifices the one for 



