THE FARMER AT JJOME 301 



NUTRITION. In Physiology, a furfe^fc^iamon to all organ- 

 ized bodies, in which their various component tissues convert nutritive 

 matter into their own substance and add it to the particles which pre- 

 viously entered into their composition. The materials of nutrition are 

 prepared by several previous processes ; by digestion, in which the 

 food is altered in its qualities, and reduced to a homogeneous mass ; by 

 absorption, in which this nutritive part of the aliment is extracted and 

 conveyed into the blood ; by circulation and respiration, in which this 

 nutritive matter is converted into blood. Nutrition is the completion 

 of the functions of assimilation ; the aliment, animalised by the series 

 of processes just enumerated, and rendered similar to the substance of 

 the being which it is to nourish, is applied to the organs, whose waste 

 it is to repair ; and this identification of the nutritive matter to our 

 organs, which take it up, and appropriate it to themselves, constitutes 

 nutrition, in which there is a real conversion of the aliment into our 

 own substance. 



The component particles of an animal body are in a state of con- 

 stant change ; the old ones are detached and removed by the absorb- 

 ents, and their place is supplied by new matter laid down by the 

 arteries. Until the body has attained its full size, the movement of 

 composition predominates over that of decomposition, and all the parts 

 increase ; when the growth is completed, and there is no apparent 

 change of bulk, they are moved and the added portions balance each 

 other ; and, as the body declines, the absorption exceeds the addition 

 of new matter. But, at all times, there is an interior motion of the 

 component parts. Hence the body has been compared by a French 

 physiologist to the vessel of the Argonauts, so often repaired in the course 

 of a long and perilous navigation, that on her return, no part of her 

 former materials remained. 



An animal body probably contains none of the same molecules at 

 two distant periods. The experiments performed by mixing madder 

 with the food of animals, prove most unquestionably this incessant de- 

 composition of animated and living matter. This mixture, in conse- 

 quence of a chemical affinity between the madder and phosphate of 

 lime, dyes all the bones of a red color ; when the madder is left off for a 

 sufficient length of time, the color disappears. It is obvious, that the 

 calcareous phosphate in the osseous system previous to the commence- 

 ment of the experiment, must be gradually removed, and its place 

 supplied by the colored earth ; while this is again absorbed in its 

 turn, after the madder is discontinued, to make room for a new un- 

 colored deposition. If the hardest and most solid parts, apparently 

 the most calculated to resist decay, are undergoing perpetual motion 

 of decomposition and regeneration ; there can be little doubt that this 

 motion must be far more rapid in those, whose power of cohesion is 

 much inferior ; for example, in the fluids. In the nails, hair, and 

 cuticle, a constant growth is so regularly observed, that it is not ne- 



