INTRODUCTION. 15 



or filaments peculiar to them, all that is ever wanted for 

 their manifestation being a little repose. The blood also con- 

 tains another combination, which is found in many animal fluids 

 and solids, called albumen, whose characteristic property is 

 that of coagulating in boiling water. Besides these, the blood 

 contains almost every element which may enter into the com- 

 position of the body of each animal, such as the lime and 

 phosphorus which harden the bones of vertebrated animals, 

 the iron from which it and various other parts receive their 

 colour, the fat or animal oil which is deposited in the cellular 

 substance to supple it, &c. All the fluids and solids of the 

 animal body are composed of chemical elements found in the 

 blood, and it is only by possessing a few elements more or 

 less, that each of them is distinguished; whence it is plain, that 

 their formation entirely depends on the subtraction of the 

 whole or part of one or more elements of the blood, and in 

 some few cases, on the addition of some element from else- 

 where. 



These operations, by which the blood nourishes the fluid or 

 solid matter of all parts of the body, may assume the general 

 name of secretions. This name, however, is often appropriated 

 exclusively to the production of liquids ; while that of nutri- 

 tion is more especially applied to the formation and deposition 

 of the matter necessary to the growth and conservation of the 

 solids. 



The composition of every solid organ, of every fluid is pre- 

 cisely such as fits it for the part it is to play, and it preserves 

 it as long as health remains, because the blood renews it as 

 fast as it becomes changed. The blood itself by this continued 

 contribution is changed every moment, but is restored by di- 

 gestion, which renews its matter by respiration, which delivers 

 it from superfluous carbon and hydrogen, by perspiration and 

 various other excretions, that relieve it from other superabun- 

 dant principles. 



These perpetual changes of chemical composition form a 

 part of the vital vortex, not less essential than the visible 

 movements and those of translation. The object of the latter 

 is, in fact, but to produce the former. 



