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 albwmen, 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 Jime and 
phosphorus which harden the bones of vertebrated animals, 
the tron 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 nutrt- 
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, 
ait 
