INTRODUCTION. ^l 



the knowledge of the individual, so that, although the will is truly a 

 means of causing the fibres to act, it is neither general nor unique. 



The fleshy fibre has for its base a particular substance called 

 fihrine^ which is insoluble in boiling water, and which seems natu- 

 rally to assume this filamentous disposition. 



The nutritive Jluid or the blood, such as we find in the vessels 

 of the circulation, is not only mostly resolvable into the general 

 elements of the animal body, carbon, hydrogen, oxygen and azote, 

 but it also contains fibrine and gelatine, almost prepared to contract 

 and to assume the forms of membranes or filaments peculiar to 

 them, all that is ever wanted for their manifestation being a little 

 repose. The blood also contains another combination, which is 

 found in many aninial fluids and solids, called albumen whose cha- 

 racteristic property is that of coagulating in boiling water. Besides 

 these, the blood contains almost every element which may enter into 

 the composition 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 supply 

 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 sub- 

 straction 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 nutrition is more espe- 

 cially applied to the formation and deposition of the matter necess- 

 ary to the growth and conservation of the solids. 



The composition of every solid organ, of every fluid is precisely 

 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 digestion, which renews its matter 

 by respiration, which delivers it from superfluous carbon and hydro- 

 gen, by perspiration and various other excretions, that relieve it 

 from other superabundant principles. 



