28 INTRODUCTION. 



centres the impressions received, and to the muscles the in- 

 fluence of the same nervous centres. 



The animal fluids or humours are numerous and in abun- 

 dance. In most animals there is a liquid in circulation in the 

 vessels; it is the blood, which is the principal and most im- 

 portant part of the nutritive liquids; other liquids are absorbed 

 from the surfaces or the mass of the body itself, and others, 

 finally, are secreted or separated from the blood. This latter 

 essentially consists in a very abundant serous vehicle, in which 

 are immersed microscopic bodies similar to those observed in 

 the solids. The composition of the blood is altogether analo- 

 gous to that of the solid parts, and a simple change of state, or 

 some small change in the proportions of the componing ele- 

 ments, are sufficient to produce the conversion of the liquids 

 into the solids. 



The ultimate anatomical elements of the humours and of 

 the organs of animals, appear then to be simply an amorphous 

 substance, liquid in the blood in which it constitutes the serum 

 or the albumen, and concrete in the organs in which it con- 

 stitutes the cellular tissue, and a substance under a globular 

 form, or globules freely floating in the blood, and stationary in 

 the organs where they form the muscular fibre and the nervous 

 substance. The chemical composition of the animal body is 

 more complicated than that of vegetables, and consist in more 

 volatile elements. This is the reason why nitrogen enters into 

 their composition as a very essential part, and is mixed with 

 the other general elements of the organization. Lime is the 

 earthy element most generally found in it. 



13. The general organic phenomena, such as nutrition and 

 generation, are met with in animals, but modified by the phe- 

 nomena which are peculiar to them. Nutrition, instead of be- 

 ing the result of external absorption alone, is induced at the 

 same time, and principally from an internal absorption which 

 occurs in the intestinal cavities. The nutritive fluid taken up 

 in the intestines is submitted to the action of the atmosphere; 

 the result of this respiration, is a production of water and car- 

 bonic acid, which result is precisely the contrary of what hap- 

 pens in vegetables. Besides this, the nutritive liquid needs 



