Cuvlerian System of Zoology. 3 1 3 



Cuvier, however, admits that the application of this definition 

 to certain individuals may be very difficult, where necessary 

 experiments have not been made. In few countries have 

 experiments on the different species of domestic animals been, 

 more extensively made than in England, and it has been ascer- 

 tained that almost any accidental variety of form may be per- 

 petuated, by selecting and breeding in succession, for four or 

 five generations, from the individuals that possess it. Thus, 

 several distinct races of horses, sheep, bulls, and pigs, have 

 been formed within the last sixty years, which will remain 

 permanent, if the breeds be preserved from admixture with 

 other varieties ; but these breeds do not constitute species. 



The functions of organic life, described in the preceding 

 part of this essay, are common to all organised living bodies, 

 whether animal or vegetable : they consist, says Cuvier, of 

 absorption, assimilation, exhalation, growth, and generation. 

 Birth and death are the universal limits of the existence of 

 organised bodies. The essential condition of their structure 

 is a porous or fibrous texture, containing within it {dans ses 

 mailles) liquids or gases in motion. The essential parts of 

 their chemical composition consist of substances which are 

 almost all convertible into liquids or gas, and of combinations 

 which can easily change into each other. Fixed forms, which 

 are perpetuated by generation, distinguish their species, and 

 determine the complication of the secondary functions proper 

 to each, and assign to them the part they are destined to per- 

 form in the assemblage of universal beings. These forms 

 neither produce nor change themselves; life supposes their 

 existence : it cannot be kindled but in organic bodies com- 

 pletely prepared for its reception ; and the most profound 

 meditations, as w^ell as the most delicate observations, terminate 

 in the mystery of the preexistence of germs. 



It has been before stated, that the principal chemical ele- 

 ments of which organised bodies are composed are oxygen^ 

 hydrogen^ and carbon^ and that animal bodies contain an addi- 

 tional element, azote. In animal bodies there are three forms 

 of organic texture {tiss2i), the cellular {la cellulosite), the 

 muscular fibre, and the cerebral or medullary texture. 



The cellular texture is composed of an infinite number of 

 minute laminae, placed without regularity, and forming small 

 cells, which are open to each other. It is a kind of sponge, 

 which has the same form as the whole body, and all the other 

 parts fill it or traverse it. Its property is to contract indefi- 

 nitely, when the causes which kept it extended cease to act. 

 The cellular texture compressed, forms those more or less 

 extended laminae called membranes ; the membranes, when 



