74 MODERN SVSTLM. 



ON THE 



DIVISION OF ANIMALS from their ORGANIZATION. 



It is the object of comparative anatomy to point out the dift'crencc 

 which each organ presents when considered in every animal : but this 

 exposition would prove very tedious and intricate, were we obliged at 

 every step to eiuimerate all the animals in which particular organs have 

 a uniform structure. It is certainly much more convenient to indicate 

 them all at once under the name of a class or genus which may com- 

 jirehend the whole : but to enable us to form this arrangement, it is ne- 

 cessary that all the animals which compose a genus or a class, should 

 possess some reseml)lance not only in one, but in all their organs. 



Nature never oversteps the bounds which the necessary conditions 

 of existence prescribe to her: but whenever she is unconfmed by these 

 conditions, she displays all her fertility and variety. Never departing 

 from the small numl)er of combinations that are possible between the 

 essential modifications of important organs, she seems to sport with in- 

 finite caprice in all the accessary parts. In these there appears no ne- 

 cessity for a particular form or disposition. It even frequently happens 

 tliat jiarticidar forms and dis]iositions are created without any apparent 

 view to utility. It seems sufficient that they should be possible ; that 

 is to say, that they do not destroy the harmony of the whole. 



Among these numerous combinations there are necessarily many 

 which have common parts, and there are always a certain number 

 which exhibit very few differences. By the comparison therefore of 

 those which resend^lc each other, we may establish a kind of series 

 which will appear to descend gradually from a primitive type. These 

 considerations are the foundations of the ideas from which certain na- 

 turalists have formed a scale ofhdii^n, the object of which is to exhibit 

 the most perfect, and terminating with the most simple kind of organ- 

 ization — with that which possesses the least numerous and most com- 

 mon jiroperties; so that the mind passes Irom one link of the chain to 

 the other, almost without perceiving any interval, and, as it were, by 

 insensible shades. 



The object of system is to T-cduce a science to its simplest terms ; by 

 reducing the propositions it comprehends to the greatest degree of ge- 

 nerality of which they are susceptible. A good method in comparative 

 anatomy must, therefore, be such as will enable us to assign to each 

 class and to each of its subdivisions, some qualities common to the 

 greater part of the organs. This object is to be attained l)y tAvo dif- 

 ferent means, which may serve to prove or verify one another. The 

 first, and that to which all men will naturally have recourse, is to pro- 

 ceed from the observations of species to uniluig .hem in genera, and 



