INTRODUCTION. 165 



tative soul, and of the nature of the soul itself, judging from 

 its members or organs, and their functions.. 



This, indeed, cannot be done in all animals : first, because a 

 sufficient number of several of these cannot be commanded; 

 and again, because, from the small size of many, they escape 

 our powers of vision. It must suffice, therefore, that this is 

 done in some kinds which are more familiarly known to us, 

 and that we refer all the rest to these as types or standards. 



We have, therefore, selected those that may tend to render 

 our experiments more undeniable, viz. the larger and more 

 perfect animals, and that are easily within reach. For in the 

 larger animals all things are more conspicuous ; in the more 

 perfect, they are also more distinct ; and in those that we can 

 command, and that live with us, everything is more readily 

 examined : we have it in our power so often as we please to 

 repeat our observations, and so to free them from all uncer- 

 tainty and doubt. Now, among oviparous animals of this de- 

 scription, we have the common fowl, the goose, duck, pigeon ; 

 and then we have frogs, and serpents, and fishes ; Crustacea, 

 testacea, and mollusca ; among insects, bees, wasps, butterflies, 

 and silkworms ; among viviparous creatures, we have sheep, 

 goats, dogs, cats, deer, and oxen ; lastly, we have' the most 

 perfect of all animals, man. 



Having studied and made ourselves familiar with these, we 

 may turn to the consideration of the more abstruse nature of 

 the vegetative soul, and feel ourselves in a condition to under- 

 stand the method, order, and causes of generation in animals 

 generally ; for all animals resemble one or other of those above 

 mentioned, and agree with them either generally or specifically, 

 and are procreated in the same manner, or the mode of their 

 generation at least is referrible by analogy to that of one or 

 other of them. For Nature, perfect and divine, is ever in the 

 same things harmonious with herself, and as her works either 

 agree or differ, (viz. in genus, species, or some other propor- 



