X INTRODUCTORY OBSERVATIONS', 



nomena, and of the life of a favage animal, our 

 knowledge is limited indeed. — The original caufe 

 of exiftence is in the moft profound obfcurity ; 

 we are in the utmofl ignorance wjiy the offspring 

 of an animal aflumes a determinate figure ; why 

 the increment of one part is more rapid than 

 that of another ; and why the fize of the whole 

 is at laft confined within certain bounds. No fa- 

 tisfaSlory reafon has hitherto been affigned, why 

 the capacity of either fex to generate does not 

 arife until a certain age ;' for the very different 

 duration of geftation by different females, or 

 the variety in the time of incubation. And al- 

 though we contemplate the progrefs of a difeafe 

 that ends in death, it is feldom that we can either 

 tell what is the real origin of it, or the caufe why 

 exiftence ceafes. Mofl of the animals, which 

 have been the fubjed of obfervation, we have en- 

 deavoured to domeflicate, but thofe that roam in 

 the defert, dwell on lofty mountains, are hid in 

 the earth, or concealed in the receifes of the ocean, 

 are hardly known to us by name. — is there any 

 wonder, therefore, that fo many centuries have 

 palfed away, before the properties of beings, al- 

 mofl as minute as we conceive the particles of 

 matter, have been inveftigat^d ? 



The animalcula of infufions conllitute a ciafs 

 in the animal kingdom, on which the learning 



and 



