INTRODUCTION. If) 



inclosed by the skin of tire tadpole ; and the tadpole, to become a frog, 

 parts with its tail, mouth, and branchias. The child, at its birth, loses its 

 placenta and membranes ; at a certain period its thymus gland nearly dis- 

 appears, and it gradually acquires hair, teeth, and beard ; the relative size 

 of its organs is altered, and its body augments in a greater fatio than its 

 head, the head more than the internal ear, &c. 



The place where these germs are found, and the germs themselves are 

 collectively styled the ovary; the canal through which, when detached, 

 they are carried into the uterus, the oviduct; the cavity in which, in many 

 species, they are compelled to remain for a longer or shorter period pre- 

 vious to birth, the litems; and the external orifice through which they 

 pass into the world, the vulva. Where there are sexes, the male impreg- 

 nates the germs appearing in the female. The fecundating liquor is 

 called semen; the glands that separate it from the blood, testes; and when 

 it is requisite it should be carried into the body of the female, the intro- 

 ductory organ is named a penis. 



Of the Intellectual Functions of Animals. 



The impression of external objects upon the me, the production of a 

 sensation or of an image, is a mystery into which the human understand- 

 ing cannot penetrate ; and materialism an hypothesis, so much the more 

 conjectural, as philosophy can furnish no direct proof of the actual exist- 

 ence of matter. The naturalist, however, should examine what appear to 

 be the material conditions of sensation, trace the ulterior operations of the 

 mind, ascertain to what point they reach in each being, and assure himself 

 whether they are not subject to conditions of perfection, dependent on the 

 organization of each species, or on the momentary state of each individual 

 body. 



To enable the me to perceive, there must be an uninterrupted commu- 

 nication between the external sense and the central masses of the medul- 

 lary system. It is then the modification only experienced by these masses 

 that the me perceives : there may also be real sensations, without the ex- 

 ternal organ being affected, and which originate either in the nervous chain 

 of communication, or in the central mass itself; such are dreams and vi- 

 sions, or certain accidental sensations. 



By central masses, we mean a part of the nervous system, that is so 

 much the more circumscribed, as the animal is more perfect. In man, it 

 consists exclusively of a limited portion of the brain ; but in reptiles, it 

 includes the brain and the \vhole of the medulla, and of each of their parts 

 taken separately, so that the absence of the entire brain does not prevent 

 sensation. In the inferior classes this extension is still greater. 



The perception acquired by the me, produces the image of the sensation 



