310 ZOOLOGICAL PHILOSOPHY 



From these principles it follows : that all animals which have a 

 nervous system need not necessarily have a brain, since the latter is 

 characterised by the faculty of giving immediate rise to some sense, 

 at all events the sense of sight ; that all animals which have a brain 

 need not also have two wrinkled hemispheres, for the smallness of the 

 brain in the last six classes of invertebrates shows that it can only 

 serve for the production of muscular movement and feeling, and not 

 for acts of intelligence ; lastly, that all animals, whose brains are 

 provided with two wrinkled hemispheres, possess the power of muscular 

 movement and of feeling, the faculty of experiencing inner emotions, 

 and, in addition, that of forming ideas, making comparisons and judg- 

 ments and, in short, of carrying out various acts of intelligence, 

 corresponding to the degrees of development of the hypocephalon. 



On paying careful attention to the matter we shall feel that the 

 operations which give rise to thoughts, meditations, etc., occur in the 

 superior and anterior part of the brain, that is, in the two wrinkled 

 hemispheres. We can, moreover, make out that these operations are 

 not carried out either in the base of the brain, or in its posterior and 

 inferior part. The two cerebral hemispheres composing what I call 

 the hypocephalon, are therefore really special organs in which acts of 

 intelligence are produced. Thus when we are thinking and fix our 

 attention too long on one subject, we feel a pain in the head, especially 

 in the part that I have mentioned. 



It follows from these various principles that among animals which 

 have a nervous system : 



1. Those which have no brain, and consequently no special senses 

 nor single centre of communication for the nerves, do not possess 

 feeling but only the faculty of moving their parts by true muscles ; 



2. Those which have a brain and special senses, but not the wrinkled 

 hemispheres which constitute the hypocephalon, only derive two or 

 three faculties from their nervous system, viz. those of performing 

 muscular movements, of experiencing sensations, that is to say, simple 

 and fugitive perceptions when any object aifects them, and perhaps 

 also of experiencing inner emotions ; 



3. Lastly, those which have a brain together with its accessory 

 hypocephalon enjoy the capacity for muscular movement, feeling, 

 and emotion, and can moreover, by means of an essential condition 

 (attention) form ideas, which are impressed on the organs, compare 

 these ideas together, and produce judgments ; and if their hemi- 

 spheres are developed and perfected, they can think, reason, invent, 

 and perform various intelligent acts. 



No doubt it is very difficult to imagine how the impressions are 

 formed that correspond to ideas ; nothing whatever can be seen to 



