294 ZOOLOGICAL PHILOSOPHY 



of any common nucleus that is essential to the production of feeling ; 

 they consider feeling to be an attribute of all the nerves, including even 

 their smallest parts ; and, to strengthen their view as to the absence 

 of any centre of communication in the sensitive system, they allege 

 that the need for finding a definite situation for the soul has caused 

 the invention of this common nucleus or circumscribed locality to 

 which all sensations are conducted. 



It is quite enough to believe that man possesses an immortal soul ; 

 there is no occasion for us to study the seat and Umits of this soul 

 in the individual body, nor its connection with the phenomena of 

 organisation : all that we can ever say on this subject is baseless and 

 purely imaginary. 



If we are studying nature she alone should occupy our attention ; 

 and we should confine ourselves exclusively to the examination of the 

 facts which she presents, in our endeavour to discover the physical 

 laws which control the production of these facts ; lastly, we ought 

 never to introduce into our theories any subjects that are outside 

 nature, and about which we shall never be able to know anything 

 positive. 



For my own part, I only study organisation in order to arrive at an 

 understanding of the various faculties of animals. I am convinced 

 that many animals possess feehng, and that some of them also have 

 ideas and perform intelhgent acts ; and I hold that the causes for these 

 phenomena should be sought in purely physical laws. I always make a 

 rule of this in my own researches, and I may add that I am not only 

 convinced that no kind of matter can in itself possess the faculty of 

 feeUng, but I am also convinced that this faculty in such hving bodies 

 as possess it consists only in a general effect which is set up in an 

 appropriate system of organs, and that this effect cannot occur unless 

 the system possesses a single nucleus or centre of communication, 

 in which terminate all the sensitive nerves. 



In the case of vertebrates, it is at the anterior extremity of the spinal 

 cord, in the medulla oblongata itself or perhaps its annular protuber- 

 ance, that the sensorium commune is lodged ; that is to say, the centre 

 of communication of the nerves which give rise to the phenomenon 

 of sensibility ; for it is towards some point at the base of the brain 

 that these nerves appear to converge. If the centre of communication 

 were farther forward in the interior of the brain, acephahc animals, 

 whose brain had been destroyed, would be devoid of feeling and 

 imable even to Uve. 



But this is not the case : in animals which possess any faculty of 

 intelligence, the nucleus for feeling is confined to some part of the base 

 of what is called their brain ; for this name is given to the entire 



