304 ZOOLOGICAL PHILOSOPHY 



possess this system of organs ; whence it follows that those which 

 have not got it can enjoy none of the faculties which it produces. 



When people have said that, in animals without nervous threads 

 (such as the polyps and infusorians), the medullary substance which 

 yields sensations was distributed and dissolved in every part of the body, 

 instead of being collected into threads ; and that from this it followed 

 that each fragment of these animals became an individual endowed 

 with its particular ego ; they have probably paid no attention to the 

 invariable characteristic organic function, which is always due to 

 relations between the containing parts and contained fluids, and to 

 the movements resulting from these relations. There was no adequate 

 knowledge of the essential facts with regard to the functions of the 

 nervous system ; it was not known that these functions only worked 

 by causing the movement or transport of a subtle fluid, either from a 

 nucleus towards the parts or from the parts towards the nucleus. 



The nervous system cannot then exist, nor fulfil the least of its 

 functions, unless it consists of a medullary mass with a nucleus for 

 the nerves, and also of nervous threads which run into this nucleus. 

 Moreover the medullary matter, or any other animal substance, cannot 

 possess in itself the faculty of producing sensations, as I hope to prove 

 in the third chapter of this part ; hence this medullary substance 

 when dissolved as alleged in every part of an animal's body would not 

 give rise to feeling. 



If the nervous system at its greatest simplicity is necessarily com- 

 posed of two kinds of parts, viz. a main medullary mass and nervous 

 threads running into it ; we may feel how great was the progress 

 required in the complexity of animal organisation, starting from the 

 Monas, which is the simplest and most imperfect of known animals, 

 before nature could have attained the formation of such a system of 

 organs even in its greatest imperfection. Yet when this system begins, 

 its complexity and perfection are still very far from what we find in 

 the most perfect animals ; and before it could begin, animal organisa- 

 tion had already made much progress in development and complexity. 



To convince ourselves of this truth, let us examine the products of 

 the nervous system at its chief stages of development. 



The Nervous System in its Simplest State produces 

 nothing but muscular movement. 



I have, it is true, nothing more than a mere opinion to offer on this 

 subject ; but it is based on considerations of such importance and 

 weight that it may at least be regarded as a moral truth. 



If the procedure of nature is attentively examined, it will be seen 

 that in the creating or giving existence to her productions, she has 



