LAW OF ASSOCIATION IN THE ANIMAL KINGDOM. 
31 
most perfect, and seeking among them not differences but 
relationships, it seemed to me that a simple and very general 
law had presided over their formation ; that they were derived 
one from the other by a constant process ; and I found that I 
had added some additional arguments to the theory of the 
genealogical relationship of species. 
The law which I now have to put forward may be designated 
the law of association. The process by which it has produced 
the greater number of organisms is the transformation of societies 
into individuals. 
From the day when it was proved that every living 
-creature was composed of microscopic corpuscles more or less 
resembling each other, from the day when it was seen that 
similar corpuscles capable of leading an independent existence 
constituted of themselves the simplest organisms, it has been 
thought that we might compare the highest animals and plants 
to vast associations of distinct individuals, each represented by 
one of these living corpuscles, one of these cells , to use the 
term adopted by anatomists. In the same animal the cells may 
display a great number of forms and different physiological 
properties. These forms and properties are not in the least 
degree modified by the vicinity of different cells. In the 
very heart of an organism each cell lives as if it were alone — 
that is to say, if it were possible to isolate a cell from the human 
body and to place it in a nutritive medium like that which 
normally surrounds it, that cell would continue to live, to 
obtain nourishment, to develope and reproduce itself : in a 
word, it would exercise all its physiological functions precisely 
as before. But more than this ; in the organism itself the life 
of each cell is so independent of that of its neighbours that it 
is possible to kill all the cells of the same kind without 
affecting the others. Claude Bernard has demonstrated that 
curare poisons the elements which terminate the motor nerves, 
thus abolishing all movement, without in the least injuring the 
other parts of the nervous system, and, in particular, leaving 
sensibility absolutely intact. It was in consequence of his 
investigations upon curare that he asserted, more distinctly than 
had ever been done before, the principle of the independence of 
the anatomical elements. 
Thus, in organisms, not only are the elementary individuals 
sometimes very dissimilar, but in spite of the bonds which unite 
them, they retain all their personality. We may therefore 
compare an animal or a plant to a populous city in which flourish 
numerous corporations, the members of which, each on his own 
account, practise some particular art or industry, and yet 
contribute to the general prosperity through the activity of the 
exchanges which occur throughout ; in the higher organisms a 
I 
