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TEE POPULAR SCIENCE MONTELY.— SUPPLEMENT. 



Even these relations are not invariable, for we 

 find exactly the opposite arrangement in birds ; 

 their motor cells are triangular and their sensi- 

 tive cells quadrangular. Thus we see that these 

 forms are really of very little importance, and 

 very plainly in this case we cannot infer function 

 from structure. But, on one hand, the geometri- 

 cal form must not be confounded with the me- 

 chanical arrangement, and, on the other, struct- 

 ure itself must be distinguished from the fact of 

 adaptation. Thus, whatever the shape of the 

 nerve-cells may mean, and though it may have 

 no relation with a given function, the fact re- 

 mains that the nerves must have such an ar- 

 rangement that they can put the centre into 

 communication with the organs, and, through 

 them, with the external medium ; therefore, this 

 disposition of convergence and divergence from 

 the parts to the centre, and from the centre to 

 the parts, is in manifest relation with sensation 

 and locomotion, which are no less plainly related 

 to the preservation of the animal. Besides, even 

 supposing that the structure itself has no signifi- 

 cation, the fact of adaptation exists none the 

 less. For instance, I do not know whether the 

 structure of the salivary glands and that of the 

 mammary glands have some kind of relation or 

 not with the particular secretions produced in 

 these two kinds of organs ; but even if there 

 were no such relation whatever, not the less does 

 the fact of salivary secretion hold a very strik- 

 ing relation of adaptation and agreement with 

 the function of nutrition ; and so, too, not the 

 less, the secretion of milk, which occurs only at 

 the time when it is useful, and by a fortunate 

 coincidence with the act of parturition, presents 

 the most remarkable adaptation and the most 

 surprising agreement with the final result, which 

 is the preservation of the young. 



Besides, it is not at hap-hazard that organized 

 substance passes from that first homogeneous, 

 amorphous, indefinite state, which seems to be 

 its start, into that state of skillful complication 

 in which it shows itself in the higher animals : 

 it docs this according to a law, the law of pro- 

 gressive improvement of the functions in propor- 

 tion to the progressive differentiation of the or- 

 gans. This is the law that Milne-Edwards neatly 

 calls the law of the division of labor, and he 

 points out its high importance in the progressive 

 development of animal nature. The very expres- 

 sion of this fortunate formula shows how very 

 difficult it is for science to escape that compari- 

 son between man's work and Nature's work, so 

 evident is it that these two kinds of work are 



only degrees of one and the same fact. This law 

 makes one more resemblance between the two 

 sorts of industry. With humanity, indeed, all 

 needs, all functions, are at first in a manner min- 

 gled together. The only difference of functions 

 is that which in each individual results from the 

 difference of organs and needs. Thus the first 

 division of labor is that which Nature herself 

 prescribes ; but in proportion as wants multiply, 

 the actions and functions of individuals get apart, 

 and the means of performing these different ac- 

 tions more conveniently and usefully for man 

 multiply in turn. Thus human industry is noth- 

 ing more than the extension and unfolding of 

 Nature's industry. Nature makes prehensile or- 

 gans, arms and hands ; industry enlarges these 

 by means of picks, sacks, sticks, pails, and all 

 implements for digging, felling, drawing water, 

 mining, etc. Nature makes organs for triturat- 

 ing food ; industry extends them by contrivances 

 serving to cut, tear, dissolve these elements in 

 advance by fire, water, and salts of all kinds, and 

 the culinary art becomes, as it were, the supple- 

 ment to the digestive art. Nature gives us or- 

 gans of movement which are themselves wonders 

 of mechanism, compared with the rudimentary 

 organs of mollusks and zoophytes ; man's indus- 

 try enlarges and multiplies these locomotive ap- 

 pliances by all the motor machines, and by ani- 

 mals used as machines. Nature gives us pro- 

 tective organs ; we add to them by the use of 

 skins of animals, and by all machines employed 

 to prepare these. Nature, to conclude, gives us 

 the organs of sense, and human industry aug- 

 ments them by numberless instruments made on 

 the same principles as the organs themselves, 

 and used as means either for repairing the weak- 

 nesses and exhaustion of our organs, or for en- 

 larging their range and improving their use. 



We constantly contrast Nature with art, as if 

 art itself were not a thing of Nature. How are 

 cities built by man at all less natural than beav- 

 ers' huts and bees' cells ? In what are our cra- 

 dles less natural than birds' nests ? our dress less 

 natural than silk-worms' cocoons ? or the singing 

 of our artists less natural than the song of birds ? 

 If there be any opposition between man and Na- 

 ture it is in the moral order, in the order of free- 

 dom and right, and in the religious order too; 

 but in the domain of art and industry man acts 

 as a natural agent ; human industry is nothing 

 more than the extension, the continuation, of 

 Nature's industry, man doing consciously what 

 Nature theretofore did by instinct. Reciprocally 

 then we may say that Nature, in passing from the 



