ADDRESS. iil 
one nerve-fibre differed from another in the very essence of its work. It was 
just about the end of the past century, or the beginning of the present 
one, that an English surgeon began to ponder over a conception which, 
however, he did not make known until some years later, and which did 
not gain complete demonstration and full acceptance until still more years 
had passed away. It wasin 1811, in a tiny pamphlet published privately, 
that Charles Bell put forward his ‘New Idea’ that the nervous system was 
constructed on the principle that ‘the nerves are not single nerves possess- 
ing various powers, but bundles of different nerves, whose filaments are 
united for the convenience of distribution, but which are distinct in oftice 
as they are in origin from the brain.’ 
Our present knowledge of the nervous system is to a large extent only 
an exemplification and expansion of Charies Bell’s ‘New Idea,’ and has 
its origin in that. 
If we pass from the problems of the living organism viewed as a 
machine to those presented by the varied features of the different crea- 
tures who have lived or who still live on the earth, we at once call to 
mind that the middle years of the present century mark an epoch in 
biologic thought such as never came before, for it was then that Charles 
Darwin gave to the world the ‘ Origin of Species.’ 
That work, however, with all the far-reaching effects which it has had, 
could have had little or no effect, or, rather, could not have come into 
existence, had not the earlier half of the century been in travail preparing 
for its coming. For the germinal idea of Darwin appeals, as to witnesses, 
to the results of two lines of biologic investigation which were almost 
unknown to the men of the eighteenth century. 
To one of these lines I have already referred. Darwin, as we know, 
appealed to the geological record ; and we also know how that record, 
imperfect as it was then, and imperfect as it must always remain, has 
since his time yielded the most striking proofs of at least one part of his 
general conception. In 1799 there was, as we have seen, no geological 
record at all. 
Of the other line I must say a few words. 
To-day the merest beginner in biologic study, or even that exemplar 
of acquaintance without knowledge, the general reader, is aware that 
every living being, even man himself, begins its independent existence as 
a tiny ball, of which we can, even acknowledging to the full the limits 
of the optical analysis at our command, assert with confidence that in 
structure, using that word in its ordinary sense, it is in all cases absolutely 
simple. It is equally well known that the features of form which supply 
the characters of a grown-up living being, all the many and varied features 
of even the most complex organism, are reached as the goal of a road, at 
times a long road, of successive changes ; that the life of every being, from 
the ovum to its full estate, is a series of shifting scenes, which come and 
go, sometimes changing abruptly, ‘sometimes melting the one into the 
