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creep, and swim; those that are by nature nocturnal, and 
such as are diurnal ; those that hybernate, those that do not ; 
and some of which it is doubtful whether or not they ever 
sleep. Let us also allude to such phenomena as compensatory 
functions ; the repair in some animals, the reproduction in 
others, of injured portions of their bodies ; the development of 
some such portions under particular conditions, the atrophy 
of others. In regard to each of these, phenomena of life and 
functions are special, not only in species, but in individuals, 
and on occasions different according to period of the year, as 
well as in seasonal and meteorological changes. Therefore 
deductions drawn can have reference only to the particular 
individual and circumstances on and under which they are 
arrived at. This enumeration could easily, by its length, be 
made tedious, if it is not so already. But to assert that any 
one of those alluded to has either ascended or descended from 
any other, is to adduce as fact that which remains within the 
sphere of the conjectural. 
On the present subject a well-known London physician has ex- 
pressed himself after this manner*: — The changes which occur 
in every organic structure as years roll on are to be considered 
normal. They are in harmony with the dictates of nature ; they 
are no more unnatural than the sere and yellow leaf which falls 
from the oak in autumn. Why one creature should live longer, 
or burn out sooner than another, is not clear ; why tissues of 
the same composition should wear out in one animal after ten 
revolutions of the earth, when it takes a hundred revolutions 
to destroy similar ones in another, is by no means apparent. 
Why, for example, should a dog be worn out in ten or twelve 
years, its limbs stiff, its sight and hearing impaired, its intel- 
lect obtuse, and senile changes be discoverable in its brain 
and elsewhere, when a parrot may take a century for the pro- 
duction of the same destructive changes ? To these, and to 
thousands of questions pertaining to the same category, not- 
withstanding all the investigations dictated by science, pursued 
throughout a score of centuries, all we can yet say in expla- 
nation is, Nature wills it so, and so it is. And the reply, 
precisely similar in purport, is considered to have been given 
centuries before our era dawned. Opinion has meantime 
oscillated from one extreme to another extreme ; at one time 
obscured by a tide of credulity and superstition, at another by 
a flood of scepticism, doubt, and materialistic teaching ; the 
absolute result in regard to these and many other questions 
relating to the nature and source of life that the investiga- 
* See Lancet , August 6, 1881, p. 223. 
