i 
Say THE CAUSES OF THE XI 
time when they each and all of them resemble 
this one of the dog. But as development 
advances, all the parts acquire their speciality, 
till at length you have the embryo converted into . 
the form of the parent from which it started. So 
that you see, this living animal, this horse, begins 
its existence as a minute particle of niGrOgSnOM 
matter, which, being supplied with nutriment 
(derived, as I have shown, from the inorganic 
world), grows up according to the special type and 
construction of its parents, works and undergoes a_ 
constant waste, and that waste is made good by 
nutriment derived from the inorganic world; the 
waste given off in this way being directly added” 
to the inorganic world. Eventually the animal 
itself dies, and, by the process of decomposition, 
its whole body is returned to those conditions 
of inorganic matter in which its substance 
originated, 
This, then, is that which is true of every living 
form, from the lowest plant to the highest atin : 
—to man himself, You might define the life of — 
every one in exactly the same terms as those 
which I have now used; the difference between ~ 
the highest and the siarest being simply in the ~ 
complexity of the developmental changes, the 
variety of the structural forms, and the diversity - 
of the physiological functions which are exerted - 
by each, 
If I were to take an oak tree, as a specimen of © 
a 
5 . 
ill al i MAT 
