66 PROF. LIONEL §. BEALE, F.R.C.P., F.R.S., ON VITALITY. 
remains the same enamel in the tooth of the adult. After 
enamel has been formed it is not ‘‘replenished ” or renewed 
at any time. Or to take a still more striking instance—the 
tusk of the elephant; the whole of the tusk of this huge 
creature was In the early stage of its development and 
growth structureless, consisting entirely of clear, soft, 
colourless living matter. Indeed, if you were to examine 
the part near to the soft, highly vascular living tooth-pulp 
of the full-grown animal you would find in what originally 
were the so-called “cells,” really in the form matter of 
the bioplasts, that minute particles of imorganic earthy 
matter were being gradually deposited, and as _ these 
increase, the soft living matter is slowly converted into a 
matrix which when impregnated with calcareous matter 
becomes the hard ivory. The outer oldest portion of the 
tusk of a living growing elephant may weigh 70 or 80 lbs., 
which in an old animal is non-living, though, of course, it is 
very firmly connected with the socket and the remainder of 
the ‘‘pulp” on the surface of which the continuous growth 
tukes place. The greater part of the ivory of the tusk of 
an elephant one hundred years old is as dead, though the 
base is still firmly connected with{the living animal, as 
when, long afterwards, part of it has been converted into 
bilhard balls which may last for many years without 
perceptible change. 
Connexion and disconnexion with the living body does 
not determine whether a given texture onght to be con- 
sidered living or dead, but the fact of any matter being 
alive is proved by its “growth,” a living process. The living 
matter which manifests this power of growth is invariably 
colourless, structureless, soft, and sometimes diffluent from 
the large quantity of water present in all matter that is 
alive, living matter that grows and changes quickly often 
containing more than 90 per cent. of water. 
[The lecturer then explained his drawings and diagrams 
to the audience. ] 
Discussion. 
The Cuairnman.—We shall be very glad to hear some remarks on 
this very interesting paper. It is one of the most fascinating 
subjects we can have to deal with, as well as one of the most 
difficult, if not the most difficult. 
