1894. | 389 [ Poulton® 
has been applied to the tooth, so has the tooth grown. But 
would pressure produce such an effect upon a tooth? That is 
certainly not our experience. Pressure and friction have an 
unfortunate way of wearing a hole in the tooth, rather than 
causing it to grow an elevation. As a matter of fact we know 
that the shape of teeth is predetermined long before they are cut 
in the soft dental matrix beneath the gum. It is not a question 
of the transmission of acquired characters, but the supposed 
transmission of a character which the parent cannot by any means 
acquire. ‘Teeth, so far as they react to pressure or friction can 
only react by wearing away. With regard to the joint, we are 
told by some Lamarckian writers, that pressure and friction pro- 
duce the reverse effect and wear away cavities rather than cause 
new growth. 
I was reading a most interesting paper by Dr. Wortman of 
New York, the other day, attempting to explain the occurrence 
of a furrow in a joint, owing to the pressure of a corresponding 
ridge. The pressure of the ridge, it was said, produces a furrow 
in the opposite side of the joint. It seems to me that in this we 
are going a little beyond what physiology and histology teach us. 
It seems to me to be a blind appeal to mechanical forces unsup- 
ported by any adequate investigation of the physiology and _ his- 
tology of the tissues concerned. Is it likely that a bone would 
react to intermittent pressure by producing a furrow? It is far 
more probable that the reverse effect would tend to be produced. 
I will only ask one more question with regard to this matter of 
use and disuse, and that is, why, if you are going to explain any 
of these parts by pressure and friction, should the process be 
stopped when a useful level is reached? If the pressure does 
cause such effects and they are hereditary, how are they prevented 
from increasing beyond all bound in the course of generations ? 
Why should pressure on teeth cease to produce further growth, 
when the tubercle has reached its proper height? It seems to me 
that the fact that all these shapes of bones and teeth just reach 
and stay at an adaptive level is the strongest evidence that they 
are not produced by the operation of mechanical forces, but by 
natural selection. - 
We now pass to the consideration of indirect evidence: that it 
would be impossible to explain evolution without the Lamarckian 
theory. 
