550 General Notes. 
backwards and downwards, while the apices of the lower molars 
slope forward and upward, just as they do in the adult, yet at this 
stage there has been no enamel or dentine formed. This fact shows 
that the forms of the crowns are foreshadowed in the germs of the 
teeth before calcification, and it now becomes possible to assume, 
for the first time with a reasonable show of -probability, that this 
forward and rearward deflection of the molars is due to an inherited 
impress or modification induced by the characteristic mode in which 
the grinding teeth were used in the Rodentia. Because it may be 
assumed that the manner in which the teeth are used would slowly 
affect pattern of the crowns, as the writer first tried to show in his 
essay “ On the mechanical genesis of tooth-forms” (Proc. Acad. 
Nat. Sci. Phila., 1878). It follows that if physiologically induced 
mutilations may be inherited, as the results of Von Brunn seem to 
demonstrate, it is almost equally certain that mechanically induced 
changes of form slowly caused by the normal mode in which the 
teeth were used could be inherited with probably even greater 
readiness. 
Dr. W. Xavier Sudduth has shown that the reticulum of the 
enamel organ becomes thinner at the apex of the young tooth. In 
this way he has also shown that the membrana adamantina or inner 
tunic and outer tunic are approximated while the blood vessels 
from the adjacent connective tissue are pushed toward the enamel 
organ to supply it with nutriment and probably aid very considera- 
bly in the rapid deposit of the enamel from above, in just the same 
way as‘the vascular pulp would supply the conditions for the rapid 
deposition of the dentine from below. That the enamel organ of 
the foetus is supplied by a vascular plexus as assumed by Sudduth 
is, I think, completely demonstrated by the fact that I find a fine 
vascular plexus in immediate external contact with the persistent 
enamel organ of the incisor teeth of the adult white mouse. 
The great value which is to be attached to the fact that abrasions 
of the enamel of the adult, which have reacted upon the funtion 
activity of the enamel organ of the embryo rat, so that such 
mechanically induced alterations could be inherited, does not con- 
so roo a 
n appealed to as proving that mutilations could be inherited are 
without exception artificial; in the remarkable example of the 
already abraded apices of the molars of young mice and peng 
ot & 
This datum, which has until now been wanting, is therefore at last 
ble proof of the soundness of its principles. This datum, in a 
