264 
Transactions of the Society. 
Dr. E. E. Andrew?, of Cambridge, Mass., read a paper on enamel 
formation before the Columbian Dental Congress at Chicago in 1894, 
in which he describes an appearance of fibres passing from the amelo- 
blastic layer of cells into the forming enamel. Dr. Andrews was the 
first to describe the fibres which form the organic matrix of enamel,, 
and to him must be given full credit for their discovery ; but he was 
entirely in error as to their origin and ultimate disposition. He 
thought these fibres had their origin in the stratum intermedium , or, 
possibly, in the connective tissue lying outside of the enamel organ 
proper. One does not always see these fibres passing from the amelo- 
blasts into the forming enamel. When we come to examine the 
structure of completely formed enamel, we shall see clearly why this 
is so. There is a great variety in the appearances of the organic 
basis of the enamel rods, and this variety in appearance corresponds 
perfectly with differences to be observed in the structure of the cyto- 
plasm of the ameloblastic cells. Occasionally the cytoplasm of the 
enamel-forming cells is seen to be composed of strings or fibres, some- 
times smooth, sometimes granular in appearance, and more or less 
connected with each other by lateral offshoots. More frequently,, 
however, the cytoplasm of the ameloblasts is seen to be arranged in 
sections, which sections are more or less globular in appearance, the 
body of the cell being composed of five or six of these globular sec- 
tions. The structure of these sections somewhat resembles that of the 
nucleus of the cells, i.e. it is spongiose in character, with radiating 
processes by means of which the sections are united to each other 
longitudinally in the same cell, and, not infrequently, laterally to 
those in adjoining cells. 
The cytoplasm of the cells, in both the fibrous and the sectional 
arrangement, is seen to be connected with the nuclei ; and, from a 
study both of the cells and of the completely formed enamel rods, we 
conclude that the substructure of the rods is simply the calcified 
cytoplasm of the cell ; the function of the ameloblasts is there- 
fore to supply this organic matrix or substructure into which the 
calcific material secreted by the cells of the stratum intermedium is 
deposited. 
The exact manner in which the formation of enamel is effected 
will be very clearly shown in figs. 5 and 6. For many years 
there have been two opposing theories as to the method of enamel 
formation. Some of you may remember the controversy between 
Professors Huxley and Carpenter on this subject, which extended 
over several years between 1850 and 1860. Prof. Carpenter 
attempted to show that enamel was produced by direct cell calcifica- 
tion, while Prof. Huxley maintained that it could not be so produced, 
and that it was the product of the secretion of the enamel organ. 
Most of the eminent anatomists of the last fifty years have stoutly 
defended one or other of these two theories. It now seems evident 
that each of these theories came very near expressing just half of the 
