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THE ENAMEL ORGAN. 63

Just within these two epithelial layers there is found the second im-
portant layer of cells, and this layer has been named the stratum inter-
medium (see Fig. 55). The cells of this layer are intermediate in shape

Fig. 44.

Section of jaw, embryo of pig, showing development of dental follicle and first stage in the growth
of the permanent enamel organ; also the formation of walls of the saceuhis : 1, epithelium
;
2, Malpighian layer ; 3, enamel organ ; 4, dentin germ ; 5, outer wall of sacculus ; 6, inner wall
of sacculus ; 7, bud of enamel organ of permanent tooth ; 8, growing jaw.
between the ameloblasts and those of the stellate reticulum. The layer
was first described by Hanover, and is thought to be a supplying and
nourishing layer to the ameloblasts. Over these they remain, while
everywhere else they disappear as calcification progresses. It is prob-
able that they give birth to new enamel cells as the circumference of the
enamel layer increases by growth. By careful examination it will be
found that they are connected by minute processes with the enamel cells
and also with the stellate cells of the central portion. Dr. Lionel Beale
first made the statement that a vascular network lies Avithin the stratum
intermedium. This fact has recently been confirmed by other English

they are completely lost some time before the comj)letion of the calcilication of the enamel.
Just after a layer of dentin has been formed, everywhere upon its surface are seen the
enamel cells, ready to form the enamel, and no trace of the outer epithelium can be seen.
It has disappeared from tliat part in the perfected enamel organ.