86 FEATHERS. 
tema of the cells of the pith of the feather is supplied by the 
nearest contiguous substance provided with vessels, that is, by 
the so-called matrix. In the young feathers of the hen, how- 
ever, [ found a layer of very small, extremely pale, round cells 
without nuclei,—a sort of imperfect epithelium,—between 
the matrix and the granulous cytoblastema, so that not even 
so much as an immediate contact exists between the latter and 
the organized substance. 
The cortical substance of the shaft of the feather is a 
fibrous structure. Here the Cell-theory seems, at first sight, 
to fail; but we are soon taught otherwise, when we examine | 
the generation of the fibres as exhibited in the completely 
formed portion of the cortical substance of a feather, which 
is in progress of formation within the capsule. The cortex 
is then seen to consist of large flat epithelium-cells, each 
having a beautiful nucleus, with one or sometimes two 
nucleoli. Some of these epithelial tables are long fiat stripes, 
others are of an irregular rhomboidal form. They are very 
firmly connected together. Hach cell generates several fibres, 
and the transitions may be readily observed at different 
parts of the same preparation. Plate II, fig. 13, represents 
them. The cells at first are flat tables, having a smooth 
margin, a slightly granulous aspect, and containing a very dis- 
tinct nucleus (fig. 13, a). Upon their margins and sur- 
faces indistinct fibres gradually become visible, which project 
out insulated from the edges, but are connected together upon 
the surface by the substance of the tables (fig. 13, 0). At 
this stage the fibres are pale, and the nucleus of the cell still 
quite visible. ‘The fibres afterwards become more sharply and 
darkly defined; the imsulated portions projecting from the 
edges are larger, the part of the table connecting them together 
becomes more indistinct, and the nucleus begins to wane, 
although it is still distinctly perceptible, and the nucleolus 
especially so (fig. 13, ec). At length all traces of the original 
cell and the nucleus disappear, and we see only dark, stiff, 
thin fibres, which are closely connected together but may 
still be recognized as being insulated for a space, the length of 
the original table (fig. 13, d). These fibres, therefore, also 
originate from cells, and that not so much by an elongation 
of the cells, as by their division into several fibres. As the 
