TUBERCULOSIS.	227
plasm of the cells affected takes on a hyaline character,
and seems abnormally viscid, so that contiguous cells
have a tendency to become partially confluent. The
chromatin of their nuclei becomes dissolved in the nu-
clear juice and gives stained nuclei a pale but homo-
geneous appearance. Sometimes this nuclear change is
only observed very late. As the necrosis advances the
contiguous cells flow together and form large protoplas-
mic masses—giant-cells—which contain as many nuclei
as there were component cells. It may be that these
nuclei multiply by karyokinesis after the protoplasmic
coalescence, but only one observer, Baumgarteci, has
found signs of this process in giant-cells. While these
changes are in progress in the cells of the primary focus,
the leucocytes may collect in such numbers as to obscure
them and make themselves appear to constitute the prim-
itive cells. When the irritant substance is produced in
considerable quantities, the most delicate cells die first;
and it is not infrequent to find a tubercle rich in leuco-
cytes suddenly showing degeneration of these cells, with
recurring prominence of the original epithelioicl cells.
It has been taught by some that the giant-cells are
produced by the union of the leucocytes, but a careful
observation of the role played by these cells will convince
one that such an origin for these monstrous cells must be
very rare.
Giant-cells are not always produced, for sometimes the
necrotic changes are so violent and widespread as to con-
vert the whole cellular mass into a granular detritus of
tin recognizable fragments.
Tubercles are constantly avascular, as would be ex-
pected of a process which is a combination of progressive
irritation and necrosis. The avascularity may be a fac-
tor in the necrosis of the larger tuberculous masses, but
it plays no part in the degeneration of the smallest tuber-
cles, which is purely toxic.
Tubercles may be developed in any tissue and in any
organ. In whatever situation they occur, space is occtt-