206
Pathology and Pathogenesis of Experimental Fluorosis in Cattle
Eosino. and Baso. 0 per cent and Mono. 0.5
per cent.
Hill bull No. 89
Five years and eight months, feed basal diet
alone for nine months.
Clinical. The animal showed no signs of
abnormality and no exostoses on any of the long
bones.
Blood picture. Rbc. 6.5, Wbc. 8.5, Hb. 11.9,
Lympho. 53.8 per cent, Neutro. 30.5 per cent,
Eosino. 10.2 per cent, Baso. 0.25 per cent, and
Mono. 5.25 per cent.
GROSS PATHOLOGY
The osseous changes under this heading may
be considered as common to all animals of the
'High Fluorine Group'. After maceration, all
bones appeared whiter than normal, and the
exostoses porous on close examination. None of
the bones could be cut with a knife, but some,
when tested with a saw yielded more easily to
a depth corresponding to the thickness of the
exostoses. The periosteum over the exostoses
appeared to be thickened, closely adherent to
the bone and markedly
hyperaemic.
The
marrow was gelatinous and contained reddened
patches and dilated capillaries, this feature being
more marked in the metaphyses. On longitudi-
nal section of the femur, the compacta revealed
an irregular thickness and isolated areas (Plate
XVI, fig. 1) of esorbed bone. Sections of bone
across the exostoses revealed the latter as
sharply defined areas, whiter in colour than
normal compacta, from which it was clearly
demarcated by a line (Plate XVI, fig. 2) and
could often be detached during sawing. Gen-
erally, the cut surface of the compacta appears
smooth, but in areas showing active periosteal
growth, the cut surfaces reveal 'islands' of
slightly hyperaemic soft tissue,
presumably
residual masses of periosteum entrapped due to
their inability to keep pace with the growing
exostoses.
The metaphyses were composed of a smaller
number of loose and thin trabeculae enclosing
wide spaces containing rather little hyperaemic
marrow.
The epiphyseal cartilages were wavy
in outline and irregular in width. Long bones
without palpable exostoses during life revealed
thickened subperiosteal tissue which had been
transformed into a white granular layer, repre-
senting the early stages of an exostosis.
On longitudinal section of the costal epiphysis
the cartilaginous junction appeared as an irregu-
lar line with tongues of cartilage projecting into
the subchondral spongiosa.
HISTOPATHOLOGY
Pieces of bone, 2-3 mm. thick, were fixed in
5 per cent neutral formol-saline, decalcified in
5 per cent nitric acid in 60 per cent alcohol
followed by washing in 70 per cent alcohol.
The tissues were then passed through chloro-
form to paraffin,
according to the technique
given by Kolin [1942]. In some cases exos-
toses and costal epiphyses were examined with-
out decalcification by the method of Thomas,
Clark and Schulz [1940], followed by staining
by V, Kossa's method or its modification by
Moolman [1941].
For histological work the lesions selected
were those on the metatarsal and metacarpal
bones, the epiphysis and diaphysis of the rib
and the distal extremity of the femur.
A des-
cription more or less common to all the three
fluorosis cases is given.
Metacarpus and metatarsus
Cross sections at the level of the exostosis usual-
ly revealed three well-defined zones (Plate XVII
fig. 1), the innermost corresponding to the old
compacta, the middle to the exostosis and the
outermost to the periosteum. Microscopically,
the exostosis was found to be composed of a
mesh-work of trabeculae arising from the outer-
limit of the old compacta.
The portion of
exostosis, adjacent to the old compacta, was
more compact in appearance, and the trabe-
culae for the most part better calcified with
well-developed osteocytes and only thin osteoid
borders. The part of the exostosis towards the
periphery, on the other hand, looked more
spongy, the trabeculae being arranged more
irregularly with wider spaces between them and
consisting of poorly calcified axes and wider un-
calcified osteoid tissues on either side. The
faulty nature and the poor degree of calcifica-
tion of the trabeculae in this part were revealed
by V. Kossa's method as irregular black-
stained masses of calcium scattered through the
matrix (Plate XVIII, fig. 1).
These seldom
coalesced to form one continuous black colour as
in normal bone. The osteoid tissues were lined
by a single layer of osteoblasts, and similar cells
were found on the surface of the
calcifying
osteoid tissues, although the latter also con-
tained osteocytes. The residual masses of peri-
osteum in the growing exostosis showed ossi-
fication (Plate XVII, fig. 2) by metaplasia
This was apparently brought about by the
formation of numerous acidophilic masses
which later coalesced to form trabeculae lined
with osteoblasts arising from the periosteal