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frequent symptom in cattle, sheep and hens, (10, 12, 99, 101). An apparent
increase of the vitamin C content of the various organs of the cow has been
reported (93). Sheep and calves have been observed to become anæmic
and to exhibit photophobia (101, 107). Transitory glycosuria has been ob-
served in lambs (51), the coagulation time of the blood is believed to be in-
creased in the cow (92), decreased in poultry (68), and to remain unchanged
in pigs (101). The plasma phosphatase is considered to be increased in cows
(87), but the results of other observations with cows (37) and with sheep
(86) seem to be too variable to allow any generalization. Calcium retention
is reported to be increased in cattle (37), and to decrease (46, 82) or remain
stationery (56) in pigs. Phosphorus retention is considered to be unfavour-
ably influenced in cattle (37). Serum calcium has been reported to be lowered
in young chicks but not in mature poultry (60), and serum calcium and phos-
phorus have been found to remain unchanged in cows (37). Earlier eruption
of the permanent incisors has been observed in sheep (85) although the con-
trary has been noted in children (1, 72). Ingestion of fluorine has been
found to exert no effect on the kidney phosphates of chickens (60). Wool
production in sheep is not seriously affected (85). Chronic fluorosis has not
so far been found to have any specific effect on the reproduction of cows (39,
92, 95) or of pigs (44, 45, 68). The results of feeding hens with rock phosphate
containing fluoride on the hatchability of their eggs were uncertain (53).
TOXICITY OF FLUORINE FOR DIFFERENT ANIMALS
The amount of fluoride necessary to bring about toxic symptoms depends
on a number of factors, of which the nature of the compound, the duration
and mode of intake, the nature and amount of other dietary, constituents
and the species and age of the animal, are important. Many authors have
neither stated the daily fluorine intake of their experimental animals nor
reported data from which this may be computed, but it would seem that the
approximate minimum amount of fluorine as sodium fluoride or as rock
phosphate, which when ingested over a considerable period, will result in
the syndrome of chronic fluorosis, is, for the hen 70 mg. for the pig 10 mg.
for the cow 3 mg. and for the sheep 3 mg. fluorine per kg. body-weight
each day. Amounts too small to affect general health and productivity may,
nevertheless, induce dental symptoms and result in an increased fluorine con-
tent of the skeleton (13, 39, 85, 92). General symptoms appear in the rat
after the addition of 20 mg. fluorine per kg. per day, while dental changes
are brought about by as little as 1 mg. per kg. per day (108). Experiments
with pigs, calves and chickens (68, 82, 101) indicate that, for the production
of general symptoms, sodium fluoride and sodium fluorsilicate are the most
toxic source of fluorine ; rock phosphate and phosphatic limestone ; are slightly
less, while cryolite and calcium fluoride are the least toxic. A similar grading
of toxicity has been observed in laboratory animals (68, 108). From the
results of experiments with chickens, it would seem that the toxicity of a
definite concentration of fluorine in the ration decreases with increasing age
(11, 60).
The toxicity of fluorine ingested in solution appears to be greater than
when it is consumed in a solid state. Water containing about 0.5 mg. fluorine
has been found to be as toxic for sheep as rock phosphate mixed with the ration