302 Chronic Fluorine Intoxication in Domestic Animals.
symptom of chronic fluorosis, has been reported to be endemic in India, China
and Japan. These latter indications have occurred after local volcanic erup-
tions, or in the neighbourhood of chemical industries which utilise materials
containing fluorine ; at times the water supply has been incriminated.
In very early records, dated 1,100 A.D., attention was called to a disease
of domestic animals, particularly of grazing sheep, which generally appeared
after the periodic volcanic eruptions that have been an important feature
of the history of Iceland (99).
This disease has been more fully described in the records of an outbreak
subsequent to the 1845 eruption of Hekla. While many animals died of acute
poisoning with a few weeks of this disturbance, the majority suffered no
apparent trouble until the following year, when symptoms of emaciation,
decreased milk yield, weakness and impairment of the use of the limbs, thick-
ening of the joints and the development of exostoses of the long bones and
of the jaws became apparent. Young animals suffered most. Mottling of
the teeth with selective abrasion of the molars and pitting of the incisors, were
also described. All but the dental symptoms were reported to subside if
the animals were confined in barns and fed on hay produced prior to the erup-
tion. The skeletal changes, which are now generally accepted to be typical
of chronic fluorine poisoning, have since been recongised by Roholm in museum
collections of material preserved since the 1845 outbreak (99).
Mottling of the enamel of the teeth of domestic animals is also common
in certain areas both in North and South America (30, 31, 40), and amongst
the human population in regions of the U. S. A. where the drinking water
contains relatively large quantities of fluorine (30, 31). In districts in the
Argentine, where the drinking water contains approximately 10 mg. fluorine
per litre, a high incidence of dental abnormality both in human beings and in
horses has been described, and while the molars of cattle in these areas ap-
peared sound, they are reported to show histological lesions similar to those
associated with macroscopic mottling (40). Mottled enamel of the incisors
an excessive wear of the molars have also been described in man, cattle
and horses in Modoc County, California (57).
The malady, Darmous, which occurs among human beings, horses, cattle
and sheep in places in Algeria, Morocco and Tunis has been shown to be
due to poisoning by fluorine (48, 115). The most obvious manifestations
are the dental abnormalities which occur in animals which have lived conti-
nuously in the affected regions. Bone lesions are also apparent. The mandible
becomes thickened either by isolated exostoses or by a diffuse covering of
periosteal bone (14), and spontaneous bone fractures occur among affected
horses and mules (115). The teeth of affected animals are modified in colour,
size, orientation, shape and structure. Reduction in hardness results in pit-
ting of the incisors and selective abrasion of the molars. In horses, the tem-
porary teeth are at times affected (117). The growth of cattle horses and
mules in these areas is seriously impaired, but sheep seemingly are not
seriously affected in this way (118). Velu (115) has demonstrated that all
symptoms of the malady may be induced in rats and sheep either by giving
Algerian or Moroccan rock phosphate or calcium fluoride, or by supplying
the animals with drinking water in which the fine rock phosphate dust con-
taining fluorine had been suspended or which had been in contact with the