_Toxic Principle._ Very little appears to be known about the poisonous principle, but, like _Rhinanthus_ and _Melampyrum_, they have been found to contain the glucoside _Rhinanthin_ (see p. 96).
_Symptoms._ The plants are held to be emetic and purgative; to cause inflammation of the digestive tract, and to cause anæmia in cattle. Brugmann stated (_vide_ Cornevin) that if, pressed by hunger, animals eat _P. palustris_, the first consequence is hæmaturia. Müller also notes hæmaturia.
=Docks= (_Rumex_ sp.). In general it is probable that but little harm is done by species of _Rumex_, but owing to the fact that Common Sorrel (_R. Acetosa_ L.) and Sheep’s Sorrel (_R. Acetosella_ L.) contain acid oxalates they may on occasion prove injurious. Instances have been recorded in which children have suffered from eating the leaves of the former species in considerable quantity, and both species have been accused by veterinary surgeons of poisoning horses and sheep, some sheep even dying. Pammel states that the Curled Dock (_R. crispus_ L.) induces nausea, watery brown fæces, copious urination, dry spasmodic cough, and perspiration; but no record of the death of animals has been found.
In regard to _R. Acetosella_ it is stated that in the _horse_ a condition may be produced resembling drunkenness, with vacillating gait, salivation, muscular tremors, dilatation of pupils, relaxation of sphincters, and a feeble, slow, and intermittent pulse: then convulsive contraction of lips, retraction of the eyeball, accelerated and stertorous breathing, extreme dilatation of the nostrils, tetanic contraction of the muscles of the neck, back, and limbs, abundant sweating and falling. In bad cases after a period of extreme exhaustion, these symptoms are repeated, and death occurs in convulsions (Cornevin).
The acid oxalates seem especially harmful to _sheep_, causing loss of appetite, exhaustion, small and scarcely perceptible pulse, rapid breathing, and constipation, and in many cases severe diarrhœa, uncertain gait, and sometimes death (Müller).
The milk of affected cows is with difficulty made into butter (Pott).
=Polygonum= sp. Several species of _Polygonum_ are said to have poisonous properties. The chief among them is Buckwheat (_P. Fagopyrum_), the grain of which is widely grown as a food for both man and live stock. This plant, particularly the flowers, has given rise to a well-known rash in man, cattle, sheep, and pigs, with congestion and tumefaction—especially of the head and ears. There is also nervous disturbance, with agitation and hallucination—sheep, for example, may butt against objects. The affection of the nervous centres may lead to fatal results, which have followed in cattle, sheep, and pigs. Little is known of this so-called _Fagopyrism_, but after analytical and spectroscopical researches on the colouring matter of the tegument Kurt concluded that it is due to the chlorophyll.