PLANTS SUSPECTED OF BEING POISONOUS.
A very large number of plants have at various times been suspected of
possessing poisonous properties and causing harm to live stock. Of these
it is quite probable that many are in practice entirely harmless, but
some must be included as possibly deleterious, complaints having been
made which vary in gravity from a slight irritation to causing death.
=Purging Flax= (_Linum catharticum_ L.). It is perhaps doubtful whether
this plant is really poisonous unless taken in considerable quantity by
animals—as it is quite unlikely to be. It may, however, be included
here, as it is stated to contain a glucoside which is purgative and
which on fermentation yields prussic acid.
=Furze= or =Gorse= (_Ulex europæus_ L.). In view of the fact that
Gerrard isolated from the seeds of Gorse the alkaloid _Ulexine_, which
is identical with _Cytisine_ (p. 27) and that the alkaloid is also
contained in less quantity in the bark of young shoots, this plant has
been suspected of possessing toxic properties. Experiments (179)[7] with
the alkaloid definitely showed it to be a nerve and muscle poison, 3
milligrammes having killed a chloroformed cat with convulsions in three
minutes, though the animal could be kept alive as long as artificial
respiration was kept up. As, however, Gorse has long been used very
widely and in considerable quantities as a fodder the percentage content
of the alkaloid must in general be exceedingly small, and no harmful
effects need be feared from the consumption of the cut and bruised
plant. Possibly the seeds might prove injurious if eaten in quantity.
Footnote 7:
Reference to Bibliography.
=Melilot= (_Melilotus_ sp.) may at times cause injury. Ewart (82)
writes: “All the species contain Cumarin, a volatile odoriferous
principle, which in excess produces a disinclination to locomotion,
paralysis and ultimately fatal symptoms. No harm is to be apprehended if
the amount present does not exceed 10 per cent. of the herbage.”
=Silver Weed= (_Potentilla Anserina_ L.). This well-known and elegant
little weed is scarcely likely to be eaten to any extent by farm stock,
though it may possibly be taken occasionally on roadsides. It has not
been proved to be poisonous, but Pott states that it has a strongly
constipating effect (213).
=Tormentil= (_Potentilla Tormentilla_ L.). In relation to supposed
bracken poisoning (see p. 87) in regard to which experiments were
conducted by the Board of Agriculture and Fisheries, Tormentil occurred
in several instances with the bracken in localities where this plant was
reported to cause poisoning. Two feeding experiments in which the weed
was fed to heifers gave negative results. In a further case, however, 4
or 5 lb. were collected from a field where sick animals were grazing,
and fed to a heifer; it appeared to be the cause of rise of temperature
(to 106° F.), diarrhœa, and the passing of a considerable quantity of
blood in the fæces for three days, after which the animal improved. It
was, however, slaughtered, and lesions were found similar to those found
in animals dying in the field from so-called bracken poisoning. Though
the plant was suspected, results generally were not held to prove that
it was the cause of poisoning (25). According to Van Rijn the root of
Tormentil contains a considerable quantity of _Chinovic acid_
(C_{32}H_{48}O_{6}?).
=Wall-Pepper= (_Sedum acre_ L.) is regarded as emetic and purgative, but
to lose the harmful properties on drying.
=Sundews= (_Drosera_ sp.) are reputed to be poisonous to sheep, but no
evidence has been found.
=White-Rot= or =Marsh Penny-Wort= (_Hydrocotyle vulgaris_ L.) is stated
to have caused inflammation of the digestive tract, and hæmaturia; and
to contain a toxic substance _Vellarin_ (213).
=Wild Parsnip= (_Pastinaca sativa_ L.). This plant has often been
supposed to be poisonous, but Pammel shows that in Iowa the plant is
quite harmless, as it appears to be in Britain.
=Devil’s-Bit= (_Scabiosa succisa_ L.) is stated by Moir to have caused
injury to cattle in one instance (_Vet. Record_, 1899), causing
salivation, gritting of the teeth, twitching of facial muscles, and
slightly protruded, abraded, swollen and sensitive tongue. An experiment
on cattle showed the plant to induce violent inflammation of the mouth
and tongue.
=All-Heal= (_Valeriana officinalis_ L.) is not likely to be eaten by
stock in sufficient quantity to cause poisonous symptoms, though it is
stated to contain the poisonous _Valerianic acid_ and _Oil of Valerian_.
According to Chevalier (_vide_ Henry) this plant contains an alkaloid
not yet fully characterised.
=Canadian Erigeron= (_Erigeron canadensis_ L.), sporadic in England, is
suspected in America. It contains an oil, chiefly a _terpene_
(C_{10}H_{16}). It has an acrid taste, causes smarting of the eyes,
soreness of throat, aching of extremities, and colic; and irritation to
people handling it (203).
=Mayweeds= (_Anthemis_ sp.). It is not at all clear whether these plants
are more than irritant in character, and they are so very common and
widely distributed that there would probably be more evidence if they
were poisonous. _A. Cotula_ is regarded as suspected by Smith and
Halsted, while Ewart says that it is obnoxious to stock on account of
its unpleasant flavour, and if eaten by them in time of scarcity is apt
to give their flesh, milk, or butter an unpleasant flavour. Güssow
states that this species blisters the mouth and nostrils of animals. In
his investigations at Kew, Greshoff found that the seeds of _A. Cotula_
and _A. arvensis_ contain much hydrocyanic acid. (He further found that
the cyanogenetic glucoside from _A. aetnensis_ Schouw. and _A. chia_ L.
belongs to the amygdalin type, giving off hydrocyanic acid and
benzaldehyde on hydrolysis. “The strong odour of benzaldehyde may even
be observed on grinding the seeds with water. Species of _Anthemis_
contained from 0·15 down to 0·03 per cent. of hydrocyanic acid.”)
=Cat’s-Ear= (_Hypochæris radicata_ L.). No record of poisoning of Cat’s
Ear has been found, but it may be mentioned here, since Ewart says of
it: “It contains a bitter, milky sap, which makes it unpalatable though
not entirely poisonous.... An exclusive diet of this weed could not help
but injure stock eventually.”
=Dodders= (_Cuscuta_ sp.), when parasitic on clovers and fed as fodder
or hay, have been suspected of causing digestive troubles in horses and
cattle in the United States. Müller records a case of poisoning of young
pigs by _C. europæa_, with inflammation of the intestines and nervous
symptoms. Barbey determined the presence of the glucoside _Cuscutin_ in
_C. Epithymum_.
=Viper’s Bugloss= (_Echium vulgare_ L.) is suspected of being poisonous;
according to Friedberger and Fröhner it causes slavering (see also
_Cynoglossum_).
=Hound’s Tongue= (_Cynoglossum officinale_ L.). To what extent this
plant is actually poisonous is not clear, but with some other members of
the order (_Echium vulgare_, _Anchusa officinalis_), it contains the two
alkaloids _Consolidine_ and _Cynoglossine_—the former of which paralyses
the central nervous system and the latter the peripheral nerves.
(Greimer, 1900: _vide_ Henry).
According to Hooker, Hound’s Tongue is narcotic and astringent, and
Smith includes it as a simple vegetable irritant, causing nausea and
purging. No records of actual poisoning of animals have been found.
=Broom-rape= (_Orobanche minor_ Sutt.) has been suspected, and according
to Boitel is liable to cause violent colic when it occurs in
considerable proportion in clover and is ingested with it (73). On the
other hand, in a case noted by Stapledon, in which Broom-rape (_O.
minor_) had completely overrun the aftermath on a farm near Fishguard,
two-year-old cattle devoured the plant with apparent relish and cleared
off most of it in a few days after being turned in. The farmer stated
that he saw no trace of colic or other ill effects. (_Jour. Bd. Agric._,
September, 1916.)
=Great Mullein= (_Verbascum Thapsus_ L.). Though it does not appear to
be touched by farm live-stock the Great Mullein must be mentioned here.
The leaves and flowers have been used medicinally as an emollient and
pectoral, while the seeds possess narcotic properties and serve to
stupefy fish (73). Pammel states that the plant causes irritation, but
is probably not very poisonous to stock.
=Toadflax= (_Linaria vulgaris_ Mill.). Cornevin describes Toadflax as
acrid and poisonous, but says that stock reject it, and he could record
no accidents to animals. In his full and excellent account of this weed,
Kraus says it is regarded as poisonous, or suspected of being so, but
that according to most accounts it is not harmful to cattle (168).
Leunis regards it as suspicious on account of its acridity. Some German
authorities say it is willingly eaten by cattle, but it is generally
believed to be avoided, and owing to its disagreeable odour and acrid
taste this view is probably correct. The plant has not been exhaustively
studied, and while Smith gives the toxic principle as _Oil of
Snapdragon_ and the resin _Gratiolin_, it may be observed that Toadflax
contains the glucoside _Linarin_ (C_{64}H_{56}O_{40}).
=Figworts= (_Scrophularia nodosa_ L. and _S. aquatica_ L.). These plants
are not likely to be eaten by animals, but Cornevin states that the
former is strongly emetic and purgative, and that in excess it may cause
superpurgation ending in death. Müller says that the two species have
respectively caused poisonous symptoms in a cow and a sheep; in the case
of the cow there were loss of appetite and symptoms of paralysis. From
_S. nodosa_ Walz extracted a bitter, crystalline substance,
_Scrophularine_.
=Yellow Rattle= (_Rhinanthus Crista-galli_ L.). When grass land is put
under the plough Yellow Rattle present may re-appear in a cereal crop as
a semi-parasite, and its seeds may later be ground up with the grain,
imparting a reddish or violet-brown colour and an unpleasant taste to
the flour and even bread made from it. It is strongly suspected of being
poisonous, like _Pedicularis_ and _Melampyrum_, but it is by no means
clear how far it may prove harmful to stock. It is believed by some
people to impart a bad taste to the butter made from the milk of cows
grazing on infested pastures. Lehmann ate without harm 35 grammes (about
1¼ oz.) of the seeds made into a cake and cooked; and during four days
he gave a rabbit 1238 grammes (2·7 lb.) of the fresh plant with
half-ripe seeds, without apparent injury (73).
In some poor pastures it occurs in excessive quantity, and would appear
to be only very slightly poisonous, or would have attracted wider
attention. It is possibly only poisonous after being eaten for a
prolonged period, as in the case of _Lolium temulentum_, and _Lathyrus
sativus_. The seeds contain the bitter-sweet glucoside _Rhinanthin_
(C_{29}H_{52}O_{20}), which is suspected of having poisonous properties.
=Cow-Wheat= (_Melampyrum arvense_ L.). It seems clear that Cow-Wheat is
at least not poisonous unless eaten in very considerable
quantities—amounts in fact which in practice are most unlikely to be
eaten. The seeds may occur in cereal grains, and hence be ground up into
meal. As they are said to contain a glucoside analogous to _Rhinanthin_,
have a bitter taste and peculiar odour, and impart a violet coloration
to flour, their presence in cornfields is most undesirable. According to
Pammel this plant induces sleepiness and colic.
=Ground Ivy= (_Nepeta Glechoma_ Benth.) is, according to Schaffner,
poisonous to horses. It contains a volatile oil and bitter principle, as
also does Catmint (_N. Cataria_). In a case which came before the Board
of Agriculture and Fisheries in 1906 three horses became ill with
symptoms of poisoning, and the only weed found in the lucerne they were
getting was Ground Ivy, and this was suspected but not proved to be the
cause. In a further case, reported in 1909, eleven horses were believed
to have been poisoned by this weed, and in one of the dead horses
scarcely any food but Ground Ivy was found, and to it the veterinary
surgeon in attendance attributed death. During preceding years several
horses had died in the locality (Ely), owing, it was believed, to
poisoning by the same weed. The losses, however, were not _proved_ to be
due to this plant.
In the _Veterinary Journal_ (October, 1914, p. 515) poisoning of horses
by this weed was noted (after Ferenczhazsy in the _Recueil de Médecine
Vétérinaire_). The author observed nine cases of intoxication due to the
weed, though it is stated that it “has occasioned no trouble in cattle
and sheep that consumed it.” The symptoms in horses were “anxious look,
dyspnœa, salivation, sweating, dilatation of the pupils, cyanosis, signs
of pulmonary œdema.” Two horses died. In 1913 similar cases were
observed by other owners, and terminated fatally.
Hooker states that _N. Glechoma_ is “bitter and aromatic, formerly used
for beer, occasionally for tea.”
=Orache= (_Atriplex_ sp.). So far as known these plants are not
poisonous, but it may be stated that Greshoff found the seeds of five
species, and the leaves of two species, to contain a _Saponin_.
=Nettles= (_Urtica_ sp.). Nettles are not generally regarded as
poisonous otherwise than as causing painful nettle rash on the bare
skin, but _Urtica dioica_ L. is stated to have caused the death of dogs
(_Berliner Tierärztliche Wochenschrift_, 1909).
=Yellow Flag= (_Iris Pseud-acorus_ L.). The wild Flag was noted by
Linnæus as dangerous to cattle, but no case of actual poisoning has been
found in the literature. The plant is stated to have marked emetic and
purgative properties, and Cornevin remarks that in Belgium intense
gastro-enteritis is attributed to it. It contains the glucoside _Iridin_
(C_{24}H_{26}O_{13}).
=Narcissus= sp. Various Narcissi (_e.g._ _N. pseudo-narcissus_, _N.
poeticus_, and others) have been regarded as irritant to the hands.
They would rarely if ever be eaten by live-stock in Britain, but it
is stated that on the Continent many poisonings of cattle, goats,
and pigs have been recorded, not infrequently ending in death after
two or three days. The Narcissi are strongly narcotic, emetic, and
purgative, and cause dilated pupils. Pott states that they cause
inflammation of the digestive tract, and convulsions, sometimes with
fatal results; and according to Pammel _N. poeticus_ induces intense
gastro-enteritis. _N. pseudo-narcissus_ contains the alkaloid
_Narcissine_ (C_{16}H_{17}O_{4}N), which with cats causes nausea and
purgation (Henry).
=Common Fritillary= (_Fritillaria Meleagris_ L.). The Fritillary or
Snake’s Head occurs only in a few places in England, and truly wild
perhaps only rarely in southern and eastern counties—not in Scotland or
Ireland. No definite case of poisoning has been found in the literature,
but the plant is stated to be poisonous. It contains the bitter alkaloid
_Imperialine_ (C_{35}H_{60}NO_{4}), which is a heart poison.
=Bog Asphodel= (_Narthecium ossifragum_ Huds.) has by some been regarded
as a poisonous plant, and Müller says that the poisoning of cows has
been recorded, and also that a cat died after drinking the milk of an
affected cow. The toxic property is believed to be the glucoside
_Narthecin_.
=Molinia caerulea=, _Moench_. A short account by Pott shows that when
forming the principal part of moorland pasture grasses, and hence
extensively eaten, this grass causes brittleness of the bones of stock,
and in sheep chlorosis and wool eating. It also induces hæmaturia, but
if free from parasitic fungi (_e.g._ _Claviceps microcephala_) and not
covered with microscopic, sharp crystals, is quite harmless if only
eaten as a secondary or incidental fodder. This grass seems to be very
poor in lime (Immendorf, 1898), and Schulze and Castoro found the
internodes of the stem to contain a considerable quantity of a pentosan
(Xylan). It is poor in nutritive constituents. The harm done is due
perhaps in part to this fact, and in part to more or less accidental or
occasional constituents (as 0·046 per cent. of lead oxide in a case of
the var. _altissima_ near some lead works). Plants said to be
occasionally similarly harmful are _Juncus_ sp., _Nepeta Glechoma_, and
_Hieracium Pilosella_.