Equisetum arvense.—The field horsetail was reported from Connecticut in 1871 as being poisonous to horses. Cases are very rare, and it is probable that this plant is deleterious only when eaten in considerable quantity, and then perhaps only on account of its physical character. Experiments made in Europe show that a similar species (E. palustre) is fatal to horses when fed in considerable quantity with hay.
TAXACEÆ (YEW FAMILY).
Taxus minor.—The common yew, or ground hemlock, is called poison hemlock in some places. The leaves of this shrub are probably poisonous to stock, as are those of the European yew. This species is more accessible to stock than the western yew (Taxus brevifolia), which grows only in deep cañons.
YEW POISONING (TAXUS BACCATA).
The leaves of yew, when eaten in any considerable quantity, are very poisonous. Two ounces to eight ounces, according to the size of the animal, slow the heart’s action, produce weakness, staggering, and apoplectic congestion, which may have a fatal result in less than an hour. The bark is less injurious, and the fruit is scarcely poisonous at all.
The early symptoms, which are only seen in chronic cases, consist in excitement, followed by somnolence and muscular weakness, with slowing of the respiration and circulation.
POACEÆ (GRASS FAMILY).
Lolium temulentum.—The seed of the darnel, or poison rye grass, an introduced annual especially abundant on the Pacific Slope, is considered poisonous to both man and animals.
Stipa robusta.—This is a perennial plant which is known in Arizona and New Mexico as sleepy grass. It produces a narcotic effect on horses and cattle that feed upon it, but stock bred in that region rarely touch it.
Zea mays.—The numerous deaths that are frequently attributed to Indian corn are mostly due, not to any poison inherent in the plant, but rather to parasitic or saprophytic fungus growths, as noted under Aspergillus and Ustilago. The green fodder is very apt to cause severe and even fatal tympanites if the animal’s diet is not properly regulated. Death has also been attributed to the presence of nitre (potassium nitrate) in the growing stalks. It is supposed that in very rich soil this substance will sometimes accumulate in the stalks in considerable quantity during prolonged drought.