_Toxic Principle._ The foxglove contains several poisonous glucosides, investigated by Kiliani, Schmiedeberg, Cloette, Bourquelot, Herzig, and others. The following substances are toxic: _Digitalin_ (C_{35}H_{56}O_{14} or C_{36}H_{58}O_{14}) in the seeds and leaves; _Digitonin_ (C_{54}H_{92}O_{28} or C_{55}H_{94}O_{28}) in the seeds; _Digitalein_, only in small quantity; _Digitoxin_ (C_{34}H_{54}O_{11}) in the leaves; and _Digitin_. The toxic property of the foxglove is not lost on drying or boiling. _Symptoms._ Digitalis is an active heart poison, and causes nausea, pressure in the region of the stomach, with diminished pulse, darkening of the field of vision, dizziness, buzzing in the ears, and usually dilated pupils. According to Pammel the symptoms in animals are dullness, lassitude, loss of appetite, nausea, flatulence, diarrhœa; infrequent, full pulse (reduced 6–10 beats in the horse); and contracted pupils. In fatal cases these symptoms are followed by severe colic and tympanites; rapid, feeble, dicrotic, irregular or intermittent pulse (120–140 in horses), while the heart may be heard and felt beating wildly and strongly, and a systolic blowing murmur can frequently be detected. This is due to mitral or tricuspid regurgitation caused by irregular contraction of the columnæ carnæ. The pulse is imperceptible because of the failure of the heart to fill the vessels. The extremities are cold, the eye is protruding, and salivation occurs. Bloody diarrhœa is very often present and the urine may be suppressed. The breathing finally becomes difficult and death ensues within a few hours, or as late as several days. The following account of the symptoms of poisoning in various animals is collected by Lander:— Horses. On the first day sleepiness, swollen eyelids, dilated pupils, injected conjunctivæ, considerable swelling in submaxillary space; respiration normal, temperature 103·5° F.; pulse full, between 65 and 75, very intermittent, being occasionally normal; the second heart sound frequently obliterated. On the next day laboured breathing, head immensely swollen, tongue greatly enlarged and protruding, pulse 80 and most erratic, temperature very slightly up, great restlessness. Respiration became more difficult and stertorous, tongue and buccal membranes livid, jugular standing out. A mare experimentally poisoned showed on the _third day_ dullness and loss of appetite; _fourth day_ nauseated; nose, mouth, and ears cold; abdomen blown, with colicky pain, and occasional pawing; pupil somewhat contracted, pulse firm at axilla and heart, but not perceptible at jaw; at 4.30 p.m. she was down, much pained, and attempting to roll; pulse 82, but unequal; _fifth day_, pulse, imperceptible at jaw, about 120; respiration 25, and very much laboured: lips retracted and saliva dripping from the mouth; enormous abdominal tympanites, and much pain; rapid sinking: died _sixth day_.