POISONOUS PLANTS 239 



or caffeine. The cautious use of the physiological antidotes, 

 eserine against mydriasis and pilocarpine against the 

 drying up of secretions, is advisable. 



Chemical Diagnosis.— Atropine and the allied alkaloids 

 are separated in the search for vegetable poisons in cases of 

 poisoning by any of the plants of this group. A very 

 valuable test is an observation of the mydriatic effect on 

 the eye of a cat. A good chemical test is Vitali's. The 

 residue of alkaloid is heated on the steam bath to dryness, 

 with a few drops of concentrated nitric acid. On moistening 

 the yellow residue with alcoholic potash, atropine and its 

 allies give a red-violet colour. The test is exceedingly 

 delicate. 



. Hyoseyamus. 



Botanical Characters. — Hyoseyamus niger (Pig. 32), or 

 black henbane, is a coarse, erect, branching annual, 1 to 

 2 feet high, more or less hairy and viscid, with a nauseous 

 smell. Leaves rather large, sessile, the upper ones clasping 

 the stem, ovate, and irregularly pinnatifid. Flowers very 

 shortly stalked, ,the lower ones in the forks of the branches, 

 the upper ones sessile, in one-sided leafy cymes, rolled back 

 at the top before flowering. Calyx short when in flower, 

 but persists round the fruit, and then an inch long, strongly 

 veined, with five stiff, broad, almost prickly lobes. Corolla 

 above an inch long, pale, dingy yellow, with purplish 

 veins. Capsule opening transversely, with numerous small 



The henbane is somewhat rare, and of similar habitat to 

 that of the deadly nightshade. In the United States it 

 occurs as a weed of European origin. The West African 

 H.falezlez, according to Cornevin, is eminently poisonous. 



Symptoms. — Henbane poisoning is infrequent, but 

 the plant is sometimes cultivated for medicinal use, and 

 J. R. Welsby* has placed upon record a case in which 

 animals were poisoned in a field thus cultivated several 

 years previously. 



* Vet. Beeord, 1903, p. 181. 



