ATROPINE 489 



lassitude. Like alcohol, atropine exerts primary stimulant 

 and secondary paralysant action. It stimulates, then 

 depresses the respiratory centre, and death results chiefly 

 from paralysis of respiration. Small doses stimulate, but 

 large paralyse the motor areas of the brain and the centres 

 of the medulla. The vaso-motor medullary centres, as well 

 as the peripheral vaso-motor ganglia, are stimulated by 

 small, but paralysed by large doses. Small doses conse- 

 quently raise blood-pressure and temperature. Continued 

 use does not confer any tolerance as occurs with opium or 

 arsenic. 



Belladonna resembles hyoscyamus and stramonium, but 

 is more active. It is somewhat similar to opium in its 

 antispasmodic and anodyne effects ; but the distinctions 

 between the two are marked and various. Fairly large 

 doses of belladonna or atropine stimulate and subsequently 

 paralyse the central nervous system, and produce delirium, 

 restlessness, and continued movements, followed by depres- 

 sion and coma ; while similar doses of opium or morphine 

 paralyse more particularly the brain centres causing narcosis 

 and coma. Belladonna paralyses the vagus-endings and 

 inhibitory mechanism of the heart, and hence accelerates 

 the pulse, while opium slows it by central action. Atropine 

 stimulates, while morphine depresses the respiratory centre. 

 Atropine dilates, morphine contracts the pupil. The second- 

 ary effects of belladonna ally it to hemlock, which it also 

 resembles in dilating the pupil, and paralysing the ends 

 of sensory nerves. Atropine has no direct physiological 

 antagonist, but morphine, caffeine, Calabar bean, prussic 

 acid, and especially pilocarpine oppose some of its actions. 

 Methyl and ethyl atropine, although paralysing the ends 

 of motor nerves and retaining the specific effects of atropine 

 on the eye, heart, and respiratory centre, have no tendency 

 to tetanise. 



Toxic EFFECTS. Horses were subjected to experiment by 

 Hertwig. Twenty received four to six ounces of the dry 

 pulverised herb, with meal and water, in four separate 

 doses, at intervals varying from four to eight hours. In 

 four or five hours, and on the succeeding day, he observed 

 dulness, languor, uneasiness, dilated pupils, and a feverish 



