283 VEGETABLE DRUGS 



motor nerves controlling them are depressed by toxic amounts of the 

 alkaloid. 



Atropine has been used successfully to produce three diverse actions 

 on the bowel: (1) to quiet intestinal movement in inflammation of the 

 bowels; (2) to relieve spasm in colic and spastic conditions generally; (3) 

 very commonly to aid catharsis by preventing griping. In practice, 

 small doses usually suffice, while, on the other hand, enormous doses (gr. 

 l/l2, instead of the usual dose of gr. l/lOO) have proved successful in 

 moving the bowels in obstinate constipation (in human patients) due to 

 obstruction when all other means failed. It is probable in these cases 

 that the obstruction was due to spasm, or fecal impaction with spasm, and 

 not mechanical. Conversely, it is the common practice to give atropine 

 with morphine to prevent peristalsis in peritonitis and with satisfactory 

 results, owing to the depressing action on the motor nerve (vagus) end- 

 ings in the small intestines overcoming peritoneal irritation. 



The predominant action of belladonna in paralyzing the peripheral 

 vagi in the heart has been described. 



The pneumogastric terminations are depressed in the heart by mod- 

 erate doses, while paralyzed by large quantities of belladonna. 



A like depressing influence is believed to be exerted upon the effer- 

 ent nerve endings of the unstriped muscles of the bladder, urethra, bile 

 ducts, uterus and vagina. Belladonna acts medicinally as an antispas- 

 modic in relation to the muscles. 



Respiration. — Small doses of atropine do not affect the respiration. 

 Large therapeutic doses make the respiratory movements quicker and 

 deeper, by stimulation of the medullary respiratory centre. Fatal doses 

 produce respiratory failure and asphyxia, owing to paralysis of the respi- 

 ratory centre and the peripheral vagus filaments concerned with the res- 

 piratory movements. Belladonna also paralyzes the peripheral fibres of 

 the pneumogastric nerve in the bronchial tubes and acts therapeutically as 

 follows: 1. As a respiratory stimulant. 2. As an antispasmodic, by de- 

 pressing the efferent vagus endings in the bronchial tubes and relaxing 

 spasm of the smooth muscle of their walls. 3. As a sedative, by depress- 

 ing the afferent vagus fibres and diminishing the irritation produced by 

 secretion, so that cough is allayed. 4. As an agent lessening secretion. 



Temperature. — Moderate doses of belladonna cause a rise of tem- 

 perature, while fatal doses lessen bodily heat. The first phenomenon is 

 produced by stimulation of the thermogenic centres, while the latter effect 

 follows the vasomotor paralysis which occurs after lethal doses. 



An elevation of 2 to 5.4° F. has been noted in dogs after full doses 

 of atropine, while a greater fall of temperature has been observed in the 

 same animal in fatal poisoning. Elevation of temperature is accom- 

 panied by increased heat loss, caused by radiation from the dilated 

 cutaneous vessels. 



Eye. — The action of belladonna upon the eye affords another illus- 

 tration of the depressing action of the drug upon the nerve terminations. 

 The myoneural junctions of the third (oculomotor) nerve in the circular 

 muscle are paralyzed, which leaves the radiating fibres free to act and 



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