488 BELLADONNA 



that of the kidneys, by which atropine is quickly excreted 

 unchanged. 



GENERAL ACTIONS. Atropine depresses the functions of 

 sensory nerve-endings, and hence allays irritability and pain 

 when applied to the itching or erythematous skin, when 

 injected subcutaneously into a tender muscle, or into the 

 neighbourhood of an irritated nerve, and also when 

 carried in large doses to internal organs. Moderate or 

 large doses increase heart action, by paralysis of the 

 vagus-endings in the heart, while they raise blood-pressure 

 by stimulating the medullary centre. They powerfully 

 stimulate the respiratory centre. These cardiac and 

 respiratory actions explain the value of atropine in the 

 treatment of collapse, difficult or impaired breathing, and 

 weakness from toxins and other sedative poisons. 



Paralysing the special secretory nerve-endings of glands, 

 atropine is a powerful antisecretory, diminishing or arresting 

 secretion, and exerting this effect in whatever way it is 

 used. Although devoid of action on voluntary muscles, 

 moderate and large doses paralyse involuntary muscles, 

 probably indirectly through the local nervous mechanism, 

 and thus prevent griping and relax spasm of the hollow 

 organs. A similar action on the bronchial muscles prevents 

 spasmodic contraction of the bronchioles in asthma. In 

 almost all animals atropine dilates the pupil, renders the eye 

 bright, dry, and injected, paralyses the power of accommoda- 

 tion, and slightly increases intraocular tension. These 

 effects result alike from the local and internal use of atropine, 

 and depend upon its paralysing the third nerve terminals, 

 and perhaps stimulating the sympathetic. Dilatation of the 

 pupil reaches its maximum in dogs in twenty to twenty-five 

 minutes, in herbivora in thirty-five to forty-five minutes. 

 The effects of full doses of atropine last several days, but 

 those of homatropine, although as quickly produced, pass 

 off more rapidly. 



Full doses cause dryness of the mouth, thirst, difficulty 

 in swallowing, quickened pulse, delirium, with a tendency to 

 irregular movements. The brain centres are stimulated, 

 but the ends of motor nerves are paralysed, and hence result 

 the concurrence of delirium, irregular movements, and 



