BELLADONNA. 303 



slowing action on the cardiac centre in the medulla, already 

 seen ; but they are quickly paralysed, the pulse rising in fre- 

 quency to twice its previous rate after full doses ; and this 

 frequency cannot he reduced hy faradising the vagus. There- 

 with the force of the systole is not reduced after moderate doses. 

 Very large (poisonous) doses depress the ganglia, and finally 

 even the muscle, and death occurs through cardiac failure, with 

 the ventricle in diastole. The depressor and the accelerator 

 filaments are not affected. 



It will be convenient to complete here the account of the 

 action of belladonna on the circulation. The vaso-motor stimu- 

 lation noted under the medulla, coincides with the cardiac 

 acceleration, and thus the blood pressure is decidedly raised, 

 the heart emptying itself more frequently into tense vessels. 

 Large doses, however, depress the vaso-motor centre ; the peri- 

 pheral vessels relax ; the pressure falls ; and if this be 

 extreme, it coincides with the paralysis of the cardiac ganglia 

 and muscle, and contributes to the final arrest of the cir- 

 culation. 



The terminations of the vagus in the bronchial walls are 

 paralysed by atropia, the tension of the muscular coat of the 

 bronchi diminished, and the air current thus facilitated. The 

 afferent branches of the vagus in the same parts are also 

 paralysed, thus diminishing sensibility and reflex action, that 

 is, dyspnoea and cough. These effects are in addition to the 

 stimulation of the respiratory centre already noticed. 



The inhibitory branches of the splancnnics in the intes- 

 tinal walls are depressed by atropia, which thus increases the 

 peristaltic movements, and causes relaxation of the bowels. 

 It is doubtful whether the ganglia and plexuses, and the 

 muscular coat, are also affected. The vaso-motor fibres of the 

 splanchnics, however, resist atropia. 



Atropia appears to affect the terminations of the nerves of 

 the urethra, bladder, and vesiculce seminales, but this part of its 

 action is still obscure. Frequent desire and inability to pass 

 water is a symptom of overdoses. 



Metabolism and temperature. Nutritive activity is increased 

 by belladonna, obviously through the increased circulation and 

 respiration ; and most of the solid excretions are increased, as 

 will be seen under the urine. The temperature is corre- 

 spondingly raised ; but sinks with the failure of the circulation 

 after large doses. 



4. SPECIFIC USES. 



From its sedative effect on the convolutions, belladonna 

 in full doses has been given in the low delirium of fevers, 



