302 MATER i A MEDIC A AND THERAPEUTICS. 



become more frequent and more deep. This effect is indepen- 

 dent of the blood pressure. Poisonous doses paralyse the same 

 centre. The cardiac centre is for a time stimulated and the 

 heart slowed. This is but a small part of the effect on the 

 heart, as will be immediately seen. The vase-motor centre 

 is first stimulated and then depressed by belladonna : that is, 

 the systemic arteries are contracted and the blood pressure 

 raised for a time; afterwards the vessels relaxed, and the 

 pressure lowered, causing the flushing of the skin. The irri- 

 tability of the motor nerves is diminished, but not lost, except 

 after large doses. The voluntary muscles remain unaffected. 

 The sensory nerves, which, as we have seen, are locally depressed, 

 are also depressed specifically. Thus pain is prevented or 

 relieved. 



Special efferent nerve terminations. A markedly depressing 

 action is exerted by belladonna upon the terminations of cer- 

 tain special motor or secretory nerves in connection with the 

 viscera, or upon the " terminal apparatus" between these fibrils 

 and the active protoplasm. 



The endings of the third nerve are paralysed in the 

 sphincter of the pupil and in the ciliary muscle, giving rise 

 to the dilatation of the pupil and the disturbance of accom- 

 modation. The effect on the pupil is purely local in its cause ; 

 the muscle itself is also unaffected ; possibly the sympathetic is 

 somewhat stimulated. The amount of confusion of vision 

 produced by the paralysis of accommodation will depend on the 

 normal refraction of the patient's eye, long-sighted persons 

 suffering most. The intra-ocular pressure is not diminished, as 

 is often stated ; it is increased by large doses. 



The terminations of the chorda tympani in the submaxil- 

 lary gland are paralysed by atropia, the result being arrest of 

 saliva, and the dryness of the mouth and throat already men- 

 tioned. The sympathetic remains unaffected, so that the 

 vessels in the gland dilate as usual under stimulation, and the 

 " sympathetic secretion " can be obtained as before. Probably 

 the mucous glands of the mouth are paralysed by atropia at the 

 same time. 



The ends of the sudoriparous nerves in the sweat glands 

 are depressed by atropia, which is the most powerful of all 

 anhidrotics. Therewith the skin is flushed, as we saw over- 

 spread sometimes by a scarlatinoid redness or rash; and the 

 temperature rises at first, but afterwards falls. 



The lacteal nerve terminations are paralysed, and the 

 secretion of milk (if present) arrested. 



The ends of the vagus (inhibitory apparatus) in the heart 

 may be briefly stimulated by atropia, thus increasing its 



