576 SOLANACEA. 
Amongst the most remarkable and earliest indications of the 
action of belladonna is dilatation of the pupil, and loss of the 
power of accommodation, the degree and. persistence of these 
symptoms being in proportion to the dose employed. The 
defects of vision produced by the drug are various, there may 
be want of defining power, diplopia, presbyopia, want of the 
power of accommodation or even amaurotic amblyopia. Some 
of these defects may even persist when the natural diameter 
ofthe pupil has. been restored by eserine or has gradually 
recovered its normal condition, which indicates that the retina 
itself has lost some of its sensibility. The manner in which the 
drug acts upon the pupil has been much discussed by physiolo- 
gists; Gubler, who has thoroughly investigated this question, 
admits that the various theories which have been suggested, 
viz.—paralysis of the iris, excitation of. its radial fibres, 
paralysis of the ciliary nerves or their spinal centres, contraction 
of the blood vessels of the veins, torpidity of the ophthalmic 
branch of the trigeminal and of the retina—are individually in- 
- sufficient to explain the physiological fact. He considers it to 
be of a complex nature, and that several of the causes above 
mentioned contribute to its production. The solution of the 
problem becomes more difficult when we consider the resistance 
of the iris of birds to the action of the drug. Rossbach and 
Frdélich have observed that in rabbits and frogs the pupil con- 
tracts before dilating. (Gubler, loc. cit.) 
- Belladonna is antagonistic in certain respects to eserine, 
opium, ergotine and pilocarpine, viz., with eserine and ergotine 
as regards its action on the pupil, with pilocarpine as regards. 
rae its action on the secretions of the skin, and with opium as 
egards its action on the brain. Its antagonism to opium is of 
most importance, as numerous cases: are on record in which 
