104 
PHYSIOLOGICAL ACTION OF ATROPINE. 
eye occurred to such an extent, that scarcely more than the 
border of the iris remained visible, while the pupil of the eye 
on the side where the sympathetic was divided, became 
dilated only to about one-half \ and remained in that condition 
during several hours. As the result of the first experiment 
negatives the idea of atropine exciting the nerve filaments 
supplying the radiating fibres through which the dilatation of 
the pupil is produced, we are forced to the conclusion that, in 
the present case, the semi-dilatation must originate, or rather 
depend upon, paralysis of the nerve supplying the circular 
fibres which govern the contraction of the pupil. We shall 
see, in the sequel, in how far the phenomena observed in 
another experiment tend to confirm this view. 
'Experiment 3 . — The conjunctiva of the right eye of a dog 
was moistened with a single drop of the solution of atropine — 
in half an hour the adjacent pupil became fully dilated, while 
the iris of the opposite eye was not observed to be in the 
least degree affected. 
Experiment 4. — On another occasion, several drops of the 
same solution were at different times brought in contact with 
the eonjuntiva of one of the eyes; and not only did the 
adjacent pupil, but also that of the other eye, become fully 
dilated. 
The results of these last three experiments induce me to 
coincide with the theory advanced by Mr. Benjamin Bell. 
According to his view, the atropine must have, in all three 
instances, passed into the circulation before making its pre- 
sence known by its characteristic action upon the pupil. 
That in the local application in Experiment 3, the quantity 
of the alkaloid employed, although extremely minute, was 
nevertheless able to reach the periphery of the nerves of the 
iris so speedily, as to be still sufficiently concentrated to pro- 
duce dilatation of the pupil ; but that, by the time it arrived 
at the heart, and became diffused through the general mass 
of the blood, it was too much weakened by dilution to be 
capable of acting either on the root, in the course, or at the 
periphery of the nerve supplying the opposite eye with suffi- 
cient power to cause dilatation of the pupil. On the other 
hand, in Experiments 2 and 4, the quantity of atropine (in 
the one case absorbed by the capillaries of the muscles of the 
neck, in the other by those of the conjunctiva and adjoining 
tissues) was sufficiently great, that, notwithstanding its being 
first diffused through the general circulation, it arrived at the 
