190 = in 30 seconds. 



4 



;> 





10 



» 





10 



j> 



30 



12 



» 



30 



13 



>j 



30 



774 DR FRASER ON THE PHYSIOLOGICAL ACTION 



The examination of the cervical sympathetics was resumed soon after the poison was exhibited, 

 with the following results : — 



In 2 min. after the administration, stimulation of the ") 



left sympathetic with the secondary coil at J 



do. do. 185 = dilatationfrom7tol5inl0sec. 



do. do. 188 = in 30 seconds, 



do. do. 185 = dilatationfrom5toloinl0sec. 



after the administration, left pupil = 4, right pupil = 5. 



do. stimulation of the ) 1 r>r_ ( - ) • qa -, 



left sympathetic with the secondary coil at j 

 14 „ „ after the administration, stimulation of the \ -.n r _A 

 right sympathetic with the secondary coil at j 



14 „ 35 „ after the administration, stimulation of the "1 - I( ?a_ ( - ) 



left sympathetic with the secondary coil at J 



15 „ 30 „ do. do. 90 = 



The rabbit was now dead, and both pupils had been for more than two minutes previously 

 in a state of extreme contraction. 



In 16 min. 10 sec. after the administration, stimulation of the "I oa _ a • oa j 



right sympathetic with the secondary coil at J 



17 „ „ after the administration, stimulation of the "I -i a _ a 



left sympathetic with the secondary coil at J 



18 „ „ after the administration, stimulation of the ) -i a _ a 



right sympathetic with the secondary coil at j 

 The left iris was at this time exposed by cutting away a portion of the cornea. The elec- 

 trodes were applied directly to its surface, near the external margin, when a slight and rapid 

 contraction of the iris (dilatation of the pupil) occurred, instantly followed by a rebound to its 

 previous condition. This effect was frequently produced during many minutes after death, but 

 no distinct expansion of the iris (contraction of the pupil) could be caused when the electrodes 

 were applied in the same way to the pupillary margin. It must, however, be added that the 

 pupil was at this time in a very contracted condition. 



We learn from this experiment that the cervical sympathetic is paralysed before 

 the death of the animal, while a portion of the apparatus that is immediately 

 concerned in the contraction of the iris retains its vitality for a considerable period 

 afterwards. The cause of the pupillary contraction during poisoning by internal 

 administration is, therefore, in all probability, to be found among those con- 

 sequences that naturally succeed the removal of the influence of the cervical 

 sympathetic nerve. Without dogmatising on this subject, and feeling content 

 in the meantime with the mere narration of these facts, I am inclined to think that 

 such changes of the iris can only be explained by considering the influences of dila- 

 tor and constrictor muscles, and also of a system of contractile blood-vessels. 



An animal struggles violently during the action of a poison, and the pupil 

 dilates. It is natural to suppose that, in this case, the excited spinal nerves had 

 produced increased action of the dilator muscle, and that thereby the antagonism 

 of the constrictor had been overcome. But if iridal movements are merely the 

 results of spinal or cerebral nerve-force interfering with antagonism between 

 muscles, how account for the continuation of either dilatation or contraction after 



