MOTOR FUNCTIONS OF THE PRO SOMATIC OUTFLOW 67 



situated in the superior cervical ganglion and the connector fibres 

 leave the spinal cord in the uppermost thoracic anterior roots ; 

 adrenalin here produces its characteristic effect. 



There are in the bird's eye well-defined radial striated 

 muscles, which form the dilatator- muscle of the pupil, in addition 

 to the striated muscles which correspond to the unstriped 

 sphincter and ciliary muscles in the mammalian eye. The 

 innervation of these has been investigated by Zeglinski, who 

 states that their motor nerves are not in the cervical sympathetic 

 but run to the muscle direct in the ramus ciliaris, which arises 

 from the first or ophthalmic branch of the trigeminal. When how- 

 ever we consider that the ophthalmic branch of the trigeminal is in 

 all vertebrates a purely sensory nerve, it does not seem likely 

 that these motor fibres belong to it ; it is much more probable 

 that they have come into the ramus ciliaris from some other 

 source. Two possibilities present themselves, either that, as in 

 the mammal, these motor fibres arise from cells in the superior 

 cervical ganglion which is denied by Zeglinski or that they 

 come from cells in the ganglion stellatum, and reach the tri- 

 geminal by way of the ramus vertebralis. It is not absolutely 

 clear whether the striated dilatator muscle of the bird is homo- 

 logous with the same muscle of the mammal. Grunhagen 

 states that a radial pigmented structure, similar to that in 

 the eye of the mammal, is present in the bird's eye in ad- 

 dition to the striated dilatator muscle ; he did not however 

 recognize the muscular character of these radially arranged 

 pigmented cells in the mammal any more than in the bird. 



With the consideration of the motor cells in the ciliary 

 ganglion, I have now completed the survey of all the outflows of 

 connector fibres to motor nerve cells belonging to the involuntary 

 nervous system. 



