MOVEMENTS OF THE IBIS. 103 



This does not occur when the sympathetic in the neck has 

 been divided. In addition to the inferior cilio-spinal centre, 

 there is a superior centre, which is in communication with the 

 superior cervical ganglion and is situated near the sublingual 

 nerve. The influence of this centre over the pupil cannot be 

 demonstrated by direct stimulation, because it is too near the 

 origin of the fifth, irritation of which has an influence over 

 the iris ; but it is shown by division of its filaments of com- 

 munication with the iris. 1 



Section and galvanization of the different nerves which 

 regulate the movements of the iris have a certain influence 

 upon its vascularity ; and, indeed, it has been thought that 

 contraction is in a measure due to congestion of its vessels, and 

 dilatation, to an opposite condition. This view is adopted by 

 Borne of those who deny the existence of the radiating mus- 

 cular fibres. Assuming that the size of the pupil is, to a cer- 

 tain extent, affected by the condition of the vessels, it is evi- 

 dent that the extensive movements of the iris are due mainly 

 to muscular action. It has been also shown by Brown-Se- 

 quard, that the changes in the iris produced by injection of 

 its vessels are not to be compared with its physiological 

 movements. 3 The changes in vascularity produced by divid- 

 ing or galvanizing the sympathetic do not differ from the 



sixth, and even sometimes as low down as the ninth or tenth dorsal vertebra, 

 affects the iris like the section of the sympathetic, though in a less degree." 

 (Physiology and Pathology of the Central Nervous System, Philadelphia, 1860, 

 p. 144.) 



1 BUDGE, Lehrbuch der speciellen Physiologic des Menschen, Leipzig, 1862, S. 

 767, et seq. 



According to the observations of Chauveau, the cilio-spinal centre acts on 

 the iris as a reflex centre and not as a centre exerting a direct influence. He 

 has shown that excitation of the sensitive roots coming from this region produces 

 the same phenomena as irritation of the posterior columns of the cord, though 

 with less intensity. (CHAUVEAU, Action de la moelle epinere sur Viris. Journal 

 de la physiologic, Paris, 1861, tome iv., p. 383.) 



2 BROWN-SEQUARD, Recherches experimentales sur ^influence excitatrice de la lu- 

 miere, du froid et de la chaleur sur Viris. Journal de la physiologic, Paris, 1859, 

 tome ii., p. 452. 



