According to the current opinion, in man and manijnals, in wjiicli 

 the relations between the nerves and 'th'e raiiscle-ceiis of the. iris are 

 studied profoundly, the sphincter pupiHae is innervated by means of 

 the ganglion ciiiare and the third nerve, the dilatator pupillae how- 

 ever gets its nervous supply from the sympathetic nerve, by means 

 of the superiorcervical ganglion, the ganglion ciiiare and the nervi 

 ciliares longi. Stimulation of the nervus oculomotorius causes the 

 pupil to contract, stimulation of the cervical sympathetic causes the 

 pupil to enlarge. The real innervation of the membrane of Bkich 

 is not known. Only Retzils (1893) asserts to have seen in albinotic 

 rabbits very delicate non-medullaled nerve-fibres running towards 

 the fibres or cells of this membrane and ending in very small knobs 

 lying against the surface of the membrane. In birds, where the 

 structure of the iris-muscles and the function of the sphincter and 

 dilalata pupillae have been studied very profoundly of late years, 

 there is no unanimity of opinion about the relations between efferent 

 nerves and the different muscular systems. Geberg and Melkicü 

 are of opinion that both the circular and the radiating muscle- 

 fibres of the iris are iiinervateil by medullated ner\e-fibres coming 

 from the same source. About the innervation of the membrane of 

 Bruch in the bird's eye we know nothing extxctly. 



Cross sections and especially longitudinal (frontal) sections through 

 well-impregnated preparations of the iris of fowls and pigeons stained 

 after the method of Bielschowsky and treated afterwards with 

 chloride of gold, haematoxylin and eosin showed the following facts. 



In the iris-stroma we find the bundles and plexus of nerve-fibres, 

 containing medullated and non-meduUated fibers, as they were described 

 by Geberg and others. 



The thick medullated nerve-fibres running between the muscular 

 elements of the sphincter pupillae supply them with terminations, 

 which may be compared with the motor nerve-endings (end-plates 

 of Kuenen) of the voluntary muscle-fibres. 



On the muscle-fibres both of the musculus ciliaris and of the 

 sphincter pupillae these efferent nerve-terminations are loose, provided 

 with only a few branches and small endrings or delicate endnets. 

 The motor nerve-fibre usually enters the muscle-fibre at one of the 

 sarcoplasmatic protuberances described above (fig. 9 and 10) and in 

 transverse sections through the muscle-fibres the hyfiolemmal position 

 of these nerve-endings is clearly to be seen (fig. 1 and 5). Undei' a 

 very high power even in these muscles tiie existence of a periter- 

 minal network in the sarcoplasm and the intimate connections 

 between this periterrainal network and the nerve-termination on one 



