478 THE NERVE DISTRIBUTION IN THE EYE OF PECTEN IRRADIANS. 



opinion the posterior wall consists of a homogeneous vitreous humor and a pigment 

 layer with its constituent layers of argentea, while the anterior wall is made up of 

 rods, bipolar and supporting cells, and external ganglionic and supporting cells. 

 Sufficient has been said regarding the comparisons of the elements of the posterior 

 wall. In reference to the anterior wall let us begin the comparison with the rods. 

 The rods have been described by Patten and others as cuticular secretions of the 

 retinophorse, of columnar form and penetrated by the axial nerve-fibre of the reti- 

 nophora. The nerve-fibre passes out at the end of the rod to divide into two branches, 

 one joining with a neighboring fibre the other encircles the rod. From the axial fibre, 

 moreover, radiating branches are given off and these constitute the greater part of 

 the rod substance. Some of these fibres penetrate the sheath to connect with the 

 encircling fibres on the surface, while others join branches from the external ganglionic 

 layer. Patten also described the core of the rod as filled with granules produced 

 by the coagulation of fibrillse. His complex description of the arrangement of the 

 three series of nerve-fibres innervating the rods has been justly criticised, judging 

 from the metltylen-blue preparations. It will be seen from my description that the 

 axial rod-fibre is the axon of a rod-cell and not a continuation of the axial fibre of a 

 retinophora; that it does not branch inside the rod nor penetrate it to divide into 

 two branches, but terminates in the end of the rod. The striae that Patten regarded 

 as coagulated fibrillse in the rod, I consider stainable nerve substance like that which 

 is also seen in the bipolar cells and parallel with their length. The striae are, 'as a rule, 

 not in the form of continuous fibrils or varicose threads. They are abundant in bipolar 

 and rod-cells in which the axon has been broken up during the preparation of the 

 material, and are not fibrillar. The surfaces of the rods are not covered with two sys- 

 tems of nerve-fibres, derived from the axial branches and the external ganglionic. layer. 

 I was able to see that only the finest beaded fibrillse that characterize the branches 

 of the external ganglionic layer terminate on the rod-cells. These on the outside of 

 the rod and the axon in the inside constitute, I believe, the only nerve-fibres of the 

 rod-cells. Patten describes the retinophorse as long curved cells filled with fine granu- 

 lar protoplasm and surrounding an axial nerve-fibre. The inner expanded ends 

 contain a minute vacuole and terminate at an undulating line of division or pseudo- 

 membrane (median limiting membrane) above the rod layer. The outer attenuated 

 ends are transformed at the periphery into fibres that turn and form the optic axis. 

 The most superficial of these describe long curves that bend at the expanded inner 

 end almost at right angles to terminate in the centre of the retina, while those at the 

 periphery describe semicircles almost. They thus form a saucer-shaped layer of 

 cells whose large nuclei are crowded to the periphery of the retina. This description 



