THE NERVE DISTRIBUTION IN THE EYE OF PECTEN IRRADIANS. 479 



for the retinophorse answers perfectly for the supporting cells of the median layer, 

 with the exception that the supporting cells do not contain axial nerve-fibres. In 

 some sections the axial nerves of bipolar cells appear to be in supporting cells, that 

 lie either above or below the bipolar cells, and it must have been these that Patten 

 mistook for the axial fibre of the retinophora, while the refractive vacuole at the 

 inner end of the cell must have been the refractive membrane and protoplasm of the 

 nuclei of the rod-cells, that lie, however, between the bases of the supporting cells. 

 The third elements in Patten's list of the parts of the anterior wall are the inner gan- 

 glionic cells. According to his description they are flat cells that form a single row 

 squeezed between the retinophorae. They send out several fibres toward the rod, the 

 largest of which extend over the surfaces of these structures, while on the outer side 

 two large fibres extend toward the lens and become continuous with the side branch of 

 the optic nerve. These ganglionic cells were mistaken by Hensen ('65), Carriere ('89), 

 and others for nuclei of the retinophorse. The inner ganglionic cells are in fact the 

 bipolar cells. They form a single layer between the supporting cells and send fibres 

 both toward the lens and toward the rods, but these fibres do not on the one side 

 continue with the side branch of the optic or on the other extend over the surfaces of 

 the rods. In sections stained by other means than methylen-blue they do have this 

 deceptive appearance. Since the large marginal ganglionic cells that give off fibres 

 to form the basal optic trunk and the rod-cells with their nuclei were not seen by the 

 other investigators, and since the character of the bipolar cells was unknown to them, 

 it is not strange that their descriptions and interpretations regarding these elements 

 should have been incorrect. It is almost impossible to obtain a true idea either of 

 the peculiar structure of the external ganglionic layer or of the distribution of its 

 fibres without the aid of some means like methylen-blue, which brings out distinctly 

 the nerve structure. Consequently it is not surprising that Patten and others 

 believed that several rows of two kinds of ganglionic cells formed the outer layer of 

 the retina, and that the broad ends of the outer cells terminated in many fibres that 

 penetrated the septal membrane to unite with the side branch of the optic nerve, while 

 their inner ends radiated inwards to terminate at the inner ends of the retinophorae 

 and rods. The outer row of cells (Fig. 3, gn. ex.) with broad ends that connect by 

 several fibres with the side branch of the optic nerve and send fibres inward to form 

 a network in the median and posterior layer over the bipolar and rod cells are the 

 true outer row of external ganglionic cells; while the inner row of cells (s.s/. a.) with 

 broad bases that lie proximal to the anterior limiting membrane are the anterior 

 supporting cells. Having passed in critical review the morphological elements of 

 the retina as described by different investigators, it seems that the retina is not so 



