190 Mr. Hulke on the Anatomy of the Fovea centralis. [June 14, 



4. The bacillary layer contains only cones in the fovea, but rods in ad- 

 dition towards the periphery of the macula lutea. 



5. The cones and rods in the macula are longer and more slender than 

 at a distance from it. Although the greater slenderness is more apparent 

 in the cones, yet the most slender cones are stouter than the rods. 



6. In both cones and rods an inner and an outer segment are discernible, 

 and both segments consist of a sheathing membrane and contents. In the 

 outer segment the contents do not exhibit any indication of structure. 

 The inner segment, where its dimensions permit, contains an "outer 

 granule/* and is always produced in the form of a fibre, which connects 

 the cones and rods with the inner layers. These I have called the 

 primitive cone- and rod-Jibres, collectively primitive bacillary fibres. 



(KolHker, in the last edition of his * Handbuch der Gewebelehre,' re- 

 stricts to these the term '* Mutter's fibres,'' which was originally exclu- 

 sively, and is still very generally given to the vertically radial connective- 

 tissue fibres first described by H. Miiller.) 



7. An outer granule is intercalated in each primitive bacillary fibre, 1st, 

 where the inner bacillary segment is too slender to include the granule, 

 and, 2nd, where the segment is associated with a distant granule. This 

 kind of connexion always obtains with the rods, and with the cones at the 

 centre of the fovea. 



The outer granules which belong to the rods are not distinguished from 

 those which belong to the cones by any constant characters. 



8. The primitive bacillary fibres run obliquely from the outer towards 

 the inner surface of the retina, and radially from the centre of the fovea 

 towards the periphery of the macula lutea. 



9. They form a very conspicuous obliquely fibrillated band, lying be- 

 tween the outer and the inner granule-layers, in which the primitive fibres 

 combine in bundles which have a plexiform arrangement. This band cor- 

 responds to that band which in the chameleon's retina I called the cone- 

 fibre plexus. Miiller and KoUiker call it the intergranule-layer. 



10. Between the inner surface of this layer and the inner granule-layer, 

 there is a thin granular band of finely areolated connective tissue, through 

 which the bacillary fibres pass into the inner granule-layer. It is in part 

 derived from the terminal divisions of the vertically radial connective-tissue 

 fibres, and it answers to the band which in the chameleon I termed the 

 intergranule-layer. 



11 . In the inner granule-layer two kinds of granules are distinguishable, 

 nuclei and nucleated cells. Both are in connexion with the oblique bacil- 

 lary fibres, which in this situation are exceedingly delicate, and require a 

 high magnifying power and a good section for their demonstration. 



12. The connective-tissue fibres (generally known as Miiller's radial 

 fibres), which traverse the retina in a vertically radial direction from the 

 membrana limitans interna towards the outer surface, are very conspicuous 

 in the inner layers, where in sections transverse to the direction of the 



