4 Golding Bird and Schäfer, 



books. In this diagram the fovea is represented as a broad and deep 

 depression of the internal limiting membrane, shapen like an old- 

 fashioned wide tea-cup, having the sides at an angle of 45 ^ and the 

 bottom nearly flat, and occupying about one -fourth of the whole 

 section of the fovea. This depression of the internal membrane nearly 

 abuts against a shallower but well marked pit formed by a depression 

 inwards of the external limiting membrane, upon which are set the 

 cones. These diminish in diameter towards the centre but show an 

 increase in length exactly corresponding to the depression upon which 

 they stand, so that the line of pigment cells is maintained at an even 

 plane without any depression of the external surface of the retina 

 being produced corresponding to that of the limitans externa ^). This 

 diagram therefore, like that of the chameleon's fovea given by Müller, 

 shows two depressions or foveae, inner and outer, with their convexities 

 directed towards one another. The interval between the two mem- 

 branes at this place is very narrow and is represented in Schultze's 

 diagram as being almost entirely filled by the cone-nuclei and by an 

 extension of the internal molecular layer, none of the other layers of 

 the retina being seen opposite the bottom of the cup, that is to say, 

 over one quarter of the diameter of the fovea. The cone-nuclei are 

 represented as forming a layer two or three deep, close to the limitans 

 externa. They appear as oval bodies and the fibres which are pro- 

 longed from them (cone-fibres) are delineated as very fine filaments 

 diverging obliquely towards the sides of the fovea. The inner granules 

 are shown as closely packed, round nuclei, forming a layer gradually 

 diminishing towards the middle of the fovea but sharply marked oft 

 up to its point of disappearance from the strata above and below it; 

 whilst the nerve-cells of the ganglionic layer are represented as ellip- 

 tical or spindle-shaped bipolar cells with their axes parallel to the 

 sides of the fovea. 



W. Krause-) also gives a representation of a section "durch 



') It is noteworthy that in the original drawings in the Arcli. f. niikr. Anatomie 

 Bd. II the cones which are set on this depression are not exactly vertical hnt their 

 outer ends tend to converge somewhat towards the centre so as to bi^ more closely 

 jiacked where they abut against the pigmentary layer. 



') .Mlgeraeine Anatomic. 1876. p. 168. 



