75 



seen extending from the connective tissue to the cavity 

 of the eye (fig. 47. Ret. c). They possess spherical 

 nuclei in which may be seen a nucleolus and numerous 

 granules, and their distal portions are lost in a mass of 

 dense black pigment. 



Between these large cells are to be found a number of 

 compressed nuclei (fig. 47, Nuc. int. C), which stain more 

 darkly than those above mentioned, possess finer granules, 

 and in short cannot be mistaken for the nuclei of the 

 large cells. These nuclei belong to slender fusiform cells 

 which are interpolated between the larger ones and whose 

 boundaries are difficult to follow in sections. If the eyes 

 are macerated in a 4 per cent, cocaine solution in sea- 

 water, the true shape of the structures building up the 

 retina becomes at once apparent. The large cells possess 

 the extraordinary shapes indicated in fig. 48. It will be 

 noticed that they are widest towards the base, and that 

 the nucleus is in general situated not far from that region, 

 in fact, somewhere near the centre of the cell. One of 

 the most curious facts is the prolongation of the cell into 

 processes, of which there may be several (fig. 48, pr.). 

 The apex of the cell is rounded and contains a large 

 quantity of black pigment (fig. 48, Pig.) in the form of 

 minute granules closely crowded together. Very often, 

 too, this rounded distal extremity bears a prominence 

 which may be taken as the remains of the " Stiftchen " 

 or hair-like processes seen in sections and mentioned 

 below. The narrow cells also possess pigment, so that 

 there is no differentiation here into pigmented and 

 pigmentless cells. 



The cavity of the optic vesicle is filled with a 

 structureless gelatinous mass, which forms a lens (fig. 47, 

 Lens). This lens does not possess a perfectly rounded 

 contour where it abuts on the retinal cells, but is indented 



