270 Notes on the Pigmentation of the Human Iris 
lower half, the lower containing the tumour. The upper half was used for the 
sections, which were cut antero-posteriorly from near the horizontal meridian. 
Four figures will suffice to demonstrate the important appearances which may 
be followed all through the series of sections. 
Fig. I. (x Zeiss A. unstained.) 
Low power unilateral view of a section through the pupil, showing the dark 
brown posterior pigment epithelium, which increases in thickness near the pupil 
(behind the pupillary zone); in this region also, the stroma is seen to be thickly 
strewn with pigment cells, many rounded and full of pigment granules ; towards 
the anterior surface these rounded pigment cells are less numerous, some 
appearing to have ruptured, while at the anterior surface, the pigment consists 
almost entirely of yellow granules, the cells apparently having distributed their 
pigment in a granular form, thus causing the pupillary ring. The anterior surface 
of this pupillary region is seen to be distinctly yellow in colour. In the median 
and peripheral regions of the iris, beyond the pupillary area, very few pigment 
cells are seen although in no part are they entirely absent ; the anterior surface 
of these median and peripheral parts, which to external examination before 
enucleation appeared blue and free from anterior pigment, is yellowish and shows 
the presence of pigment granules, although more faintly than in the pupillary 
region. It will be noted also that near the pupillary margin, the dark brown 
posterior pigment epithelium passes suddenly and abruptly into the yellow colour 
of the anterior pupillary ring, also that the stroma of the pupillary margin has 
fewer pigment cells than the stroma behind the middle of the pupillary pigment 
ring. Towards the left limit of the field a dark brown anterior pigment spot 
is seen, as if some of the pigment cells had apparently passed through the stroma 
and located themselves on the anterior surface. In the stroma behind this spot, 
one or two disintegrated pigment cells appear with granular pigment around. 
Fig. II. (x Zeiss A. unstained.) 
Horizontal antero-posterior section through the pupillary margin. 
At the mid-point of the section corresponding to the pupillary margin few 
stroma pigment cells are seen, while on each side in the parts corresponding to the 
stroma behind the pupillary pigment ring they are numerous. The yellow 
anterior surface is most distinct opposite the parts of the stroma which have 
most pigment cells. 
Fig. III. (x Zeiss D. unstained.) 
Horizontal antero-posterior section above the level of the pupil through the 
yellow-brown pupillary zone. 
Note the dark pigment epithelium, and the stroma thickly strewn with 
pigment cells, which tend to disintegrate towards the yellow anterior surface, 
where pigment mostly in the granular form is seen. 
