206 
HISTOLOGY OF ANIMALS. 
pil 
\ OrCS £ i 
a, pigraentum nigrum of a 
black Rabbit, b, cells from the 
choroid of a white Rabbit in 
which the pigment is wanting. 
plainly seen. In Albinoes, that is in the white offspring 
of black parents, the hexagonal cells are present, but 
F ig. 154. the pigment is so small in 
quantity as to allow the vas- 
cular choroid to be seen 
through the pupil, giving a 
pink appearance to the eyes 
of these people. The same 
may be said of white Rab- 
bits and Cats. A portion of 
the pigmentum of the choroid 
of a black Rabbit is repre- 
sented in Fig. 154, a, the 
cells are full of granules, and similar cells from a white 
Rabbit , in which the pigment-granules are either absent 
or void of colour, are shown at b ; the eyes of these 
animals are, from this circumstance, more or less pink. 
In the jpigmentum nigrum from the eye of a foetus, 
the cells are not only smaller 
than those of the adult, but 
the granules also are fewer 
in number, and the centre of 
each cell is occupied by a 
large white spot, the nucleus. 
A portion of this pigment, 
as seen under the same mag;- 
o 
Pigmentum nigrum from the nifying power as that of the 
eye of a human foetus: a, cells , 
magnified 250 diameters, b, por- adult, 111 Fig. 152, B, IS F6- 
tion of the same magnified 600 . . 
diameters. presented in rig. 155, a, and 
