C. H. Usher 
51 
no differentiation, corresponding to the appearance of the niacida and fovea in a 
normal eye, and that the arrangement of the retinal blood vessels at this region 
was different from that seen in normal eyes, in that instead of converging regularly 
towards a fovea, the}' met and crossed each other irregularly. 
When a normal human eyeball is opened and examined macroscopically, a 
diffuse pale 3'ellow colour is visible in the retina at the macula. In albino eyes 
examined by Manz, Fritsch and Carron du Villards(2), no yellow was found at 
the macula, while in a case by Buzzi(l), and in the one already referred to by 
Nettleship, the yellow colour was present, as in this case. During life the yellow 
colour at the macula is not seen with the ophthalmoscope, when the usual sources 
of illumination are employed. Recently however Affolter(20), by using red free 
light, has been able to see the yellow colouration with the ophthalmoscope, but he 
failed to find it in two albinos' eyes. 
The imperfect vision in albinos has been explained by attributing it principally 
to the absence of pigment, or defective pigmentation, in the retinal epithelium, 
but the results obtained by histological examination of the macula in these few 
human albino eyes, and the records of the two cases with nystagmus, already 
referred to (aniridia and hereditary nystagmus), in which the fovea was absent, 
suggest another explanation, and pending further investigation of the macular 
region in the human albino eye, there is reason to regard the imperfectly developed 
or absent fovea as possibly the chief cause of the defective vision and nystagmus in 
albinos. 
C. On the Ocular Mesoblastic PiciMENTATioN of the Iris and Choroid 
IN SOME Dark-Race Eyes. 
The following eyes were examined : 
1. Tamil seven-months' foetus. Ej'es received from Dr H. Fraser, fi'om the 
Federated Malay States (Kuala Lnmpui-), November 30th, 1915. Iris stroma 
contains some pigment, even with a low magnification it is evident that the 
anterior layers of the stroma are lightly pigmented, and with high powers 
numerous brown granules are seen in both bodies and processes of the chroma- 
tophores. None of the lai'ge round dark cells so conspicuous in the adult dark- 
race iris are present. Ciliary body contains lightly pigmented chromatophores. 
Choroid has well pigmented cells at macular region. Further forwards the cells 
are not so well pigmented. 
2. Tamil seven-months' foetus. Eyes received from Dr H. Fraser, Federated 
Malay States (Kuala Lumpur), November 30th, 1915. The eyes are smaller than 
those of No. 1. In the iris stroma, only a few chromatophores are found containing 
pigment granules, and a few are present in the ciliary body. The choroid contains 
brown, round, pigment granules in the bodies and processes of the chromatophores, 
especially well marked at the macula (Fig. 2). None of the cells are so dark as 
those in an adult Tamil eye, and they become very lightly pigmented away from the 
macular region. The pigmentation is much greater in the choroid than in the iris. 
4—2 
