54 
Examination of an Alhinotic Eye 
pigmented chrouiatophores are present in the choroid, the age of the foetus is given 
as 5 — 6 months and the eye measurements were 9 mm. E. Treacher Collins (5) 
measured the eye-balls of some human foetuses and found that at the fourth 
month, two eye-balls measured 8'5 mm. in the antero-posterior diameter, 8 mm. 
in the vertical, and 8 mm. in the lateral diameter. At the sixth month, two eye- 
balls measured 10'3 mm. in the antero-posterior diameter, 9'75 mm. in the vertical, 
and 10 mm. in the lateral diameter. According to these measurements, case No. 6 
would certainly not be older than 5 months. It is quite obvious from an ex- 
amination of these cases that the mesoblastic pigment in the eyes of dark races 
appears earlier and is laid down in foetal life in greater quantity than in European 
eyes. These notes refer only to the pigmentation of the choroid, ciliary body and 
iris, but mesoblastic pigment is conspicuous in some of the cases at other parts of 
the eye, such as along the course of the ciliary blood vessels in the sclerotic. 
D. General Conclusions. 
(o) Of the six albino eyeballs thus far examined, the albinos being determined 
clinically by the usual clinical characters, four are found to have pigment, of a 
fifth no statement was made by the examiner as to pigment. The sixth case was 
that of an infant, and here no trace of pigment was found in any of the structures 
of the eye. The remaining examinations of the human albino eye are concerned 
only with ])ortions of the iris ; in one no pigment, in the other some pigment, was 
observed. The former case provides no evidence as to whether the whole eyeball 
was or was not without pigment. We must conclude therefore that the total 
absence of pigment in the eye cannot be used as a definition of human albinism. 
{h) As apart from absence of pigment, the absence or imperfect developinent 
of the fovea centralis shown to occur in albinotic eyes may possibly be the chief 
cause of defective vision in these cases. 
(c) An examination has been made of the distribution of pigment in the eyes 
of a number of dark-raced individuals, adult, infant and foetal. The notes made 
indicate that in the dark-race eye mesoblastic pigment appears earlier in foetal 
life, especially in the choroid, and is in much larger quantity by the time of birth 
than in the European eye. 
According to this we should expect, if albinism consists of " an arrest of 
development," more pigment in albinos of dark races than in albinos of white 
races. Clinical examination of such albinos appears to indicate that this is a fact, 
but it is a fact which might be accounted for on other than the Meckel-Mansfeld 
hypothesis. At the same time it renders any definition of human albinism as a 
complete absence of ocular pigment less valid for any practical service in the study 
of the heredity of albinism. 
