D. Macdonald 
15 
nations have shown that among other defects in the internal ear of such cats the 
walls of the perilymph chamber lack pigmentation. In a recent histological 
examination* of a case of albinism, in a child aged ten weeks, no abnormality 
was found save a complete absence of pigment in the brain, eyes, internal ear, 
suprarenal gland, skin and hair. Commenting on this case, Pearson f refers to an 
interesting suggestion. ..He remarks that the disappearance of superficial pigment 
is one of the marks of senility, that it affects the hair and eyes alike. Is it possi- 
ble, he asks, that this loss of superficial pigment can ever be accompanied by a loss 
of internal pigment, possibly in the case of the brain centres ? Senile imbecility, 
and in its milder form senility, might possibly be associated with a weakening of 
the intensity of pigmentation in certain of the brain centres. Is it conceivable 
that any forms of imbecility are associated with defective brain pigmentation ? 
Ophthalmoscopic investigation shows a high percentage of incomplete albinism of 
the eye in the insane. Pearson also suggests that the lack of pigmentation in 
the internal ear as shown in the albinotic cat might possibly be associated with 
deafness. 
This association of pigmentation with certain classes of disease seems not 
unreasonable when it is considered that the ectoderm gives rise not merely to the 
hair and epidermis, but also to the whole central and peripheral nervous system 
and other important structures. 
The endogenous pigments of the body may be divided into two groups, haemo- 
globin and its derivatives and other metabolic pigments. The former is outside the 
scope of this investigation; of the latter the most important group is the melanins. 
These are dark, black or brown and reddish brown pigments, and exist normally 
in the hairs, the choroid coat of the eye, the deeper cells of the malpighian layer 
of the skin, in the chromatophores of the upper layers of the corium and also in 
the membranes of the brain, especially in the neighbourhood of the choroid plexus. 
The normal production of melanin in members of the human family has its 
extremes represented by the fair-haired Saxon and the swarthy negro. The differ- 
ences in colour here are due, not to the presence or absence of the cells themselves, 
but to variations in the amount of pigment therein deposited. In this respect, 
therefore, the negro differs physiologically rather than anatomically from the 
European. 
A physiological increase in the pigmentation is observed also in pregnant 
women, even among the fair, and is most marked in brunettes ; a similar pigmen- 
tation is observed in many cases of exophthalmic goitre and in certain neurotic states. 
What is regarded as a pigmentation of the same order is met with in Addison's 
disease. This condition is generally held to be an affection of the abdominal 
sympathetic system, induced most commonly by disease of the suprarenal bodies. 
The medulla of the suprarenal body is produced by an ingrowth of cell groups 
* J. E. Adler and J. Macintosh : " Histological Examination of a Case of Albinism." Biometrika, 
Vol. vii. p. 237. 
t Pearson : " Note on Internal Albinism." Biometrika, Vol. vn. p. 246. 
