300 Anomalies of Pigmentation among Natives of Nyasaland 
In dealing with the pathogeny of the condition I follow largely Pearson in his 
presentation of various theories. The normal formation of skin-pigment is a 
question around which much conflicting opinion has grown. The site of the 
formation of the pigment has been variously supposed to be in cells belonging to 
any or all of the primary layers, endo-, meso- and ecto-derm. 
Special cells have been described as acting as carriers of pigment from one 
layer to another and called in consequence chromatophores (Kolliker, Simon, 
Kerbert, Ehrmann); Ehrmann later considered these cells to be actually the 
producers of the pigment, and calls them chromatoblasts or melanoblasts. 
Meirowski's summing up of Ehrmann's views quoted by Pearson is as follows: — 
(1) The production of pigment occui's in special cells, the melanoblasts, which 
are not identical with mesodermal or epidermal cells. 
(2) The melanoblasts are products of the middle germ layer, which in part 
further develop there, grow into the epidermis, and there have an independent 
cell existence. 
(3) The material which is converted into melanotic pigment comes from the 
blood and is haemoglobin. Haemoglobin is converted into melanotic pigment by 
the vital processes of the melanoblasts. 
(4) Extra-cellular creation of melanotic pigment is not yet demonstrated. 
True melanotic pigment only occurs in an extra-cellular form by the break-up 
of pigmented cells. 
(5) The transfer of pigment occurs by aid of protoplasmic flow along proto- 
plasmic threads, which connect the melanoblasts with the epithelial cells. For 
this reason this theory is not an " Einschleppungstheorie " but an " Einstromungs- 
theorie." 
(6) Pigment is, at least shortly after its production, a body dissolved in a 
highly fluid colourless substance. 
Unna believes that the pigment granules formed according to Ehrmann's 
hypothesis pass by way of the lymph stream to the epithelium. 
Cohn holds that free pigment certainly exists outside the cells. 
Schwalbe believes that epidermal and dermal cells can each produce granular 
pigment as a result of their individual activity, drawing upon the same source, 
though independently ; he believes that : (i) a pigmentation of the cutis can 
occur with completely unpigmented epidermis and hair, and (ii) a pure epithelial 
pigmentation can occur without trace of pigment in the underlying mesoderm. 
He rejects the chromatophore theory and considers these cells to be transformed 
epithelial cells. 
Kaposi also criticises Ehrmann's views to show that a haemoglobin origin for 
melanin is untenable. More recently other observers (Meirowsky, etc.) have come 
to the conclusion that epidermis and cutis pigment can arise independently, and 
