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which the hair may undergo. The question of positive colour is not here 
discussed, as there can be no doubt that colour is due to the pigment 
deposited in the cortex. Changes of colour are mainly dependant on 
functional activity of the papilla, that is to say, on the rapid growth of cells 
containing more or less pigment material, which can be deposited as the cell 
is metamorphosed into cortex-fibre ; in short, on the substitution of a new 
shaft for an old one by continuous growth. The removal of pigment from 
an adult hair shaft, either by absorption or circulation of any bleaching fluid 
is not the mode (as some suppose) in which the hair becomes white. The 
usual and natural permanence of colour, implies of itself a passive condition 
of the once formed hair shaft And the hair in this passive state is not 
liable to any resumption of activity. The rare and very exceptional instances 
of sudden whitening of the hair, by no means prove a sud den absorption or 
actual removal of the pigment. In accounting for the supposed sudden 
absence of colour it must be borne in mind, that the causes which usually 
produce it, are such as occasion not only excessive depression of mind, (horror, 
grief, &c.) but also powerfully influence all organic function, and annihilate 
for the moment, absorption and secretory action. This is not a state 
favourable to the assumption of such theories as the removal of the pigment 
or the influence of an imaginary bleaching process, such as the pouring forth 
of a fluid capable of acting chemically on colouring matter. On the contrary, 
the adult hair consists of dead matter, incapable of being permeated by a 
circulating fluid, and inaccessible to any but the constantly accompanying 
sweat or fatty secretion When a person perspires after the suddeu shock 
of mental distress or bodily danger, the effect is one of reaction, but even 
in this case the hair does not turn white. It is rather when reaction does 
not occur that the hair whitens. 
Accepting the stories of hair suddenly rendered white as facts, our first 
step towards explanation is obviously to ascertain by dissection and micro - 
chemical treatment whether any changes of texture, disposition, or physical 
condition of the affected hair have occurred, the causes of which could be 
traced to the psychical and corporeal malady. Whether this has been done 
satisfactorily by a competent anatomist or not (the opportunity is rare) I 
know not. But it may be, a priori, fairly conjectured that dryness and 
shrivelling of the hair bulb and shaft would be the first result of interrupted 
functional activity of the papilla and its accompanying sudoriferous and 
sebaceous glands. The shaft would be further exposed to the ordinary drying 
influences of the atmosphere, whilst the natural lubrication from the gland 
secretions was in abeyance. 
The raising of the cuticle scales by drying and the admission of air beneath 
them, would naturally follow a state of dryness of the surface, and the 
