Sent from Karl Pearson
22 Sep 1911
Description:

‘My dear Nettleship,

I do not think I have ever pledged myself to any definition of albinism which asserted that asserted that these keratin(?) colouring matters were to render an albino incomplete. I take it that pigment in hair means the possession of granular pigment which is melanin. I do not think that diffuse pigment could ever give the effect of dark hair. When we say that hair has “diffused pigment” it invariably means what is left after long soaking in alcohol and this diffused pigment is never dark but of a yellow or red transparent colour. The darkest forms of it occur in the red hair of certain human albinos – the rufous[?] albinos, in the fawn patches of some Japanese mice and in the fawn yellow of the Pekinese. You will remember that in our chapter on hair we show that certain fawn Pekinese have apparently normal eyes, but no melanin pigment, only this diffused pigment in the coat. We tried other red & fawn dogs, but did not find this to be the cases, hence there is some evidence to explain why albinism is more likely in the Pekinese than other breeds. Every coloured Pekinese has of course diffused as well as granular pigment, and I take it most normal human hair. Nearly all albinos show this diffused pigment, i.e. have a cream or yellow tint in hair. If you take Cornaz’s Therèse[?] Rey, of whom Usher bought back two large locks of hair – she was eighty something – one was absolutely white & the other silk-worm silk yellow. I should like to show you those. You yourself in the pedigrees have termed complete albinos many of the native albinos with hairs yellow or reddish macroscopically, but these hairs have no granular pigment.

I should be very glad to examine Fo’s skin when you have a chance of sending it, and seeing what I make of it.

My point is that I doubt whether the spectacle mark is really much darker in diffused pigment when it has been completely washed than portions of the ear hair, and that if it is I am inclined to attribute it to a dyeing effect of the discharge of the eye, which alcohol does not wash out. A similar effect even arises from discharge between the paws & from the mouth, but to less extent.

If you look at p. 5, 6, & 4 of the Albinism, you will see that initially we did not lay stress on yelow tint in hair rendering albinism incomplete. Now I should not like to say dogmatically that the presence of diffused pigment is wholly unconnected with granular pigment, yet[?] the chemical relation of these keratin(?) to the melanin substances is not yet clear, and we have men speaking of “white melanin” [NB: see Spiegler, Ross Aitken Gordner, Am. Nat, 1910.], but I think as far as the hair is concerned the absence of pigmentation granules is the key to the situation, and even this is quantitative for the granules get fewer & fewer & smaller & smaller, till you hardly know if they exist or not.

Before I saw Coats[‘] report on the Japanese mouse and the Russian rabbit, I should have said that this mouse & rabbit were complete albinos of the eye, because the pink of these rabbits’ eyes & mices’ eyes is not distinguishable macroscopically from that of the white mouse. I want to start breeding ‘white’ mice to test whether their eyes are always “completely” albinotic. As a boy I had hundreds & the ‘blood red’ eyes were not infrequent. More recently breeders have told me that they appear in pure white mouse stock, and that is what I should like to investigate. A sufficient number of albino rabbits’ & mices’ eyes have not been examined yet for us to assert, that they are always free of all pigment. That is just what everybody says now of Japanese mice’s eyes, but we know them not to be. I give you Adler and McIntosh’s baby, but surely it is very poor evidence for the sweeping statement of the general character of white race albino eyes. I enclose Coats’ letter [not present]. I should rather like it when revising their reports because they speak several times of “cellular pigment” which is vague.

I return your letter as desired. I hope I have put my points definitely. I enclose proof of the hair chapter, but I have only these copies so please return them soon, you may like to see exactly what has been said about Pekinese hair.

You sent me back the specimen of Yang Ren’s tail hair, but not that of Tin[?] Lo. I can cut another piece off, but I have rather spoilt her tail with the first clip. If you come across it, will you let me have it?

Yang ren’s arrived yesterday alone in an envelope without  letter.

I have got specimens of Ah Cum’s hair but not yet heard about Meh’s.

I think you will find if you look up the references that we actually rejected the definition of no pigment in dermal & ocular tissues as basis of “perfect albininsm.” At least I always thought we had.

I enclose some account of my dogs there is no weighing machine here or you should have their weights. Please pick out what you think of interest. It is not of much value, because I don’t know the normal breed.

[... continued overleaf ? – not present in archive photographs...]’