140 
Dr, Butter on a peculiar Case of Vision, 
ing, judging of, comparing, and remembering (as confined solely 
to colours, his other faculties being perfect,) are deficient. We 
must seek the explanation, therefore, in physiological, and not in 
optical science, for the phenomena do not depend on the mecha- 
nical construction of his eyes. Yours, &c. John Butter. 
Observations cm the preceding Paper, By Dr Brewster. 
From the facts described in this very interesting paper, Dr 
Butter has concluded, that Mr B. Tucker’s imperfect vision of 
colours has a physiological and not an optical origin ; and he 
proceeds in the conclusion of his paper, (which, for obvious rea- 
sons *, we have omitted,) to fortify this conclusion by the state- 
ment, that Mr R. Tucker is particularly defective in the “ or- 
gan of colours.” 
In giving an account of the case of Mr Dalton, and others, 
whose eyes have an imperfect perception of colours. Dr Thomas 
Young has remarked, (in opposition to Mr Dalton’s opinion, that 
the vitreous humour of his own eye is of a deep blue tinge), 
that it is much more simple to suppose the absence or paralysis 
of those fibres of the retina which are calculated to perceive red.” 
With regard to the existence of fibres in the retina, suited to 
the perception of different colours, we have no evidence ; but it 
seems quite sufficient for the explanation of the leading facts, to 
suppose that the retina is insensible to certain colours. 
Dr Wollaston, in his interesting paper on sounds inaudible to 
certain ears has shewn, that ears, both of the young and old, 
which are perfect with regard to the generality of sounds, may, 
at the same time, be completely insensible to such as are at one 
or the other extremity of the scale of musical notes ; and I have 
lately ascertained, that some eyes which perform all the functions 
of vision in the most perfect manner, are insensible to certain im- 
pressions of highly attenuated light, which are quite perceptible 
to other eyes. Dr Wollaston has given the most satisfactory ex- 
* We have received various phrenological communications for insertion in this 
Journal ; but independently of the opinion which we entertain of this branch of 
modern study we could make no apology to our readers for inserting such ar- 
ticles, when we are obliged to omit one half of the papers that are sent to us on 
subjects of substantial science, 
f See this Journal') vol. iv. p. 158, 
