Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29465/1463/
VISION. U53 
ally the expressionDaltonian” may be used 
for the sake of brevity. 
Modifications of insensibility to colours 
exist in every degree, and in the minor shades 
are so frequent as to be almost proverbial 
with reference to the male sex ; indeed, if 
twelve men, taken at random, were shown a 
numner of ribands of the more delicate 
colours, a diversity of opinion would almost 
certainly arise as to the appropriate names. 
The number of persons who cannot distinguish 
certain colours is considerable ; but the defect 
is seldom known to others, those who are con¬ 
scious of their imperfection being desirous of 
concealing it, and some perhaps, not being 
aware of it till accident leads to its discovery. 
In every case that has fallen under our notice, 
there lias been reluctance to submit to ex¬ 
amination, from the fear of ridicule ; and 
indeed it is difficult to repress a smile when a 
person is seen to match green and scarlet to¬ 
gether, or crimson and dark blue, and earnestly 
protest that the colours are absolutely iden¬ 
tical. The nearest approach to this condition 
in the healthy eye, and a test by which the 
embarrasment of Daltonians may be judged of, 
is the difficulty of distinguishing between blue 
and green by candlelight ; a difficulty which 
every one must have experienced. Analogous 
to this defect of the organ of vision, is that 
better known, because more evident, insensi¬ 
bility of the organ of hearing, whereby many 
persons are utterly unable to detect the differ¬ 
ences between musical notes, or, as pointed 
out by Dr.Wollaston, their ears maybe abso¬ 
lutely insensible to sounds at one extremity of 
the scale. Sir David Brewster remarks* that, 
although his own hearing is perfect and each 
ear equally acute for all ordinary sounds, yet 
one of them is absolutely deaf to the chirp of 
the cricket, while the other hears it distinctly. 
Dr. Pliny Earle has published + a remarkable 
illustration of the imperfection of the two 
senses in conjunction. “ The whole family 
(says he) of which the chart has been ex¬ 
hibited, is probably no less generally charac¬ 
terised by a defective musical ear than an 
imperfect appreciation of colours. * Several of 
the individuals comprised in it are utterly inca¬ 
pable of distinguishing one tune from another. 
* * A gentleman who has the general defect 
under discussion, and whose case is included 
in the thirty-one herein mentioned, is a well- 
known professor in one of the Metropolitan 
Medical Schools of the United States. In 
him the total inability to discriminate between 
musical sounds is coexistent with the defec¬ 
tive perception of colour * * Another 
of the gentlemen whose case of defective per¬ 
ception of colours is herein noticed, is gene¬ 
rally acknowledged as one of the first and 
greatest of American poets now living. He 
also is unable to distinguish one tune from 
another ; yet his poetry is not deficient in the 
requisites of perfect cadence, harmony, and 
rhythm.” 
* Philosoph. Mag. vol. xxv. p. 136. 
f American Journal of Medical Sciences, vol. 35. 
p. 347. 
It has been remarked by Wartmann as a 
curious fact, that in no ancient author is there 
any passage which can be referred to the 
subject of achromatopsy, and that the nume¬ 
rous travellers who have traversed the old and 
new world are equally silent in this respect. 
As to the relative frequency of achroma¬ 
topsy, Seebeck states that five out of forty 
youths who composed the two upper classes 
in a gymnasium at Berlin, were affected with 
it, and Prévost has declared that the pro¬ 
portion of this imperfect vision to perfect 
vision, is as one to twenty. It is true that 
Chelius and Chevreul entertain a very op¬ 
posite opinion, .but the balance of authority is 
decidedly against them. 
This affection is often hereditary, and is 
found in some families to a remarkable extent. 
It sometimes occurs in successive generations, 
of which a remarkable instance has been pub¬ 
lished by M. Cimier *, and at other times it ap¬ 
pears in alternate generations, descending far 
more frequently on the maternal side than the 
paternal. In the case of Mr. Milne, recorded 
by Dr. Combef, the maternal grandfather was 
affected with Daltonism, also his two brothers 
and a second cousin. In that of a child related 
by Dr. Nicholl J the maternal grandfather and 
several of his brothers were similarly affected ; 
such was also the case with two young men 
mentioned by Dr. Cornaz.ÿ They were the 
offspring of the same mother but by different 
fathers, and in both, achromatopsy existed to 
a marked degree. But the most striking 
illustration of the hereditary character of this 
defect has been recorded by Dr. Pliny Earle ||, 
and it is so remarkable that we give it in 
his own words. « My maternal grandfather 
and two of his brothers were characterised 
by it, and among the descendants of the first 
mentioned, there are seventeen persons in 
whom it is found. I have not been able to 
extend my inquiries among the collateral 
branches of the family, but have heard of one 
individual, a female, in one of them, who 
was similarly affected.* * * Nothing is known 
of the first generation (of five) in regard to 
the power of perception of colours. In the 
second, of a family consisting of seven 
brothers and eight sisters, three of the 
brothers, one of whom, as before mentioned, 
was the grandfather of the writer, had the 
defect in question. In the third generation, 
consisting of the children of the grandfather 
aforesaid, of three brothers and four sisteis, 
there was no one whose ability to distinguish 
colours was imperfect. In the fourth genera¬ 
tion, the first family includes five brothers 
and four sisters, of whom two of the former 
have the defect. In the second family there 
was but one child, whose vision was normal. 
In the third there were seven brothers, of 
whom four had the defect. In the fifth, seven 
sisters and three brothers, of all of whom the 
* Annales d’Oculistique, tom. i. p. 417. 
t Transactions of Phrenological Society, p. 222 
t Med. Chir. Trans, vol. vii. p. 477. 
§ Annales d’Oculistique, tom. xxiii. p. 43. 
|| Op. cit. p. 349.
        

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