250 DE. HUBEET A1EY ON A DISTINCT FOEM OF TEANSIENT HEMIOPSIA. 
It is quite inconceivable that the blood-vessels of one retina should be disposed in 
perfect unsymmetrical correspondence with those of the other (the left side of one 
agreeing- with the left side of the other, and the right with the right) ; and in fact they 
are not so disposed. And even if they were, and if the phenomenon were due to their 
disturbance, its spread would be ruled by geometrical radiation from the punctum caecum, 
where nerve and vessels enter the eye, not from the ‘ yellow spot ’ at the centre of vision ; 
and we should have two unconformable spectra, one on each side of the centre, perhaps 
overlapping, but certainly not coinciding, since the puncta caeca are not corresponding 
points in vision. 
Sir David Brewster’s experience seems to differ a little from Dr. Wollaston’s, the 
“shaded darkness” of the latter contrasting with the words “neither darkness nor 
obscurity ” of the former ; yet I think they are describing the same affection. The 
difference was probably due to the different circumstances of light &c. under which the 
observations were made. Wollaston was in the full light of the open air; Brewster 
speaks of his severe attacks as brought on by reading the 4 Times,’ probably therefore 
in his study, or at least indoors. 
I believe Brewster’s is the earliest mention (except Dr. Parry’s) of the self-luminous 
state of the parts affected, when observed in a dark room, and of the sensibility to general 
impressions of light which they retain. 
Sir David Brewster’s paper in the Philosophical Magazine gave occasion to another 
paper in the same Journal (Phil. Mag. Julyl865, vol. xxx. p. 19) by the Astronomer Boyal, 
who adds many particulars of great interest, and gives us a vivid picture in place of the 
imperfect sketches of previous writers. Indeed it is difficult to avoid the belief that we 
are dealing here with a new form of the disease. The outward spread of the cloud, its 
arched shape, its serrated outline, with smaller teeth at one end than at the other, its 
remarkable tremor, greater where the teeth are greater, its “ boiling,” its tinge of scarlet, 
and its sequel of partial aphasia and loss of memory, are all new features, not mentioned 
by any previous observer, but most important for the identification of the complaint Y 
This form of hemiopsia is the one to which I desire chiefly to direct attention, the one 
which I am able to illustrate from my own experience. 
A translation of Professor Airy’s paper appeared in 4 Les Mondes ’ (April 16, 1868), 
and not long afterwards he received a letter (April 24, 1868) from Professor Dufour, 
of Lausanne, from which I extract the following : — 
44 C’est avec un interet particulierement vif, que j’ai lu cet article : car j’ai ete plusieurs 
fois atteint de 1’afFection optique que vous decrivez. Jusqu’ici, j’en avais parle a deux 
medecins qui n’ont pas paru connaitre ce cas curieux, et je me figurais qu'il s’agissait 
d’un accident auquel seul j’etais sujet. Yotre description de l’hemiopsie decrit si exacte- 
* I am able to add, from later information, that in my father’s case the phenomenon exhibits conspicuous 
luminosity in a dark room. 
