On the anatomy of the fovea centralis of the human retina / by J. W. Hulke.

  • Hulke, J. W.
Date:
[1867]
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Licence: Public Domain Mark

Credit: On the anatomy of the fovea centralis of the human retina / by J. W. Hulke. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    3. VI. On the Anatomi/ of the Fovea Centralis of the Human Metina. By J. W. Hulke, F.B.C.S., Assistant Surgeon to the Middlesex and Royal London Ojjhthahnic Hos- 2)itals. Commtmicated by William Bowman, F.B.S. Received May 26,—Read June 14, 1866. The following account of the fovea centralis is chiefly drawn from a study of this part in a perfectly healthy eye excised during life (in order to allow the extirpation of a tumour) and instantly put into a solution of chromic acid. By instantly hardening the retina, the formation of the Pliea and the resulting disturbance of the fovea were pre- vented, and it was possible to make extremely regular sections. The fovea centralis is a minute circular pit in that central spot of the retina called, from its yellow colour, the macula lutea—yellow spot. This colour* proceeds from a diffuse stain of the retinal tissues, and not from the presence of granulated pigment as in the choroid. It is most intense at the centre of the spot, and fades towards the cir- cumference of the spot, where it ceases gradually without a distinct margin, so that neither in the fresh retina nor in that which has been artificially hardened in chromic acid (which destroys the colour) can we use this as a measure of the extent of the spot. The size of the spot is, however, more certainly fixed by the extent of certain anatomical peculiarities which do not occur in any other part of the retina. The ophthalmoscopic appearance of the spot in the living eye is that of an ellipse, the major axis of which is horizontal. It is rather larger than the disk of the optic nerve, and comes into view when the eye under observation looks directly at the sight-hole in the mirror. It is distinguished from the parts around by its deeper colour and by a certain dullness, difficult to describe but readily appreciated when seen, which proceeds from the faintness or absence of the reflection occurring at the inner surface of the retina elsewhere. In children, particularly in tliose of dark complexion, the retinal reflection ceases at the periphery of the macula with such a definite edge that the macula appears as a dull, dark-coloured spot encircled by a bright ring. In the middle of the macula lutea a bright dot marks the position of the fovea centralis. According to Helmiioltz the visual Hue (the straight line which joins the most sen- sitive part of the retina and the object directly seen) does not coincide witli the axis of the eyeball, as is commonly thought, but includes an angle with it; and the most sen- sitive point in the retina (the fovea) lies slightly outwards, and usually a little below the posterior end of the axis of the globe*. In an artificially hardened normal eye, in which the relations of the parts were undis- * Cornelius, 'Die Tlieorie des Sehcns unJ riiumlichcs Yorstellcns.' HaUe, 1S61, Abth. 1. S. 230. MDCCCLXVII. Q