Observations on the structure of the central fovea of the human eye / C. H. Golding Bird and E. A. Schäfer.

  • Cuthbert Hilton Golding-Bird
Date:
[1895]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the structure of the central fovea of the human eye / C. H. Golding Bird and E. A. Schäfer. Source: Wellcome Collection.

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

    14/32 page 12
    length of the outer segments, for although the general outline of the layer which they form is well marked and fairly sharply defined (PL I. Fig. 2), it is evident, from other specimens of the fovea in which these structures have been better preserved, that the outer segments are much longer than there shown. If they are to be assumed to have been in the unaltered condition long enough to compensate for the dipping in of the external limiting membrane at the fovea, the cones would have to measure in total length no less than Oi 33 mm. which is much longer than any that have been measured by previous workers1). In diameter also the outer segments are nearly if not quite as thick as the inner segments, so that they appear in well preserved specimens closely packed and with their outer ends some- what inclined towards the centre. It is obvious from this figure and from the photographs upon which it is based that either the accounts and delineations which have been given by former observers are largely erroneous or that there is, as H. Miiller supposed, great individual variation in the central fovea of the human eye. Whatever be the explanation it must be stated that it is a much more difficult matter than would at first sight appear to obtain irreproachable sections through this part. The retina is^ singularly liable to be thrown into folds just here after death due no doubt to its imbibing fluid from the vitreous humour. If to obviate this the vitreous is completely removed the retina is thereby liable to be mechanically injured. Considering that histologists are not usually in a position to obtain a normal human eye instantly alter removal from the body, it is probably therefore only very rarely that a section passing indubitably through the very centre ol a well-pre- served human fovea has actually been obtained. Schwalbe, who is with justice regarded as the first authority on the structure of the eye and who has devoted much attention to the retina in particular, has as we have seen been compelled to fall back for the description of this part upon a single specimen sent to him by another observer and that one a section passing according to his own statement not
    digitised image 1
    digitised image 2
    digitised image 3