Eyesight, good & bad : a treatise on the exercise and preservation of vision.

  • Carter, Robert Brudenell, 1828-1918.
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: Eyesight, good & bad : a treatise on the exercise and preservation of vision. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    opening both above and below. These fibres collec- tively form the muscle which closes the lids, and which is named the orbicularis by anatomists. The upper lid is raised or held open by another muscle, the antagonist of the orbicularis, which passes along the roof of the orbit from the bones of the skull, and is inserted into the whole length of the upper border of the cartilage ; but the lower lid sinks to the open position by its own weight, as soon as the action of the closing muscle ceases. This muscle is not only called into action during sleep, or to shut the eyes designedly, but also for the performance of that very frequent involuntary closure and re-opening of the lids by which the surface of the eyeball is moistened, and freed from particles of atmospheric dust or other impurity ; a provision which is of the highest importance for the preservation of the polish and transparency of the cornea. From the outer borders of the lids spring the eyelashes, which afford protection against the entrance of coarse dust, insects, and other foreign bodies or intruders ; and, immediately within the eyelashes, on the very margins of the lids, are the openings of numerous fat glands which are situated in the substance of the cartilage. These glands, which are called Meibomean, after the name of their discoverer, furnish a greasy secretion which lubricates the edges of the lids, and which acts as a barrier to the escape of moisture from the eyes over the cheek. The free mobility of the lids over the eyes is per- mitted by the conjunctiva, which, after lining the lids as