230 



On the Minute Anatomy of some of the Parts concerned in 

 the Functions of Accommodation to Distance, with 

 Physiological Notes. By John Denis Macdonald, 

 M.D., r.R.S., StaiF-Surgeon H.M.S. " Fisgard." 



(Communicated by the Director-General of the Medical Department of the 



Navy.) 



No organ in the body exhibits more beauty of construction 

 to unravel, or more interesting physiological problems to solve, 

 than the eye ; and it is no wonder, notwithstanding the great 

 advances of modern science, that much room should still 

 remain for the improvement of our knowledge of its minute 

 anatomy, and the function subserved by every part in the 

 economy of vision. It would be quite impossible within the 

 limits of a few pages to deal with a twentieth part of the facts 

 and views that have been advanced from time to time in 

 relation to the subject of the present paper. Nor would that 

 be the writer's intention, though it were possible, being 

 merely desirous of making known some few anatomical par- 

 ticulars which do not appear to have been hitherto noticed, 

 and of associating these with the function of accommodation 

 to distance. 



We commence, then, with the conjunctiva, though it is not 

 immediately engaged in adaptation. As soon as we have 

 traced this membrane to the margin of the cornea we may 

 readily follow the epithelial coat over that structure, but the 

 basement membrane in this locality is generally believed to 

 be represented by the anterior elastic lamina of Bowman. 

 The intimate union of the conjunctiva with the cornea is 

 noticeable not only in dissection but in the pathological 

 condition known as chemosis, in which, by intelligent design 

 as obvious as any that can present itself in the eye, effusion 

 of fluid is prevented from encroaching upon the domain of 

 the cornea. The tying down of the deep surface of the 

 anterior elastic lamina3 to the cornea proper by oblique and 

 decussating fibres, first described by Mr. Bowman, would, 

 according to the present view, sufficiently explain the close 

 union above noticed; but in the eye of the ox or of the 

 sheep, in which an anterior elastic lamina is not demonstra- 

 ble, are we to assume that there is no basement membrane 

 between the cornea projDcr and the conjunctival epithelium? 

 In a late series of investigations made with the view of 

 settling this point, the writer has been quite satisfied of the 

 existence of a delicate basement membrane in the locality 



