The nature of the intra-ocular fluids / by W. Stewart Duke-Elder ; being the Sir Francis Laking Prize, 1926-1927, from the Biochemical Department, St. George's Hospital London.

  • Duke-Elder, Stewart, Sir, 1898-1978.
Date:
1827
Catalogue details

Licence: Public Domain Mark

Credit: The nature of the intra-ocular fluids / by W. Stewart Duke-Elder ; being the Sir Francis Laking Prize, 1926-1927, from the Biochemical Department, St. George's Hospital London. 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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    protracted and often acrimonious discussions of unnecessary hypotheses, with defective and confused experiments based on unsound physiological reasoning, with a multitude of theorizings and a paucity of facts. The present paper is an endeavour to point out the principles through whose neglect this disagreement has arisen, and to suggest what may approach more nearly the solution of a problem which forms the obvious preliminary to an inquiry into the nature of the intraocular fluids, and of the mechanism of their pressure changes. I. The Ocular Circulation It will simplify the subsequent discussion to consider at the out- set two questions which are of importance throughout the following pages : the comparison of the vascular supply of the eye in man and in the lower animals, and the comparison of the uveal and the retinal circulations. While in man the blood supply to the eye is derived whollv from the internal carotid artery, in the lower animals it arises from the external carotid. In the lower mammals, such as are used for experimental purposes (dog, rabbit, etc.), the transition stage between the two types occurs, and, although variations are frequent, as a general rule two ophthalmic arteries are present, one derived from either source, with a free anastomosis between them (Henderson, 1903; Parsons, 1903; etc.). The corresponding blood pressures in the various organs of the higher animals are generally accepted as comparable with those of man, but in considering the ocular circulation there may be some legitimate hesitancy in transferring experimental findings obtained in laboratory animals to the case of the human eye owing to the anatomical differences between the two. While it is very probable that they are approximately the same and in every way comparable, it would seem that the difference, if any, will be in the direction of a higher pressure obtaining in the ocular arteries of man. In him the ophthalmic artery is a direct branch of the internal carotid, virtually of the circle of Willis, a vessel which may be considered as the master vessel of the body inasmuch as the whole vasomotor mechanism is adjusted to maintain it continuously at a high pressure level. Immediately after this branch is given off the internal carotid constricts : its diameter proximal to the branching off of the ophthalmic artery averages 5.4 mm., immediately beyond this point it narrows to 3.8 mm., while the diameter of the ophthalmic artery averages only 1.5 mm. (Whitnall, 1921). The narrowing is therefore out of proportion to the cross section of the vessels, a provision which, by reducing the calibre of the main vessel and damming up the blood stream, will favour the passage of blood down this important branch, and ensure a high pressure in it.