1905.] 



On the Production of Intraocular Fluid. 



304 



Cat, anaesthetised with Ether. Eserine applied locally to conjunctival sac. 

 Pupil moderately contracted. 



Another disturbing factor is the size of the pupil. We shall have to 

 consider this factor more in detail later on, but unless atropin be given at 

 the beginning of the experiment, the observations on the living eye are made 

 with a somewhat contracted pupil, whereas those on the dead eye are 

 made on a widely dilated pupil. Other factors being equal, the filtration in 

 the eye with dilated pupil is always slower than in the eye with contracted 

 pupil. In certain of our experiments we observed an equality of inflow 

 between the dead and living eye at some pressure above 40 mm. of 

 mercury, but on further raising the pressure this equality disappeared, 

 showing that we were dealing with yielding tissues and altering membranes. 

 This fact rendered it impossible to obtain by such methods any definite 

 information of the intracapillary pressure in the eye-ball, or of the 

 level of intraocular pressure at which transudation or formation of intra- 

 ocular fluid would definitely cease. One other factor which would aid 

 in disturbing the results obtained is the effect of a high intraocular 

 pressure on the general circulation through the eye-ball. If we succeed in 

 raising the pressure to such a height that the circulation is entirely abolished, 

 changes must rapidly take place in the apparatus both for formation and 

 absorption of intraocular fluid, and subsequent results cannot be compared 

 with those obtained before such a cessation of circulation. The raising of the 

 intraocular pressure in itself may act as a stimulus and cause reflexly 

 alterations in blood flow, in the general blood pressure, or in the state of 

 contraction of the pupil. The co-operation of these various factors suffices to 

 explain the varying results obtained in the very many experiments we 

 performed upon this subject, including those of which we have already given 

 details. We are of opinion, therefore, that the results obtained by 

 Niesnamoff must be regarded as accidental, and that a greater number of 

 experiments would have convinced this observer of the fallacies of his method. 



