308 Mr. E. E. Henderson and Prof. E. H. Starling. [Nov. 23, 

 Inflow three minutes later at same intraocular pressures — 



Salt. Serum. 



6 3 



5 3-5 ; 



5 6 



' 5 4 



' ' ' 4 4 



Fifteen minutes later — 



3-5 1-5 



3-0 1-5 



3-5 1-5 



etc. etc. 



This difference in the rate of filtration of the two fluids becomes greater 

 the higher the intraocular pressure is raised. 



VI. TJic Effect of the Size of the Pupil on the Absorption of Intraocular 



Fluid, 



In the experiments we made to decide this point, one eye of the animal 

 under observation was treated with eserine and the other with atropine. 

 The instillation of these drugs should be begun before the induction of 

 anaesthesia, as the action of eserine is very uncertain if only instilled after 

 anaesthesia. 



We have found, as a result of these experiments, that the intraocular 

 pressure in the two eyes remains the same during the time of observation, 

 but that, if the pressure in the apparatus be raised, the rate of filtration in 

 the eye under eserine is much greater than in that under atropine. 



It is difficult to give a precise explanation as to the cause of this difference. 

 Stretching of the filtration spaces at the angle of the anterior chamber may 

 possibly account for it all. If this, however, is the case, we should expect to 

 find the intraocular pressure at a lower level in the eye with the contracted 

 pupil, for the intraocular pressure must of course be the product of the rate 

 of secretion and the rate of absorption of the intraocular fluid. The same 

 objection applies to the explanation of this phenomenon by Gronholm (9), who 

 states that in his opinion it is due to diminished intraocular secretion as a 

 result of the contraction of the intraocular vessels. It may also be possible 

 that at these raised pressures other channels of filtration are opened up — 

 such for instance as the surface of the iris. An important, perhaps the most 

 important, factor, however, must be the crushing of the dilated flaccid iris 



