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



II. The Effect of Changes in the Circulation on the Formation of Intraocular 



Fluid. 



If the production of intraocular fluid is dependent on a process of filtra- 

 tion through the blood vessels and the epithelium covering the ciliary 

 processes, its rate must vary directly with the difference of pressure on the 

 two sides of the filtering membrane. It must vary, therefore, directly with 

 changes in the capillary blood pressure, and inversely with the changes in 

 the intraocular pressure. In our first series of experiments we sought to 

 eliminate the second factor, namely, that of absorption, by opening the 

 anterior chamber, so that the intraocular pressure could be regarded as zero. 

 A cannula was introduced into the anterior chamber and the fluid allowed 

 to flow off into weighed porcelain capsules. These were changed every 

 10 or 20 minutes, and the amount of fluid secreted in the time determined 

 by weighing. The fluid drained off during the first minute after insertion of 

 the cannula was regarded as normal intraocular fluid, but the gradual 

 emptying of the eye-ball continues during the first five minutes, so that the 

 figures obtained during this time cannot be regarded as expressing the rate 

 of secretion. In every case the total solids of the intraocular fluid were also 

 determined. 



The following experiment, p. 298, shows the results obtained while the blood 

 pressure was approximately constant. It will be seen that there is a constant 

 diminution in the amount of fluid obtained. In these experiments we were 

 at first troubled by the formation in the anterior chamber of clots, which 

 tended to plug the cannula. We found that this difficulty could be obviated 

 by the injection of a dose of leech extract, not large enough to cause a 

 permanent diminution of the blood pressure.* 



The next question to determine was whether it was possible to alter the 

 rate of production or the composition of the intraocular fluid by altering the 

 blood pressure in the vessels of the eye-ball. The experiments on this point 

 were all carried out on dogs. A diminution of the intraocular blood pressure 

 was easily effected by ligature or obstruction of the carotid artery on the same 

 side. In order to produce a maximal rise of pressure in the blood-vessels of 

 one eye, the vertebral and subclavian arteries on both sides were tied. 

 A loose ligature was placed round the thoracic aorta, so as to permit of its 

 being obstructed at any given time. A cannula connected to the mercurial 

 manometer was placed in the carotid artery on the right side. The production 

 of intraocular fluid was determined in the left eye. By obstruction of the 



* This procedure had been previously employed by Mr. E. Pfliiger in some experiments 

 carried out in this laboratory in 1902. An account of these experiments will shortly 

 appear as a dissertation in the University of Bern. 



