INTRACRANIAL AND INTRAOCULAR FLUIDS I 76/ 



fig. 7. Oblique section of the 

 human ciliary body. [From Wolff 

 (253)-] 



— — - */.* rom> 



Ascher's belief that they represent visible channels 

 for drainage of the aqueous humor, and the circum- 

 stance that their presence may be repeatedly de- 

 tected in the same place in the same subject indicates 

 that drainage is a continuous process, i.e. that the 

 aqueous humor, like the cerebrospinal fluid, is con- 

 stantly being renewed. 



We may thus picture the circulation of the aqueous 

 humor as a primary elaboration of the fluid in the 

 posterior chamber by the epithelium of the ciliary 

 body, associated with a flow over the lens and through 

 the pupil into the anterior chamber where it perco- 

 lates through the trabecular meshwork in the angle 

 and across the endothelial lining of Schlemm's 

 canal. From Schlemm's canal the fluid empties into 



veins to become blue. Klcinert (135) has contributed useful 

 information on the ramifications of the aqueous veins, while 

 Ashton (8, 9) has actually dissected them out from neoprene 

 casts of the canal of Schlemm. Useful reviews of this subject are 

 those of VVeinstein (245) and Ascher (7), their value in the 

 experimental approach to glaucoma is indicated in Goldmann's 

 comprehensive study (ill). 



the venous system; some of the aqueous humor may 

 travel in aqueous veins to reach the superficial epi- 

 scleral and conjunctival veins, while the remainder 

 is carried by short collectors which empty at once 

 into the veins of the intrascleral plexus. On this view, 

 then, the main regions of interchange between blood 

 and aqueous humor arc in the ciliary processes and 

 in the angle of the anterior chamber. The aqueous 

 humor is in close contact with another vascular tis- 

 sue, namely the iris, and it is reasonable to expect 

 that exchange of material between blood and this 

 fluid will take place here, the more so since in main 

 species, including man, the anterior surface is not 

 covered by any very well defined endothelial layer 

 (229, 254) so that the aqueous humor may apparentlv 

 percolate between the connective tissue cells of the 

 anterior lamina to come into direct relationship 

 with the capillary circulation. The actual role of the 

 iris in the formation or absorption of the aqueous 

 humor has been a matter of controversy; since colored 

 substances, injected into the anterior chamber, ap- 

 pear in the anterior ciliary veins, and not the vortex 



