421 



here a necessary consequence of the tension (20inni. to 

 30mm.) of the liquid in the anterior chamber, which would 

 cause it to escape were it in communication with vessels in 

 which the tension is so low as it is in lymphatics, instead of 

 with veins. In seeking for the channel of communication 

 between the chamber and the veins, Schwalbe was led to 

 study the structures situated in the angle between the poste- 

 rior surface of the cornea and the anterior surface of the iris, 

 namely, the ligamentum pectinatum and the canal of Schlemm 

 (sinus vel circulus venosus Iridis). The ligamentum pecti- 

 natum is regarded as corresponding to the so-called canal or 

 space of Fontana in the lower animals. Under these names 

 is understood a trabecular network occupying the groove of 

 the sclerotic which corresponds to the insertion of the ciliary 

 muscle. The laminae of this structure are a direct continua- 

 tion of the substance of tlie membrane of Descemet (mem- 

 brane of Demours, posterior elastic lamina), and are covered 

 with endothelial sheaths, which are continuous with the 

 endothelium covering that membrane. They are further 

 continuous with the endothelium on the anterior surfiice of 

 the iris, and thus the endothelial lining of the anterior cham- 

 ber is complete. The canal or sinus of Schlemm is in most 

 animals only represented by one or two of the interstices of 

 the ligamentum pectinatum which are larger than the rest, 

 but in man it is a more distinct cavity. Its inner wall is 

 formed by a continuation of the membrane of Descemet, 

 Avhich ceases to be a hyaline membrane, and breaks up a 

 fenestrated structure, the openings of which correspond with 

 the lamina? of the trabecular tissue of the ligamentum pecti- 

 natum, while its outer wall is formed by dense tissue which 

 is continuous with the sclerotica. It is lined by an endothe- 

 lium containing few nuclei, but in this respect the endothe- 

 lium of the membrane of Descemet often resembles it. It is 

 through the fenestrated structure, between the laminte of the 

 ligamentum pectinatum, and through the canal of Schlemm that 

 an injection passes from the anterior chamber to reach the veins 

 above spoken of. A network of minute veins (the ciliary plexus 

 discovered by I^eber) permeates tliese structures, but the veins 

 are perfectly distinguishable in vertical sections, and the canal 

 of Schlemm itself is, according to Schwalbe, distinctly a 

 lymphatic and not a venous space. Standing, as it does, 

 in communication with veins on the one side, and with the 

 anterior chamber on the other, it may be filled from either of 

 these ; but an injection from the anterior chamber enters it 

 under very slight pressure (without filling the ciliary plexus) , 

 while an injection from the venous system can only be made 

 to enter it by using very considerable pressure. If an in- 



