THE ANTERIOR LYMPHATICS OF THE EYE. 341 



The latter is also completely filled by the injection. In many 

 preparations, injected vessels may also be observed in the 

 sclerotic, which run from the canal of Schlemm, backwards 

 and outwards through the fibrous membrane. Careful observa- 

 tion shows that these vessels are indubitably veins. Never- 

 theless, the canal of Schlemm must still be regarded as a lymph 

 space, since the characters of its walls are essentially different 

 from those of a vein. It communicates with the anterior 

 chamber of the eye by means of a system of fine fissures. 

 These fissures occur between the elastic ircular fibres and 

 fenestrated membranes, which extend from the margin of the 

 membrane of Descemet, and form a modified prolongation of 

 this membrane as far as to the posterior point of insertion 

 of the ciliary muscle, and are continuous internally with the 

 trabecular ineshwork of the canal of Fontana. This peculiar 

 tissue bridges over a groove situated on the inside of the 

 anterior border of the sclerotic, where it joins the cornea, and 

 converts this groove into a lacuniform circular canal, which 

 is, in fact, the canal of Schlemm. The ciliary plexus of Leber 

 is situated, as he himself states," in the compact tissue of the 

 sclerotic, just external to this groove. 



In many cases, instead of one patent orifice, there are two or 

 more, and thus a transition is effected to the eyes of Mammals, 

 in which several small lumina are present at the same point, 

 but which are always placed internally to the groove of the 

 sclerotic. 



The manner in which the canal of Schlemm is connected with 

 the veins in its vicinity is still unknown. In all probability 

 certain valvular arrangements exist, which prevent the pas- 

 sage of venous blood into the canal of Schlemm, under the 

 normal conditions of pressure. If we consider what the con- 

 sequences would be if the anterior chamber of the eye were 

 to have in the lymphatics its proper discharge pipes,, we 

 shall readily understand the meaning of the above-described 



* Anatomische Untersuchungen iiber die Blutgefdsse des menschlichen 

 Auges. (Anatomical researches upon the bloodvessels of the eye of Man.) 

 Denkschriften der Kaiserlichen Akad.. der Wissenschaften zu Wien. Math,- 

 Naturwissensch. Classe^ Band xxiv., p. 316. 



