338 THE LYMPHATICS OF THE EYE, BY G. SCHWALBE. 



vascular canals of the same nature as those demonstrated by 

 the same author in the brain and spinal cord. The veins and 

 capillaries are completely invested by these lymphatic sheaths, 

 whilst the arteries are probably only surrounded by them 

 through a definite portion of their course. The injection of 

 the retinal lymphatics may be accomplished by driving the 

 fluid with considerable force into the bloodvessels. The latter 

 give way at certain points, and the fluid then escapes through 

 the rents into the perivascular canals. The discharge of the 

 retinal lymph takes place in the optic nerve through the lamina 

 cribrosa. According to His, the outer portion of the optic 

 nerve contains a rich plexus of lymphatics, which, however, 

 are here no longer perivascular. 



A cavity which was described by Henle and Merkel (9), and 

 which is situated between the membrana limitans interna and 

 the optic-fibre layer of the retina, probably communicates with 

 the perivascular canals of the retina. Lymph corpuscles are 

 found in this position, but no injection of it has hitherto been 

 successfully made. 



The relation of the tissue of the vitreous to the lymphatic 

 system is still unknown. Stilling (11) found that in the eye 

 of the Pig a central vessel, perforating the vitreous from .be- 

 hind forwards, could easily be shown by dropping a solution of 

 carmine upon the posterior surface of the latter, and this he re- 

 garded as a lymphatic canaL The perivascular canals of the 

 hyaloid of the Frog, described by v. Iwanoff (10), are the ana- 

 logues of the perivascular canals of the retina of Mammals. 



c. A lymphatic cavity which does not communicate with 

 either of the two systems just described is found between the 

 two optic sheaths throughout their whole extent from the bulb 

 to the canalis opticus. On account of its position beneath the 

 fibrous sheaths of the optic nerves, it may be termed the sub- 

 vaginal cavity (fig. 369, sbv). It opens directly into the 

 arachnoidal space. At the point of entrance of the optic nerve 

 into the globe of the eye it extends to close beneath the 

 choroid, though without entering into communication with the 

 perichoroidal space. Its walls are lined by an endothelium, 

 which is very easily separable in the form of small nucleated 

 scales. The space is traversed by a rich plexus of delicate 



