ORGANS OF THE BODY. 



647 



it, giving the reactions neither entirely of albumen nor of glutinous bodies, 

 but exhibiting properties to some degree intermediate between the two. 



319. 



Before passing on from the globe of the eye, we must bestow a few 

 words upon its lymphatic vessels. 



From Schwalbe's investigations it would appear that the lymph formed 

 in the ball of the eye is carried off in three directions. That produced in 

 the iris and ciliary processes is collected, in the first place, in the anterior 

 chamber. This with the absorbents of the conjunctiva and corneal 

 tissue may be said to belong to the first part, or anterior lymphatic circula- 

 tion of the eye. 



All the lymphatic spaces situated behind the ciliary processes empty 

 their contents in two other directions. Those of the sclerotic and choroid 

 open near the points of exit of the venae vorticosse, while the absorbents 

 of the retina, on the other hand, are independent of these, and leave the 

 globe of the eye through the optic nerve. Here, then, we have what we 

 may call a posterior lymphatic circulation. 



Let us consider this posterior lymphatic circulation first (fig. 600). 

 Both the sclerotic and choroid seem destitute of special lymphatic vessels. 

 Instead of these the shell-like interspace between the two coats appears 

 to possess the nature of a lymph receptacle. This occupies the position of 

 the supra-choroidea, as is well known ( 310). To this receptacle, which 

 is crossed by connective-tissue net- 

 works, the name of " pericho- 

 roidal space " (p) has been given by 

 Schwalbe, who describes it as lined 

 by endothelium. From this (at 

 about the height of m.r. in our 

 figure) that communication with 

 " Tenon's space " (t) takes place 

 which has been already alluded to. 

 The latter lies between Tenon's 

 sheath and the external surface of the 

 sclerotic. The oblique intercom- 

 municating canals invest, as a rule, 

 the venae vorticosae like sheaths. 

 This lymphatic space of Tenon is 

 continuous behind with the "supra- 

 vaginal" (spv) of Schwalbe, which 

 latter invests the external optic 

 nerve sheath "like a sheath." In 

 it, also, there is apparently a lin- 

 ing of endothelial cells. 



By Key and Retzius it was found 

 ( 300), that from the subdural 

 space of the cranium another space 

 between the external and internal 

 sheath of the optic nerve may be 

 injected, and that from this the 

 perichoroidal interval may be filled, which would seem to show that the 

 latter is a prolongation of the first. Between the internal sheath and 

 the connective-tissue immediately investing the optic nerve fibres, injection 

 42 



Fig. 600. Posterior lymphatic circulation in the 

 eye of a pig (diagram after Schwalbe). e, con- 

 junctiva; m.r. recti muscles; m. retr. retractor 

 bulbi ; a, layer of fat; v, external sheath of optic 

 nerve; t, "'Tenon's" space opening behind into 

 the "supravaginal" tpv; sbv, "subvaginal" 

 space between the internal and external optic 

 nerve sheath; p, "perichoroidal" space com- 

 municating by oblique passages with Tenon's 

 space. 



