[Ultrastructure of the hyaloid canal and its retraction during gestation (author's transl)].

1. The cells of the hyaloid canal originate from the primitive meningeal cells; 2. The lumen of the hyaloid canal can be observed through the optic nerve up to the subarachnoid space around the optic nerve; 3. Injections of tracer substances into the subarachnoid space of the optic nerve have shown that a communication between the subarachnoidal space and the lumen of the hyaloid canal is formed up to the capsula of the lens during the first 14 weeks of gestation. It may be assumed that in vivo cerebrospinal fluid reaches the lens because of the hyperplastic differentiation of the choroid plexus in the sixth week of gestation; 4. The distal two-thirds of the hyaloid canal retract between the 17th and 22nd week of gestation; 5. From the beginning of the 22nd week of gestation there exists an open communication between the subarachnoid space and the corpus vitreum.