Vascularization of the optic pathway. III. Study of intra-orbital and intracranial optic nerve by serial sections.

Technique The tissues to be studied were preferably taken from patients who had died of congestive heart failure, the blood being pressed towards the regions under study. All the surrounding large vessels were ligated and afterwards the optic nerve was dissected over its whole length from the orbital, intracanalicular, and intracranial contents. The technique employed was that of Pickworth (1934), as modified by Fazio and Farina (1940). The tissue, after irrigation, is wrapped in hydrophilic gauze and immersed from 3 to 5 days in a fixative of saturated sodium chloride (15 ml.), saturated glucose (15 ml.), and formol 10 per cent. (5 ml.). Frozen sections are then cut of approximately 50,. thickness and treated as follows: A sodium nitro-prussate solution, 0 * 5 per cent. (20 parts) is mixed with 25 parts of a 0 5 per cent. benzidine solution; the latter, containing 2 per cent. acetic acid, gives a cloudy precipitate. After filtration, 80 parts aq. dist. are added to the filtrate. The sections are immersed in this preparation for 20 to 30 minutes at 37°C. After irrigation by tap-water they are immersed for a further 10 minutes at 37°C. in oxygen water (12 vol.), rinsed in tap-water, and treated with absolute alcohol (to dehydration). Thereafter they are ready to be examined microscopically. In order to see the small capillaries it is advisable to cover the preparation with Canada balsam.