Fresh brain gives good result, the blood has to be drained out first using normal saline. The latex to be injected should be diluted with distilled water to make it free flowing while injecting ( Diluted latex can also easily enter the capillaries) . To prevent latex from escaping when needle is withdrawn a drop of Potassium Alum (saturated aqueous solution) can be applied or if large vessels it can be clamped. Placing the specimen in formalin will harden the latex. The Latex solution to be used should be stirred as within few minutes of preparation the rubber particles may rise to the top. latex becomes tough flexible rubber like when injected in specimens embalmed or preserved in formalin. I have done this procedure some 10 years back , hope it will help you. All the best

Injection via carotid and/ or vertebral arteries; pressure 100 mm HG constanst. LAtex may be colored with different colors to show distribution. for red color menninge (lead-tetroxide) is an excelletnt option, since this is also radio-opak to produce artreriographs. all the pretreatment (saline solution etc.) is not necessary or rather a disadvantage. to keep the shape of the brain either use a barin-shaped (calvaria shaped) rreceptable to hold the brang onin or suspend rhe brain ha