Cysts in rabbit foetal brains. Malformation or artefacts?

Reports have appeared in the literature on brain cysts in rabbit foetuses. This paper reports on investigations carried out to assess whether "cystic dilatation" is a malformation or an artefact. The results show that "cystic dilatation" arises by splitting of the pia-arachnoid membrane leading to a space between the skull and the neural tissue which is lined by the pial layer on its interior aspect and the arachnoid on its exterior aspect. The evidence presented indicates that "cystic dilatation" is a fixation-induced artefact. In addition, the presence of several artificial tissue clefts and spaces in preserved rabbit foetal brains is reported.