The subcommissural organ of submammalian vertebrates: a histochemical study.

Since morphological data do not allow to draw conclusions concerning the phyletic evolution of the subcommissural organ (SCO), a "metabolic" criterion is considered. Histoenzymology permits a comparison of metabolic activity in the subcommissural organ and that found within the ependyma. During the course of phyletic evolution, one notes various changes. Indeed, in lower vertebrates, the SCO presents a greater degree of enzyme activity than the ependyma while in birds the ependyma demonstrates a more intense activity than the SCO. The results are also compared with those previously reported in reptiles and mammals. In all vertebrates, glucid catabolism seems predominent in this areas.