“…This is clearly shown by the fact that, 3 weeks after fornix-sectioning, plasma corticosterone levels follow the pattern seen in the sham-operated controls, i.e., they are low in the morning and elevated in the afternoon. If, in addition, one takes into account that, in the animals with complete deafferentation of the HTA or with a frontal cut behind the optic chiasm the diurnal variation in pituitary ACTH secretion is still blocked 4 weeks after surgery [HalAsz et al, 1967a, b], then it may be concluded that the critical neural input essential for the diurnal fluctuation in the release of CRF, and reaching the HTA from anterior direction, is not mediated by the fornix as was postulated by Moberg et al This, of course, does not mean that the fornix can be excluded as a possible route through which the hippocampus might modify, either directly or indirectly, the cyclic activity of the CRF-producing HTA. The only assumption that can be made is that this influence is probably not fundamental in nature or, at least, can very easily be replaced by other nervous structures.…”