Phase Contrast Microscopic Observations on the Posterior Pituitary of Dog, with Special Reference to the Difference between the Neurosecretory Substance in the Hypothalamic Neurosecretory Nucleus and in the Posterior Lobe

Abstract

The posterior pituitary of normal dog was observed by phase contrast microscopy, and the following results were obtained:1. Many granules are observed in the so-called ‘Verdichtungszone’ of the posterior pituitary esp. perivascularly. These granules are identified with the neurosecretory granules because of a close resemblance of their size, shape and distribution to those of gomoriphil granules in the fixed and stained section after GOMORI's method.2. No like granules are observed in the cytoplasm of a pituicyte.3. These findings are about the same in a fresh section as in a fixed section other than with alcohol.4. By the phase contrast method, neurosecretory granules are not observed, in the section fixed with alcohol, in hypothalamic nucleus, but they are observed in the posterior lobe. This result has nothing to do with re-fixation or no re-fixation of the section with ZENKER's or BOUIN's fluid. It leads us to the conclusion that there is a difference of chemical nature esp. of the conditions of combination with lipid between the neurosecretory substance in hypothalamic neurosecretory nucleus and that in the posterior lobe.