NEUROSECRETION

Abstract

Groups of nerve cells which pass through secretory cycles in the manner of gland cells occur in the C. N. S. of invertebrates and vertebrates. They are found, for instance, in the pars intercerebralis of the insect brain, in the nucleus preopticus of the fishes and amphibians, and in its homologues, the nuclei supraopticus and paraventricularis, of the reptiles and mammals. In fishes and amphibians the secretory granules of nerve cells appear to originate in association with basophil constituents of the cells, i.e., chromatin, basophil cytoplasm, or Nissl bodies. In insects and fishes the products of neurosecretory cells can be observed along the axons to glands of internal secretion. Attempts to interpret the function of such cells by correlating their intercellular secreting cycles with seasonal cycles in the lives of the animals have failed, though correlation is found in some species. However, in 2 instances in invertebrates the origin of physiologically active substances has been traced to parts of the C. N. S. which contain neurosecretory cells. One of the substances causes molting in Rhodnius (Hemiptera). The other, obtained from worms, molluscs, and arthropods, has a chromatophorotropic action.