Adaptation of certain histological techniques for in situ demonstration of the neuro-endocrine system of insects and other animals

Three techniques for staining the secretory neurones in sections were applied directly to the whole brain and/or intact organs of the neuro-endocrine system of certain insects, and the whole brain of various invertebrates and vertebrates. After minor changes in the original procedures, in situ staining was achieved in those components of the neuro-endocrine system that are known to contain the neurosecretory material. With the Victoria blue staining technique, the secretory neurones, the neurosecretory pathway, and the storage-and-release organ were stained satisfactorily in all the experimental animals, in such a way that observations could be made in whole mounts or suitably dissected portions of the bulk-stained preparations. With the aldehyde-fuchsin and aldehyde-thionin staining techniques, the somata and the proximal portion of the axon of the neurones and the storage-and-release organ were usually stained satisfactorily enough for purposes of observation in the invertebrate material only. On sectioning the bulk-stained components of the neuroendocrine system and mounting the sections, the sites known to contain the neurosecretory material were revealed promptly. On comparing the information derived from mounts of the bulk-stained preparations with that derived from sections of similar preparations, and also with that derived from routine histological procedure, no difference was detected.