NEUROSECRETION. XI. THE EFFECTS OF NERVE SECTION ON THE INTERCEREBRALIS-CARDIACUM-ALLATUM SYSTEM OF THE INSECT LEUCOPHAEA MADERAE

¹ Department of Anatomy, University of Colorado School of Medicine, Denver, Colorado

1. The interpretation of the intercerebralis-cardiacum-allatum system of insects as a functionally related group of neuroglandular organs, in which the corpus cardiacum serves as a reservoir for neurosecretory material, is supported by the results of severance of the nervi corporis cardiaci. The insect, Leucophaea maderae, in which the components of this organ system are paired is favorable for the study of these relationships since one side can be left intact and compared with the operated side.

2. Following the interruption of the neurosecretory pathway at the level where the nervus corporis cardiaci enters the corpus cardiacum, the distribution of the neurosecretory material changes markedly in comparison with the normal situation. Proximal to the site of nerve section there is an accumulation, and distal to it there is a drastic depletion of neurosecretory material. This result offers conclusive evidence that in the intact system the neurosecretory substance originating in cells of the pars intercerebralis of the brain is transported via their axons (forming the nervi corporis cardiaci) to the corpora cardiaca where it is stored. This interpretation of the morphological situation makes it understandable that no physiological indication of hormone deficiency was observed as a consequence of the nerve transection (B. Scharrer, 1946a).

3. Severance of the nervi corporis cardiaci also results in histological changes in the corpora allata. The organs become larger and seem to contain more cytoplasm than normal glands. Their nuclei are more vesicular and the nucleoli more distinct. These changes do not indicate an organ deficiency, since "severed" corpora allata of Leucophaea are functionally equal to, or perhaps even more competent than, normally innervated glands.