Certain Histological and Anatomical Features of the Central Nervous System of a Large Indian Spider,Poecilotheria

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Abstract
SYNOPSIS. Some of the finer details of the anatomical organization of the subesophageal ganglion of the spider, Poecilotheria sp. were studied in Palmgren silver-stained sections at the light microscopic level. The ganglionic mass is differentiated into a central fibrous core and a peripheral layered mass of cellular cortex. The neuropile is heterogeneous, consisting of both diffuse and glomerular types, and is considered the primary place for integration. The dorsal region is motor, and the ventral is sensory. The processes of motor cells and endings of sensory neurons are restricted mostly to a single ganglion. Each large motor neuron possesses a long stem-process, short and highly branched dendritic ramifications, and a smooth, unbranched axon. Larger interneurons are more diversified, and extend from one to several ganglia. These are of ascending or descending or even decussating types. Smaller interneurons are mostly restricted to one or a few ganglia. On the basis of this organization the probable synaptic junctions between neurons are discussed.