The tracheal supply to the central nervous system of the locust

Abstract

The tracheal supply to the central nervous system of the locust has been revealed by staining with cobalt sulphide. Air that enters through the first pair of thoracic spiracles is carried first to the brain and then to the rest of the central nervous system. The air is expelled through the abdominal spiracles, so that there is a one-way circulation with diffusional exchange only in the blindly ending tracheae that enter the brain or ganglia. Once inside a ganglion, the tracheae branch profusely to end in a mass of fine tracheoles through which gaseous exchange takes place. The densest tracheation is in the neuropile areas, where the spacing between tracheoles is about 17 μm. In the optic lobes, where there is order to the synaptic arrangement of a neuropile, there is a matching orderliness of the tracheation. Cortical areas, which contain the cell bodies of neurons, have only a sparse tracheation. It may be concluded that it is the processes associated with synaptic transmission that require the most immediate access to the sites of gaseous exchange.