Abstract
1. The carotid body of Urolocha domestica was studied by light and electron microscopy.
2. The ultrastructure of the chief cell essentially corresponded to that of the mammalian carotid body.
3. Many nerve terminals occurred around a chief cell, some of which made synaptic contacts with the latter. The synaptic vesicles were on the neural side as in the mammalian carotid body, and it was considered that these nerve terminals were of efferent nature.
4. Synaptic contacts were described between nerve terminals themselves around the chief cell. The synaptic vesicles occurred frequenty on both sides of this axo-axonic synapse. In this type of synapse accumulations of synaptic vesicles may not necessarily indicate a presynaptic nature.
5. Synapse between a chief cell and a nerve terminal having further synaptic contracts with other terminals was illustrated and discussed. This type of synapse was similar to the so-called serial synapse regarded by some authors as a possible morphological basis for presynaptic inhibition.
