Innervation of the carotid body, types of nerve endings and their possible significance.

The nerve endings in the carotid body of normal cats are investigated by means of serial sections. Two types of endings not described previously are especially studied: the non-synaptic bouton and the meniscus with prolongations. The first is a small nerve ending with abundant mitochondria and glycogen which is devoid of synaptic vesicles. The second is a normal meniscus which presents prolongations containing the same cytological elements of the nonsynaptic boutons. It is proposed that some menisci are lateral endings of an afferent fiber. Relating these results with well-known functional characteristics of the carotid body, the existence of axonal reflexes is suggested. These views can explain apparently contradictory facts.