Location and distribution of tracheosyringeal motorneuron somata in the fowl.

Injection of horseradish peroxidase solution (HRP) into the tracheosyringeal musculature and tongue of the domestic chick labeled their motorneuron somata in the medulla. Those of tracheosyringeal motor neurons occupied the caudal portions of the nucleus nervi hypoglossi (n. XII), whereas those for motor neurons supplying the tongue occupied the rostral part. The rostrocaudal representations of tracheolateralis, sternotrachealis, and ypsilotrachealis muscles were roughly mapped by the rostrocaudal distribution of labeled somata in n. XII. Except for sparse labeling found in the caudal part of the dorsal vagal nucleus of a few animals, no labeled cells were found outside of n. XII. Most tracheosyringeal injections labeled contralateral n. XII, but section of the contralateral tracheosyringeal nerve high on the neck prior to HRP injection abolished this labeling.