sing Karnovsky’s histochemical method

the different parts of the superior laryngeal nerve(SLM) loop from 12 dogs after immediate sacrifice

including communicating branch between su-perior cervical sympathetic ganglion and external laryngeal nerve branch and several segments ofthe mixed trunks

were examined for their acetvlcholinsterase activities to distingush the fibercomponents of the SLN loop

The specimens were fixed with 6% formalin (PH7)for 1h

imbed-ded in gelatin

cut into 7μm slices

mounted in glasses

incubated in the medium prepared accord-ing to Karnovsky and Roots

direction for 24 hrs

and then observed under the light microscope.The results showed that the communicating branch contained mainly unmylinated fiberswhich showed strong enzymatic activity . the mixed nerve trunks consisted of myelinated axons

some of which showed enzamatic activity and others failed to react

and unmyelinated fiberswhich showed strong enzamatic activity. These results demonstrated that the SLN loop is com-posed of motor

sensory nerve fibers and sympathetic postganglion nerve fibers.Therefore

SLNloop is a mixed nerve instead of a motor nerve.