Morphology and distribution of muscle spindles in dorsal muscles of the cat neck.

Silver-stained sections have been examined from the five dorsal neck muscles splenius, biventer, cervicis, complexus, rectus capitis major, and occipitoscapularis. Every serial section was examined for at least one muscle of each type so that a complete description of the spindle distribution and morphology could be made. With the exception of occipitoscapularis (whose prime function is probably in scapula rotation and not in head movement), neck muscles have a remarkably high spindle density. Occipitoscapularis has a spindle density similar to that of hindleg locomotor muscles (13-19 per gram), but splenius has a density of 46-66 per gram, biventer cervicis 74-96 per gram, complexus 71-107 per gram, and rectus capitis major 48-84 per gram. Such high densities have only previously been seen in small muscles whose total spindle population is not large. Because of the relatively large size of some neck muscles, individual muscles with a spindle content of up to 254 spindles have been found.