Caliber spectra of fibers in the fasciculus gracilis of the cat cervical spinal cord: a quantitative electron microscopic study.

In order to obtain a better understanding of the microscopic structure of the cat fasciculus gracilis, entire cross-sections of the fasciculus were examined with the electron microscope. Twenty-five thousand, two hundred and eighty-four fibers were encountered in one fasciculus. The fiber caliber spectra obtained from the study show that the fasciculus gracilis at cervical level has a unique fiber distribution pattern. The fiber diameters range from less than 1 mu to 15 mu, however, 97 percent of fibers have diameters less than 8 mu; and the majority of the fibers are in the 2-5 mu range.