The number and distribution of muscle spindles in human intrinsic postvertebral muscles.

Serial transverse sections of intrinsic postvertebral muscles of a 21 weeks old human fetus were studied after staining with haematoxylin and eosin, Van Gieson's stain with Weigert's haematoxylin, and Glees' silver impregnation technique. Muscle spindles have been demonstrated throughout the entire length of the intrinsic postvertebral muscles. The total numbers of spindles on the right and left sides were determined. Using a special technique of graphic reconstruction, the locations of spindles within these muscles were plotted. Regional differences in the numbers and distribution of spindles were noted. The significance of these findings has been discussed.