Pearson ( '28) repoi-ted a slight decrease in vihrtttorp sensibility in persons over 30 years of age, which, as he said, becomes particularly striking after the age of 50. I'eai*son believed that "the most probable locatioii for the pathologic changes underlying this decrease is the posterior coliimns of the spinal Hc stated that the lesion was probahlp vascular. Using what they believe to be a more exact and more objective method of determining vibratory acuity, Semman and Corbin ('36) found a similar climinution in this sensibility with age.
Duncan ('30) reported the presence of less tlian 174 of degcneratiiig fibers in normal nerves of the rat, rabbit, cat and man. He recently ( '34) determined the number of fibers in the ventral roots of the r a t at different ages. He found a decrease in the number of ventral root fibers in the old rats, u p to one-tenth of thc total number at 800 days. H e concluded that the degenerating fibers, observed in normal nerves a t all ages, are not replaced as claimed by Agduhr ( '20).
TTTe have made this study to determine the source of the d e c w a s e d periplicral sensibility, with age. We realize that our series is not large but believe the resiilts are significant enough to marrant this report.
Methods
In most cases the nerve roots were rcinovecl from human bodies used for dissection. These bodies had been embalmed 6.7