The writers examined by means of the Limulus test 130 samples of cerebrospinal fluid and eighteen samples of serum obtained from subjects affected by extremely varied neurological conditions as well as by lumbar and sciatic pain of disc origin. They demonstrated that the Limulus test was positive in cases of lumbar and sciatic pain in which clinical, myelographic and surgical findings gave positive results. It is therefore probable that there is correlation between positivity of the test and an auto-immune pathogenesis of root pain in disc hernia.