The postnatal development of the efferent projections to the lumbosacral spinal cord from the brain stem of rats were studied with HRP retrograde transport method. Fifty per cent solution of HRP was slowly injected into the intumescentia lumbalis on its right side in 18 albino rats from postnatal 1-35 days. The HRP labelled cells were found in the following nuclei:1. Of the midbrain: the nucleus ruber, substantia nigra and nucleus raphe dorsalis.2. Of the pons: the nucleus reticularis pontis oralis, nucleus reticularis pontis caudalis, locus coeruleus, nucleus subcoeruleus, nucleus raphe magnus, nucleus vestibularis lateralis, and nucleus vestibularis medialis.3. Of the medulla oblongata: the nucleus raphe obscurus, nucleus raphe pallidus, nucleus reticularis ventralis, nucleus reticularis gigantocellularis, nucleus reticularis lateralis, nucleus tractus spinalis nervi trigemini, nucleus commissuralis (Cajal), nucleus prepositus hypoglossi, and nucleus gracilis.The number of the labelled cells in the above nuclei increased steadily with age. The results of present study showed that there was a postnatal developmental process in the efferent projections from the brain stem to the lumbosacral cord. The maturity of the projections from ruber nucleus and locus coeruleus were later than those of the vestibulospinal and reticulospinal tracts. The postnatal developmental process of the brain stem projections to the lumbosacral spinal cord were completed by one month after birth.

An intercostal nerve-spinal cord implantation and semitransection of the spinalcord at the point between the origin and insertion of the intercostal nerve was madeon ten adult dogs and two monkeys.One to two weeks after this operation,paraly-tic legs following semitransection of the spinal cord recoverded from the paralysis.The implanted nerves were cut during the different period from 124 to 366 days.The function of the legs of four animals which had recovered paralysed again aftersurgical section of implanted nerve.Histologically,the inserted nerves in the spinalcord were recognized in these animals.Many of the growing fibers extended fromdistal end of the inserted intercostal nerve into the gray and white matter ofthe distal segment of the spinal cord.It is considered that the efficacy of the inter-costal nerve-spinal cord implantation depends upon the choice of the symptomaticindications and the success of the implantation procedure.