Erdheim [1931] and Hirsch and Schajowicz [1953] have pointed out that the annulus fibrosus joins the vertebral bone by means of a preparatory calcareous layer. This point of view has not gained wide acceptance. Most authors dealing with the structure of the intervertebral disc describe the attachment of the annulus fibrosus as occurring through Sharpey’s fibers [Niednek, 1932; Policard, 1942; Coventry et al., 1945; Schmorl and Junghanns, 1968; Galante, 1969; Fried, 1970]. We therefore decided to reinvestigate how the annulus fibrosus and the longitudinal ligaments are inserted into the vertebral body. Material and methods

Human lumbar segments of different ages were removed post mortem. Particular care was taken not to injure the perivertebral ligaments. There were 3 male and 3 female subjects, aged 0, 9, 16, 22, 22 and 34 years. The causes of death were stillbirth, traffic accident (2 cases), congenital and acquired heart disease, and acute myelogenous leucaemia. After freezing at-20¤ C, pairs of 0.5 cm thick sagittal, coronal or horizontal slabs were isolated with a slowly rotating saw. One of each pair of slabs was demineralized and embedded in paraffin, while the other was left undecalcified and put into methylmethacrylate to be X-rayed and eventually stained. The material was fixed in a 10% aqueous solution of formaline. Decalci-fication was carried out with equal parts of 8 N formic acid and 1 N sodium formate. The solution was renewed daily. Demineralization was regarded as complete when a Sulkowitch test, performed on the supernatant, proved to be negative. HE and Masson’s green trichrome stain were used systematically; selected sections were stained with Alcian blue or Bodian’s protargol. The undecalcified bone fragments were embedded in methylmethacrylate (Union Chimique Beige) after dehydration with methanol and defatting with chloroform and toluol. The pieces were sawed into slices 125–175 µm thick with a GH 1 thin-sectioning machine (Hamco, Roch-1 This investigation was supported by a grant of the ‘Comité de Concertation des Activités scientifiques du Ministère de la Defense nationale’and of the ‘Fonds national de la Recherche scientifique’.