This first part of this paper is a review of the literature on the functional anatomy of the sacroiliac joint followed by a preliminary biomechanical study of the fresh post mortem pelvis. The latter was done in order to determine the coefficients of the screw matrix and the position of the instantaneous centers of rotation during the symmetrical movements of nutation and contranutation simulated in the biomechanics laboratory. The main part of this work deals with the spatial analysis in vivo of the relative displacements of the iliac bones with respect to the sacrum in the course of dissymmetrical movements of the pelvis. In the different phases of movement, the roentgenographic observation of the position of the bony components with respect to a three-dimensional orthonormal reference system required the use of material based on the principles of photogrammetry. This technique was used to achieve spatial reconstruction of the data recovered from a series of orthogonal x-ray films of the sacroiliac joints. Data retrieval was carried out on a digital table linked to a computer with a graphic terminal so that the information could be displayed in the form of rectangular coordinates of defined points on the bone. Owing to the limited amplitude of articular displacement, a statistical study was required to retrieve the coordinates from the projection of these points on the X-ray film with an estimated threshold of significance of 0.1 and an error of +/- 0.1 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

-This paper investigates the within-and between-tree variability of hardness and basic density in two stands of 11-year-old and 20-year-old maritime pine trees grown in the south-west of France. A slight increase was found in the inner core hardness of the 11-year-old trees (+13.9 %) and in basic density of the 20-year-old pines (6.5 %) with decreasing tree height. Between the 1st and 13th annual rings of the 20-year-old trees, hardness increased by +49.8 % and basic density by +18.7 % on average. These variations were strongly tree-dependent. A significant correlation was found between hardness and basic density, even when each sampling position was considered independently. (

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