A number of experiments of the type suggested by Piaget & Inhelder's book La genèse des structures logiques élémentaires were given to a population of primary and educationally subnormal (E.S.N.) special school children. The findings among the former group generally confirm those of the Geneva school. It has been possible to extend Piaget & Inhelder's findings by giving a number of tests to the same children, and by making a comparative study of primary and E.S.N. school pupils.

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The Order Statistic model of reliability growth offers improved • experimental design, and • flexibility in testing methodology compared to conventional reliability growth models. It permits prediction of operational reliability without requiring that testing be conducted according to the operation profile of the program input space.This paper presents the first experimental use of the Order Statistic model under a test plan that combines both representative and directed tests. Results suggest that this is an effective way to obtain quantified measures of test quality without abandoning the advantages of directed test methods.

SIR,-T-cell chronic lymphocytic leukaemia (T-CCL) is rare inEurope and the U.S.A., accounting for only 2% of all CLL cases. I Malignancy of mature T-cells is more frequent in Japan, where this disorder is usually referred to as adult T-cell leukaemia (ATL).2 2 Serum antibodies against the structural core protein (p24) of a human C-type leukaemia virus (human T-cell leukaemia-lymphoma virus or HTLV) have been demonstrated in Japanese patients with ATL, suggesting a possible viral aetiology. Catovsky et a1. 4 have reported a series of Black patients of West Indian origin with malignancy of mature T cells virtually indistinguishable from Japanese ATL and high titre antibodies against HTLV.Evidence that HTLV-positive T leukaemia is not confined to Japan prompted us to look for anti-HTLV antibodies in ten patients from Italy with T-CLL; eight of these patients have been described elsewhere. ],5,6 All patients were born in Italy and they live (or lived) in the Rome metropolitan area or in Padua. Slight hypercalcaemia (a feature of ATL) was observed in patient K while under chemotherapy. Nuclear convolutions, but not pleomorphism,2 were noted in cells from patients J and K who had skin infiltration. Cells from patients G, H, J, and K displayed the immunological pattern (T3+,T4+,T8-) recorded by Japanese workers for adult T-cell 653-60 9 Aisenberg AC, Wilkes BM, Harris NL, et al Chronic T-cell lymphocytosis with neutropenia Report of a case studied with monoclonal antibodies Blood 1981; 58: 818-22. 10 Rumke HC, Miedema F, Ten Berge IJM, et al. Functional properties of T cells in patients with chronic T gamma lymphocytosis and chronic T cell neoplasia J Immunol 1982; 129: 419-26.

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