Hydrostatic pressure under the skin of sharks varies with swimming speed. Stress in the skin varies with the internal pressure, and the skin stress controls skin stiffness. Locomotory muscles attach to the skin which is thus a whole-body exotendon whose mechanical advantage in transmitting muscular contraction is greater than that of the endoskeleton.

Abstract-Unusually high extensibility of the kelp Nereocystis Zuetkeana minimizes tain high stresses (force per cross-sectional breakage by waves and tidal currents. Cellu-

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The results of this study may be used by educators and employers to develop and structure learning experiences and mentoring opportunities for students and novice learners with the aim of facilitating the development of skills and abilities consistent with expert clinical decision making.

We describe the complex shapes of myomeres and myosepta in the mackerels and tunas (Scombridae: Teleostei), and we reveal the orientation of two major systems of collagen fibers in myosepta and horizontal septa with respect to points of attachment to skeleton and skin. Our goal is to identify the likely pathways of the transmission of muscle forces during locomotion. Our primary conclusions are (1) that the collagen fibers of myosepta, horizontal septa, and skin are the organs that transfer locomotor forces from the contraction of myomeres to the backbone and caudal fin during locomotion, and (2) that locomotor muscle pulls against a three-dimensional structure of tendons, septa, and skin that is kept in tension by the radial expansion of the contracting muscle. The main horizontal septum is formed by the convergence of myosepta and is likely to be the major transmitter of muscle force to the axial skeleton. The geometry of the myomeres, the position of red muscle, and particularly the geometric conformation of crossed-fiber arrays of collagen in the main horizontal septum suggest specific mechanisms for the transfer of muscle force to the backbone among scombrid fishes. Morphometrics and the construction of physical models help us to identify musculoskeletal mechanisms of locomotion, and we present two quantitative models of locomotor mechanics in fishes. © 1993 Wiley-Liss, Inc.

SYNOPSIS The Camberwell Psychiatric Register was searched for contacts by the 2257 women resident in the register catchment area who were known to have had a child in 1970. Of these, 99 women (and 39 of their husbands) were found to have had a 'new episode' of psychiatric illness in the two years before or the two years after the birth of their child. The distribution of these 'new episodes'relative to the time of childbirth was then studied. In the women, both functional psychoses and depressive illnesses showed a sharp rise in the new episode rate in the three months immediately after delivery. There was also a suggestion of a secondary rise, less dramatic but more sustained, from the 10th to the 24th month after delivery. There was no comparable rise in the husbands. Women whose children were illegitimate had high new episode rates throughout the four-year study period, but not particularly so in the puerperium itself.At one time puerperal psychosis was believed to be a distinct condition with a symptomatology, psychopathology and prognosis different from those of other psychoses. The failure to find any sexual differences between women with puerperal psychoses and other psychotic women (Anderson, 1933) and the demonstration that both the clinical features and the prognosis of puerperal illnesses were much the same as those of other functional psychoses (Strecker & Ebaugh, 1926;Vislie, 1956;Foundeur et al, 1957) discredited this belief. As a result, interest in the concept waned, and contemporary glossaries discourage use of the term (American Psychiatric Association, 1968;General Register Office, 1968). Nonetheless, there is good evidence that childbirth is followed by a sharp rise in the incidence of functional psychoses. Pugh et al. (1963), for example, studied admissions of women of childbearing age to public mental hospitals in Massachusetts, and found that, although the admission rate was below expectation throughout pregnancy, it rose to several times the expected rate in the first three months after delivery. As this rise was too large to be

The results of this study may be used by educators and employers to develop and structure learning experiences and mentoring opportunities to facilitate clinical decision-making abilities and the development of the skills necessary for reflection in students and novice practitioners.

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