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The urinary bladder is assumed to be an incompressible isotropic material like a rubber. Then, by making use of the finite deformation theory for such a hyperelastic continuum, we have calculated the intravesical pressure and the mural stress of the bladder as a function of its volume. The formula for the mural stress contains two parameters. These parameters are determined by the uniaxial extension test of the dog bladder sample. The calculation result shows that the pressure is relatively flat while the stress continues to rise with the volume. This is the typical behavior in the normal living cystometrogram. From these analysis, therefore, we conclude that such a behavior comes from the elasticity of the bladder itself, and requires no explanation in terms of reflex inhibitory relaxation, urinary bladder; neurogenic bladder; urodynamics; an elastic body theory; cystometrogram A normal bladder holds its contents under very low pressure. Moreover, it holds increasing volumes of fluid with little increase or constant in intravesical pressure. This behavior seems to be quite strange, because the bladder-mural tension continues to increase with its volume whereas intravesical pressure remains constant. Why does not the pressure increase with the volume ?Traditionally this is explained in such a way that a network of nerves over the bladder wall plays a role of tension-controller who holds the pressure constant. On the other hand, Ruch (1965) has proposed in his text book another mechanism that the flat behavior of the pressure in a cystometrogram comes from an elasticity of the bladder itself, and requires no explanation in terms of reflex inhibitory relaxation. His theory is based on the law of Laplace, which holds for any elastic spherical body in the form p=2T /r, where p is the intravesical pressure, T the mural tension and r the radius of the spherical baldder. If T is proportional to r (Ruch called this Hook's law) in this equation, then it is clear that p remains constant. Thus, Ruch has persisted that it is unnecessary to postulate an active

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Mixed germ cell tumours of the ovary, one type of malignant ovarian germ cell tumours (MOGCTs), are rare gynaecologic cancers usually affecting young women. We report the case of a patient with an advanced ovarian mixed germ cell tumour who underwent fertility-saving surgery followed by a chemotherapy regimen of cisplatin, vinblastine and peplomycin. The patient was disease-free 8 years after initial presentation. She conceived and gestated dichorionic twins after IVF-embryo transfer. To the best of our knowledge, the patient is the first to be treated successfully with the combination chemotherapy regimen and then conceive safely using assisted reproductive technology (ART).

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