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A simple mathematical neuron model which is based on commonly accepted approximations and is designed for economical digital computer implementation is described. The model's properties are compared with those of real neurons and other more sophisticated models described in the literature. The simulation of two small networks which have been proposed as fundamental neural structures in the generation of the flight motor control stimuli in some insects using this model is shown to yield results which are superior to those of previously published simulations.

Some apparatus and instrumentation have been developed for improving the relevance of dynamic test data obtained from human muscle specimens. In the first part of this paper the background is given and a special clamping and mounting arrangement is described which allows a small specimen to be made ready for test in less than a minute. The second part describes a new timing and sequencing instrument for regulating the electrical and mechanical stimulations applied to the specimen. The mechanical displacements are controlled by a type of servomechanism which can be driven from an f.m. tape recorder.

Electromyographic studies on the reflex activity of the external anal sphincter were carried out in 42 patients with lesions of the spinal cord. All cases, with the exception of one (tabes dorsalis), were complete lesions at various levels of the cord. The external anal sphincter was found to show continuous tonic contraction at rest which depends on the integrity of the sacral segments and their peripheral outflow. Factors eliciting reflex excitation and inhibition resulting in increased contraction or relaxation of the tone of the external anal sphincter are described in detail. In particular the effects of increased intra-abdominal pressure, skin stimulation and distension of the anal canal and rectum are reported. The reflex mechanism of defaecation is discussed in the light of the management of bowel function in paraplegia.

The muscles of the pelvic floor are unique by virtue of their nervous mechanism. No other muscle will fulfill their function, which is the reason for failure of the Wredon-Stone operation for incontinence. Without constant reflex postural activity, there cannot be continence. The electrical activity occurring in the muscles of the pelvic floor, which can be recorded by electromyographic means, has been well described by other investigators. Our efforts have been directed toward investigation of the mechanism of this activity and the means by which it can be modified. Our findings suggest that the mechanism is reflex and we propose that it be known as thepostural reflex of the pelvic floor. In addition, we have described inhibition of this reflex by rectal distention. This phenomenon is also due to a reflex arc and we suggest that it be calledthe rectal inhibitory reflex. These closely interrelated reflexes have many practical and theoretical implications, especially in relation to continence and rectal prolapse.

Chagas disease is a rare condition in patients anywhere but in Central and Latin America. This case is therefore reported because the patient was born in Britain and spent only a short time in an area where Chagas disease is endemic. It is believed that this patient is the first case of Chagas disease to be treated in Britain. Chagas disease causes a generalized degeneration of autonomic ganglia and usually presents as megaoesophagus or megacolon. The disease may also cause the heart to enlarge followed by cardiac failure.