A toxiphobia conditioning paradigm was used to examine the relation between the intertrial interval (ITI) and the extinction of an aversion. The design employed was based upon that developed by Davis (1970) to study the relation between the ITI and the habituation of a response. After conditioning, the conditioned stimulus (CS) was presented on two occasions at times T1 and T2, and this interval (the ITI) was varied across groups. However, the interval from the CS exposure at T2 to the extinction test was common for all groups. On the test, ITIs of 6 to 24 hr were found to have promoted more extinction than ITIs of 0.5 hr with odour (Experiments 1a and b) and flavour (Experiment 1c) CSs. Further, this facilitation of extinction by the long ITIs compared to the short ones was not due to differences in the intervals between the initial CS exposure at T1 and the test (Experiment 2). The final experiment examined the relation between the ITI and extinction when different CSs were presented at T1 and T2. A short interval between the presentation of CS1 at T1 and the presentation of CS2 at T2 was found to have facilitated the extinction of the aversion to CS2 compared either to a long interval between these presentations or to the presentation of CS2 in the absence of a prior CS1 presentation. The results were discussed in terms of the model developed by Wagner (1981).

The prevalence of abdominal abnormalities depicted at US in AIDS patients has increased since 1983.

Evidence is set forth to show the value of continuous long-term anticoagulant therapy by comparison with a control group of patients who have also had multiple coronary occlusions or single infarcts, followed by severe angina pectoris or episodes of coronary failure. Statistical life-estimate determinations are included. Bleeding complications are encountered less frequently with improved methods of management and are considered a justifiable risk, in view of the serious consequences of the natural progress of the disease. After a program of long-term anticoagulant treatment has been instituted, cessation of therapy may be hazardous.

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