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Histological procedures are necessary in brain stimulation or lesion work to determine the neural area which has been stimulated or damaged. Preparation of brain tissue often involves embedding and staining techniques that require specialized training, and the expense of a technician and a large assortment of special apparatus and supplies. In addition, the results of such techniques are unavailable for at least several days. A photographic method, which requires little special skill and a minimal amount of apparatus, is described here. Results can be available within minutes after the subject is sacrificed. This method has been shown to be adequate for the gross determination of lesion boundaries and electrode or cannula tip loci in brains of rats, cats, and squirrel monkeys.

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Rats were conditioned to avoid shock on a free‐operant avoidance schedule in which no exteroceptive stimulus signaled impending shock. Injections of adrenocorticotropic hormone (ACTH) or dexamethasone raised blood levels of glucocorticoids. These increases were accompanied by changes in avoidance performance: there was a higher frequency of long‐duration interresponse times, a greater stability among them, and fewer short interresponse times, total responses, and shocks.

This timer was designed to provide a compact and quiet unit to control the presentation of visual stimuli by means of a slide projector, but it is not limited to this use. It is a solid state device, ready for use as soon as switched on, and is made largely from commercial logic units. The output is in the form of contact closures: the ON relay and the OFF relay give short pulse closures at the beginning of their respective cycles. With circuit values as shown in Fig. 1, times, from 0.5 to 10 sec in increments of 0.5 sec with an accuracy of ±1%, are selected by separate switches on the ON and the OFF cycles. Single interval solid state timers have been described by Saslow and Markowitz (1964) and by Tapp and Clark (1964).

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In behavioral studies it is often necessary to classify events and store the number of events occurring in each classification. The classification requirements may be either functions of amplitude (i.e., intensity, force, peaks, etc.) or time (i.e., duration, interval, etc.). The following describes an analyzer capable of classifying events according to their duration, interval, or time of occurrence, and storing and displaying the number of such events in each classification.

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A swivel was developed for concurrent intraorganismic fluid injection and intracranial electrical stimulation of the unrestrained rat. Effects of various intragastric injections on bar‐pressing maintained by electrical stimulation of the hypothalamus were studied. In some subjects, intragastric injections of either water or milk decreased the rate of responding. This decrease resulted from pauses in responding rather than from decreases in the local rates of responding. The decrement in responding occurred at a lower gastric volume during milk injection than during water injection. In other subjects, however, neither water, milk, nor 32% sucrose injections affected the rate of self‐stimulation.