dequeueBodyCallback = function dequeueBodyCallback(name) {

        // If no callbacks defined, simply return null
        var callbacks = bodyCallbacks[name];
        if (!callbacks)
            return null;

        // Otherwise, pull off first callback, deleting the queue if empty
        var callback = callbacks.shift();
        if (callbacks.length === 0)
            delete bodyCallbacks[name];

        // Return found callback
        return callback;

    }
Removes and returns the callback at the head of the callback queue for
the stream having the given name. If no such callbacks exist, null is
returned.

@private
@param {String} name
    The name of the stream to retrieve a callback for.

@returns {Function}
    The next callback associated with the stream having the given name,
    or null if no such callback exists.