William L. Straus

Rudimentary Digits in Primates

TH E Primates are among the most generalized of mammals in that they possess five well-developed digits on both manus and pes. While this is true of most members of the order, a few forms nevertheless depart from the ordinal rule. In these species, one or more digits normally are so under-developed that they must be regarded as stunted or even rudimentary. This condition usually is more than merely dimensional in nature, for, as will be shown, it commonly involves external characters, skeleton, and musculature. Such type of stunted digit, normal for a given species, falls into a different category from those anomalous rudiments that occasionally occur in man and other primates as well (see Schultz, 1942). The latter do not lie within the scope of this paper.

An Unfortunate Event

After Dement and Kleitman (1) first described a low-voltage, fast electroencephalographic sleep cycle in humans, the same type of activity was described in cats by Dement (2) and later by Jouvet et al. (3). We have duplicated this desynchronized sleep electroencephalogram in five of our cats that have been implanted with bipolar electrodes in various deep and surface structures of the brain. These animals have been trained to go to sleep in a sound-proofed room. Behavioral and electroencephalographic arousal thresholds in response to stimulation of the reticular formation are then recorded. The cats exhibited the normal behavioral and electroencephalographic patterns associated with going to sleep, and after 60 or more minutes of complete isolation they drifted into a very high frequency (40 to 50 per second), low amplitude, desynchronized activity (Fig. iB). As described by Jouvet et al. (3), the animals were completely relaxed and deeply asleep. Especially noticeable are the occasional convulsive limb twitches. One of the cats slept with the eyes partially open during this phase. She showed marked nystagmic movements of the eyeball under relaxed nictitating membranes. Although Dement (4) states that he cannot detect changes in arousal threshold between the fastor slow-wave sleep stages, we have found increases in the reticular formation behavioral arousal thresholds of from 1 to 2.5 volts in all of our cats (Fig. 1). This finding confirms Jouvets report (3) of increased auditory and reticular arousal thresholds during this sleep period. One aspect of this desynchronized sleep stage not yet reported is shown in Fig. 1C. Recticular stimulation that

Cranial capacity of Oreopithecus bambolii.

From a plaster reconstruction of the skull of the August 1958 skeleton, the cranial capacity of Oreopithecus bambolii has been estimated as fallingbetween 276 and 529 cubic centimeters, thus within the ranges of variation of both orangutan and chimpanzee. In cranial capacity, therefore, and probably in body-brain ratio as well, Oreopithecus is a hominoid.

Age of Zinjanthropus: The potassium-argon dates recently obtained from Olduvai Gorge, Tanganyika, raise several questions.

Because some of the Olduvai Gorge dates are inconsistent, some must be inaccurate; they may all be. Until further tests determine which materials give dependable dates, we do not know which dates are accurate. Until this is learned, the indicated ages must be taken cum grano salis.