SIGHT

The experiments on sight bear simply on such rays as we ourselves are able to perceive, and were performed in a carefully constructed and thoroughly efficient photographic dark room. From the subjective standpoint, the animals were allowed to swim in the dark, but whether what we call dark is in reality dark to a rat, is another question.

Two sets of animals were used, two adults, and two young ones less than a year old. Each animal was given four sets of six trials. The averages follow:

If the first two series of A are compared with the last two, it will be found that this animal remained practically constant in speed; if a similar comparison be made for B, we find that this individual increased its speed on the average by 9.28"; whereas the records of a and b show increases in efficiency in each of the last three sets. Undoubtedly, then, the tank problem can

be solved in the dark, and the solution, may with repetition, become a habit, but the evidence does not show that the sense of sight plays no part under other circumstances. Watson's negative evidence on this point seems very good, but the maze problem and the tank problem differ so much, that what is true in the solution of the one, is not of necessity true in the solution of the other.

TOUCH

Touch in the ordinary sense, is practically eliminated by the nature of the problem. The actual solution takes place in a medium in which the animals float. There are no solid bodies to be touched; no differences in homogenity in any direction, that might guide the individuals to the correct opening. . The same thing applies to the temperature sense. It is possible, however, that touch and temperature, singly or together, affect the result, but if they do, it is not in the usual way, but as the initiating stimuli of other activities.

THE KINÆSTHETIC CHAIN

With hearing, smell, sight and touch, either eliminated, or shown to be not essential, the question of how the habit becomes established, naturally arises, Watson ('07) and others have presented a large body of evidence suggesting that the kinæsthetic sense may be the controlling factor in the behavior of the white rat. My own experiments seem to bear similar interpretation, but if the facts corroborated by the tank method are due to a kinæsthetic sense, it follows that this needs investigation.

Granted that a relation exists between the objective phenomena which we call a habit, and the inferred basal kinæsthesia, the inference that the relation is definite, seems just; for the habit itself is definite, and capable not only of exact measurement, but also of modification. It follows that in the emergence of a habit, the internal basis also is modified, for the habit itself is modified behavior. In other words, kinæsthesia is easier to understand if

thought of as a sequence of states which will be repeated, provided the physiological state of the animal remains favorable, whenever the stimuli that started it in the first place recur.

It is here that any sensations associated with the beginning of a solution may come into play. Unfortunately, I have no results to offer on this subject at present, but the standpoint itself may not be without value. If kinæsthesia is indeed a special element in the sum total of internal conditions, is in fact a chain, based on the physiological, and expressed objectively in the habit, the answer to a difficult problem may be a little easier to find than heretofore.

SUMMARY AND CONCLUSIONS

My purposes in presenting these results have been to show the adequacy of the tank as an instrument for studying animal behavior; to show that our usual methods leave out of consideration a large range of interesting activities; and finally to demonstrate that behavior, limited to brief periods of very intense exertion under stress, may lead to the formation of habits.

Incidentally, the results seem to corroborate, as far as they go, some of the conclusions set forth in Watson's splendid work, and wherever at variance, are so probably from the differences between the problem of the maze, and the problem of the tank. In certain ways, the latter seems well suited for studying the "direction sense" or whatever it is that in the absence of sight, hearing, smell, and touch, enables the animals, not only to solve the problem, but to improve in efficiency. If kinæsthesia plays an important role, if indeed it is by this means that the animals sense direction, and if furthermore, it is a sequence of states, dependent on the physiological condition of the animal, and on certain initiating stimuli, then by variations in the last two categories, one should get changes in kinesthesia, which in turn would be registered by corresponding differences in the objective habit.

Accepted by The Wistar Institute of Anatomy and Biology, March 18, 1910. Printed July 7, 1910.

BIBLIOGRAPHY

WATSON, JOHN B. Animal Education. The University of Chicago Contributions 1903 to Philosophy, vol. 4, no. 2.

WATSON, JOHN B. Kinæsthetic and Organic Sensations, etc. Psychological Review, Monograph Supplements, vol. 8.

1907

Zoological Laboratory, University of Michigan.

January 13th, 1910.

ON THE MEDIAN ANTERIOR CEREBRAL ARTERY AS

FOUND AMONG THE INSANE

I. W. BLACKBURN

From the Government Hospital for the Insane, Washington, D. C.

WITH SIX FIGURES

The subject of anomalies of the cerebral arteries among the insane has received considerable attention in the past, especially noteworthy being the article by Bullen in the Journal of Mental Science, volume 36, 1890,1 but unfortunately comparative statistics are meagre. In 1907 I made a study of the conditions of development of the encephalic arteries in 220 consecutive cases of mental diseases, making a comparison with the studies of Windle? in 200 cases of those presumably sane. The results of this comparison seemed to show a decided predominance, in general, of anomalous conditions among the mentally diseased.

3

In the study above mentioned, being chiefly concerned with the anomalies of the circle of Willis, sufficiently careful studies of other arteries were not made, and as a result, the anomalous vessel which forms the subject of this paper was not as frequently found as subsequent observations show is probably the fact. This artery is found of course among the sane as well as the insane. My studies, however, are based upon the examination of 400 consecutive cases of mental disease examined with special reference to this vessel. In all of the text books of anatomy at my com

'BULLEN. Post mortem Examination of the Brain, etc. Journal of Mental Science, vol. 36, 1890.

2 WINDLE. On the Circle of Willis. Reports of the British Medical Association, for 1887. New York Medical Journal, vol. 2, 1888, and Journal of Anatomy and Psysiology, 1887-1888.

'BLACKBURN. Anomalies of the Encephalic Arteries among the Insane. Journal of Comparative Neurology and Psychology, vol. 17, no. 6, 1907.