given five stimulations daily with light of one color. The stimuli were given one minute apart. Three different intensities 1, 2 and 4, were used, one being employed each day. The different intensities were given in the following order: two, four, one, two, etc., and the trials were continued until records were secured of twenty five reactions to each of the three intensities. The results were then tabulated in two distinct groups. One shows the rise of breathing rate under the influence of each of the three intensities (Table IV), and the other indicates the effect of repetition of the same stimulus (Table V). In case of these tests the first respiration after the stimulus was used in calculating the reaction.

TABLE IV. RELATION OF INTENSITY TO REACTION.

to

The results expressed in Table IV are of a negative character (see last column). Whereas all four birds reacted more. three vigorously to intensity I than intensity 2, were more sensitive to intensity 4 than 2, and the final average showed the animals to be slightly more sensitive to the lowest intensity than to the highest. Results more satisfactory would probably have been secured from a larger

number of animals, or if the different intensities of the stimulus had been used on the same day. But the latter course would not have given opportunity for observing, at the same time, the influence of repetition.

It will be seen by Table V (last column) that there was a strong reaction to the first of the five stimulations, a less vigorous one to the second, and steadily increasing reponses thereafter (8.0, 3.7, 4.1, 5.7, 6.9). It is not surprising that the second

reaction was weaker than the first, since the animals were better prepared for the second stimulus. That there was an increased amount of reaction thereafter is probably to be accounted for, partially on the basis of summation of stimuli, and partially in view of the fact that the short illuminations may have

occasioned mental action, thus indirectly favoring quickened respiration. These stimuli are not comparable to the meaningless pistol shots before mentioned, to which as we saw, the breathing curve quickly became insensitive. They are rather to be classed, though not in themselves of a significant character, with the cage sounds (cooing flapping, etc.), which never lost their disturbing influence upon the respiration. For the short flashes of light probably gave the animal glimpses of its prison, increased desire to escape, etc., in a word, meanings, which involved heightened, rather than depressed, breathing activity, and worked directly against the dulling tendency of repetition."

It is to be noticed that the normal breathing rates of the four animals used in this series of tests were considerably lower than those for the same birds in the preceeding series. P's average normal rate diminished from 23.3 to 20.9; Q's, from 24.9 to 23.1; S's, from 29.5 to 27.6; and T's, from 29.8 to 27.4. This decrease was probably due to the animals' getting more and more accustomed to the general conditions of the experiment, and thus giving a less quickened, or disturbed, rate when attached in the nest and before being stimulated.

I.

The normal breathing curve in pigeons is very similar to that of the human subject, except that the rate is about twice as rapid. Respiration is sensitive to several kinds of stimulation, and shows various modifications, especially quickening, shallowing, deepening, pauses and irregularities of contour.

2. Mechanical jars, sounds, and, perhaps, odors, influence breathing profoundly, especially jars, often causing abrupt inhibitions and many irregularities.

3. Stimulation by light also disturbs the breathing, though

'MACDOUGALL, R. Physical Characteristic of Attention, Psychological Review, 3, 159-180, 1896.

BINET et COURTIER, Influence de la vie émotionnelle sur la coeur, la respiration, et la circulation capillaire, L'Année psychologique, 65-126, 1896.

much less than do mechanical stimuli. The reaction usually involves an immediate quickening of rate, varying with the color of the light, and occasionally diminutions of amplitude and minor irregularities of contour.

4. Since an agreement was found between the color pref erences and the increase in breathing rate caused by colored light, it would seem that agreeable feelings are accompanied by respiratory quickening (and perhaps by shallowing and irregularity).

5. Daily reactions of four birds to three intensities of light, one intensity per day, showed no direct relation between amount of stimulus and amount of reaction. The second daily reaction showed the influence of repetition, since considerably weaker than the first; but thereafter was seen a continuous increase in amount of response.

6. Meaningless stimuli, as pistol shots, quickly lose their disturbing influence upon respiration, although it remains sensitive to those of a significant character, such as noises made by other birds. A stimulus which no longer influences the breathing, will sometimes occasion disturbance if accompanied by a second stimulus, of another order, even though of weak intensity.

THE EFFECT OF THE BEARING OF YOUNG UPON

THE BODY-WEIGHT AND THE WEIGHT OF THE

CENTRAL NERVOUS SYSTEM OF THE FEMALE
WHITE RAT.

By JOHN B. WATSON.

(From the Neurological Laboratory of the University of Chicago.)

With Plate VI.

By observations in this laboratory the results of which are as yet unpublished', the normal increase in the body weight of the female white rat, uninfluenced by the bearing of young, has been determined. In this connection, a question arose as to the effect on the body growth, if the females were allowed to breed normally. The present paper reports the results of an investigation carried out in answer to this question. In addition to the above, there arose the further question, as to the effect of the bearing of young upon the weight of the central nervous system, and on the percentage of water contained in it.

So far as the writer knows, only three men have published observations bearing directly upon the subject in hand; viz., EDLEFSEN, HENSEN and MINOT.

EDLEFSEN recorded the changes in the weight of 7 female guinea pigs from birth to the end of their first pregnancy. Unfortunately he compared the weight of the females during preg. nancy with the weight of the males of a corresponding age. He made two points clear: Ist, the actual growth of the female guinea pig is slower during the period of gestation than that of the males of the same age during the same time; 2nd, that while the true body weight of the mother immediately after parturition is less than that of the male of corresponding age,

'It is expected that the results of this investigation will be published at an early date.