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.1 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 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 pregnancy 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. still if we consider the weight of the mated females just at the end of the period of gestation (before partuition), or better if we add the weight of the young, immediately after birth to that of the mother, we shall find that the weight of the breeding female is in the ratio of 1. 164:1 to that of the male. The relationship after parturition (not adding the weight of the young to that of the mother) is 0.848:1. HENSEN in an Anhang to EDLEFSEN's work, made some observations upon a litter of 4 guinea pigs, 3 females and 1 male, in order to determine the relationships between the growth of unmated females and males and thus supplement the results of EDLEFSEN. To control his results he mated one of the females. The following table presents his conclusions: The weight of the mother just before parturition was 612 grammes. In this table we find some slight ground for inferring that the males grow at least as rapidly as the unmated females. On the other hand, the figures point to the fact that breeding females, reckoning in the weight of their young, actually build up more bodily material, than either the unmated females or males during a corresponding period of growth. HENSEN then tried to determine the total increase in weight of one mated female during the period of gestation, apart from the increase in weight of her young. He began his reckoning at the time pregnancy first became noticeable. This happened on the 28th day after conception. The female weighed 335 gr. at this age. In the remaining 39 days of pregnancy (28 + 39 days period of gestation) she herself gained 100 gr. in weight and produced 146 gr. of bodily substances in young and adnexa, i.e. 1.46 times more than she herself gained. MINOT tabulated the average changes in the weights of 66 female guinea pigs, from the beginning of the period of gesta tion to parturition, and then again for 35 days immediately after parturition. The usual length of the period of gestation is from 67 to 68 days. The average weight of the 66 pregnant guinea pigs just before delivery was 830.2 gr. Their average weight 3 days after delivery was 588 gr. The average weight of unmated females at that age, he had previously determined from many observations to be 532.1 gr. Thus it appears that at the end of pregnancy, the breeding females were heavier than those not allowed to breed, by about 55.9 gr. MINOT'S tables presenting the average alterations of weight of these 66 guinea pigs from the 35 days immediately after the delivery of their young, show that there is a very great loss of weight, especially marked during the earlier days of this period. Subsequently there is a slower loss in weight continuing for about three weeks, after which recovery begins. Owing to the destruction of MINOT's pigs-the story of which has become classic in the annals of American research— further investigation of this subject was cut short. If we compare the results of EDLEFSEN and HENSEN's observations on the growth of gestating guinea pigs during their first pregnancy, with those of MINOT, we find a contradiction. EDLEFSEN and HENSEN conclude that the growth of the gestating females, when considered apart from the young developing in them, is slower than that of either the unmated females or males. MINOT, on the contrary, concludes that the mated females immediately after partuition are heavier than the corresponding unmated females by 55.9 gr. On account of the large number of animals with which MINOT worked, his results are probably the more reliable. Observations upon the Body-weight of the White Rat. The writer's observations were begun upon a series of rats in the spring of 1903 and were continued for approximately one year. The females under observation were selected from five litters of rats born in April and May of that year. The |