Showing the average size of litters for the earlier portion of the breeding period AUTHORS Crampe ('84) King and Stotsenburg ('15) Long and Evans ('22) NUMBER 26 BIOLOGY age, pure and simple, or depends on the bearing of previous litters has not been determined.In extracted Albinos and in Norways the litter size is close to that for the stock Albinos, while in extracted Norways and in Piebalds it is somewhat higher: 6.7 and 6.8 respectively (King, '24).Greenman and Duhring ('23) find however in their exercised and particularly well fed series, breeding at four months, the first htter to be the largest. This is possibly another instance of precocity which may be thus induced, or it may be the result of the later age at which the female bred. Mortality.From a study covering five years and based on the litters from 415 rats. King ('21) determined that 1.3 per cent of the young were still born. The still born males were markedly in excess of the females (129 males to 100 females') due apparently to a greater intrinsic weakness of the male fetus. Young are also lost during the early days of lactation, through injury or neglect.Only a small number are born dead in the case of normal mothers. Where abnormal conditions exist, the number of dead born may be high.Birth weight. The birth weights as determined by King ('15) are shown in table 7 according to the increasing age of the mother and in table 8 according to the increasing body weight of the mother.On the average the birth weight of the males exceeds by 0.3 grams that of the females.King ('15) reaches the following conclusions: Increasing age or increasing weight of the mother (the two being correlated) give a heavier birth weight, while the increase in the number in a litter tends to diminish the individual birth weight. There is to be observed also a diminution in birth weight in those litters born of mothers below the standard size, or suffering from infectious disease.Precise data for the birth weight require great care to secure the selection of young which have not suckled. This is most readily made by the use of the so-called obstetrical cage, de-scribed by Long and Evans ('22), by which the young are automat-ACTIVITY^-EXERCISE . 31Sounds. The sounds made by the rat range from an intimate chicking used by mothers with young to small squeaks in response to slight discomfort-rising to a high pitched scream when suffering severe pain or in great terror. Broadly speaking this last response comes most often from the wild Norways just after capture. Under experime7ital conditions. See References.Activity and exercise. When fed at midday Albinos divide the 24 hours into about 14 hours of interrupted rest and sleep and 10 hours of marked activity-from the early evening to the early morning (Szymanski, '18 a).They are as responsive to training during the period of inactivity as during the active period (Szymanski, '18).As incentives to learning, hunger, pain, and sometimes the maternal instinct (return to the young) are effective (Szymanski, '18 b).Richt...
F r o m the Nrurolofical Lnborafory of the Unavrrsitr~ of Chicago.) With one figure.1 The Acrania and Cyclostomi do not develop medullary sheaths on their nerve fibers, and are therefore not included.
IN the course of an investigation undertaken with. Pro! G. Stanley Hall and under his direction, it was incidentally observed that the sensation of cold was felt only at definite spots on the skin. The fact was noticed in this way: The sensations of motion as derived from the skin were being studied by means of a metal point which was slowly drawn over the surface. When the motion of this point, which was controlled by a suitable apparatus, was very slow, it often happened that it seemed to stand still for a time or even be lost, when suddenly a sharp sensation of cold, distinctly localised, would recall its presence and position. This occurred so often that I find in my protocol for April 18th, 1884, the note: "Point always felt as cold". This fact arrested my attention, and in connexion with the other work I made several maps of these cold-spots on different parts of the body. When the experiments had reached this point, an important paper by Magnus Blix (I) 1 came into my hands. This investigator started from the law of the specific energies of nerves, and took up the study of the dermal sensations to determine, if possible, how well-founded was the contradiction which they apparently offered to this law. He employed unipolar electrical stimulation, using a pin for his small electrode, and made use of an induction-current so weak that it did not generally cause pain. He thus produced at one spot on the skin a sensation of pain, at another pressure, at a third cold, and at a fourth heat. These spots were distinctly localised, and never superposed on one another. He gave special attention to the spots from which sensations of temperature were to be obtained. These he studied by means of a small metal tube drawn out to a conical point (Pig. TTT , below), and so arranged that a current of water could be kept flowing through it, thus enabling the observer to maintain the point at an approximately constant temperature. Using this instrument, he investigated various parts of the akin, and mapped out the heat-spots and cold-spots in several regions. Further, he applied the crucial test: a heat-spot and a cold-spot having been found, the warmed point was applied to both, then the cold. No sensation followed the application of the warmed
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