bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ACCELERATING EFFECT OF MANGANOUS IONS ON PHAGE ACTION
Authors: Krueger A. P. , West N. S.
Published: May 2004

Dilute solutions of MnCl2 or MnSO4 accelerate the lytic effect of phage upon susceptible staphylococci. Under the conditions of our experiments the manganese-containing mixtures lysed regularly 0.5 hour sooner than the controls.

The effect is shown to be due to a lowering of the lytic threshold, i.e. the quantity of phage/bacterium requisite for lysis; Mn++ reduces the ratio from 54 to about 12. In the presence of Mn++ phage distribution is altered and in growing phage-bacteria mixtures the extracellular phage concentration is increased by manganese to approximately 4 times that occurring in the absence of manganese. There appears to be no enhancement of phage formation nor any affect on the rate of bacterial growth. As would be anticipated, for any given initial phage concentration the end titre after completion of lysis is less in the presence of manganese than in its absence. This is due to the reduced lytic threshold produced by Mn++, there consequently being less phage needed to bring about lytic destruction of the bacteria.
THE MOLECULAR WEIGHT AND ISOELECTRIC POINT OF THYROGLOBULIN
Authors: Heidelberger Michael , Pedersen Kai O.
Published: May 2004

1. The sedimentation constant of hog thyroglobulin is 19.2ċ10–13. That of human thyroglobulin is essentially the same.

2. The specific volume of hog thyroglobulin is 0.72.

3. The isoelectric point of native hog thyroglobulin is at pH 4.58, that of denatured thyroglobulin at pH 5.0.

4. The molecular weight of hog thyroglobulin is, in round numbers, 700,000, as calculated from the sedimentation and diffusion constants, or 650,000, as calculated from the sedimentation equilibrium data.

5. The thyroglobulin molecule deviates markedly from the spherical.
THE DARK ADAPTATION OF THE EYE OF THE HONEY BEE
Authors: Wolf Ernst , Zerrahn-Wolf Gertrud
Published: May 2004

Bees which are held in a fixed position so that only head movements can be made, respond to a moving stripe system in their visual field by a characteristic motion of the antennae. This reflex can be used to measure the bee's state of photic adaptation. A curve describing the course of dark adaptation is obtained, which shows that the sensitivity of the light adapted bee's eye increases rapidly during the first few minutes in darkness, then more slowly until it reaches a maximum level after 25 to 30 minutes. The total increase in sensitivity is about 1000 fold.

The adaptive range of the human eye is about 10 times greater than for the bee's eye. The range covered by the bee's eye corresponds closely to the adapting range which is covered by the rods of the human eye.
THE VISUAL ACUITY OF THE FIDDLER-CRAB, UCA PUGNAX
Authors: Clark Leonard B.
Published: May 2004

The visual acuity of the fiddler-crab can be measured at various illuminations by means of its response to a moving visual pattern. The method, although similar to that used by Hecht and Wolf for the bee and Hecht and Wald for Drosophila, must be modified to give consistent results. An explanation of the response to a visual pattern is given in terms of the structure of the eye.

Visual acuity of the crab varies with log I as in man, the bee, and Drosophila. Hecht and Wolf's explanation of the varying visual acuity with illumination in terms of the distribution of functional ommatidia in the eye is supported to that extent.

In the fiddler-crab as in man, monocular and binocular visual acuity is similar with a maximum of 0.0042 for the fiddler-crab. This agrees fairly well with visual acuities of 0.0041, 0.0038, and 0.0032 as found in the field.

In man and the bee, the minimum visual angle corresponds to the minimum angle of two adjacent receptors; in Drosophila and the fiddler-crab the minimum visual angle corresponds to approximately twice the minimum angle between two adjacent receptors.
SULFHYDRYL AND DISULFIDE GROUPS OF PROTEINS
Authors: Mirsky A. E. , Anson M. L.
Published: May 2004

1. In native egg albumin no SH groups are detectable, whereas in completely coagulated albumin as many groups are detectable as are found in the hydrolyzed protein. In egg albumin partially coagulated by heat the soluble fraction contains no detectable groups, and the insoluble fraction contains the number found after hydrolysis.

2. In the reversal of denaturation of serum albumin, when insoluble protein regains its solubility, S-S groups which have been detectable in the denatured protein, disappear.

3. When egg albumin coagulates at an air-water interface, all the SH groups in the molecule become detectable.

4. In egg albumin coagulated by irradiation with ultraviolet light, the same number of SH groups are detectable as in albumin coagulated by a typical denaturing agent.

5. When serum albumin is denatured by urea, there is no evidence that S-S groups appear before the protein loses its solubility.

6. Protein denaturation is a definite chemical reaction: different quantitative methods agree in estimates of the extent of denaturation, and the same changes are observed in the protein when it is denatured by different agents. A protein molecule is either native or denatured. The denaturation of some proteins can be reversed.
THRESHOLD INTENSITY OF ILLUMINATION AND FLICKER FREQUENCY FOR THE EYE OF THE SUN-FISH
Authors: Wolf Ernst , Zerrahn-Wolf Gertrud
Published: May 2004

The sun-fish Lepomis responds to a moving system of stripes by a motion of its body. By changing the velocity of motion of the stripe system different flicker frequencies can be produced and thus the relation of flicker frequency to critical intensity of illumination can be studied. Threshold illumination varies with flicker frequency in such a way that with increasing flicker frequency the intensity of illumination must be increased to produce a threshold response in the fish.

The curve of critical illumination as a function of frequency is made up of two distinct parts. For an intensity range below 0.04 millilambert and flicker frequencies below 10 per second, the rods are in function. For higher intensities and flicker frequencies above 10, the cones come into play. The maximum frequency of flicker which can be perceived by the fish's eye is slightly above 50 per second.

The flicker curve for the eye of Lepomis can easily be compared with that for the human eye. The extent of the curve for the fish is greater at low illuminations, the fish being capable of distinguishing flicker at illuminations lower than can the human eye. The transition of rod vision to cone vision occurs for the fish and for the human eye at the same intensity and flicker frequency. The maximum frequency of flicker which can be perceived is for both about the same.
SULFHYDRYL AND DISULFIDE GROUPS OF PROTEINS
Authors: Mirsky A. E.
Published: May 2004

1. In the denatured proteins of skeletal muscle, the ratio of SH to S-S groups is higher than in the mixed denatured proteins of other tissues, with a single exception—the proteins of the crystalline lens.

2. The number of active SH groups in the proteins of minced muscle or in any of the protein fractions of muscle is only a fraction of the number found after the proteins have been treated with a denaturing agent.

3. The SH groups of the native proteins of muscle are activated by a rise in pH.

4. The relation between pH and number of active SH groups in the proteins of minced muscle and in the various protein fractions of muscle shows that little, if any, denatured protein is present in minced muscle.
ANOMALIES IN THE ABSORPTION SPECTRUM AND BLEACHING KINETICS OF VISUAL PURPLE
Authors: Chase Aurin M.
Published: May 2004

Visual purple from winter frogs shows an intermediate yellow color during bleaching by light; summer extractions do not. This seasonal effect can be duplicated by variations in the hydrogen ion concentration and in the temperature of the solutions. Increasing the pH approximates the summer condition, while decreasing the pH approximates the winter condition. Temperature has no effect on the bleaching of alkaline solutions but greatly influences acid solutions. At low temperatures the bleaching of add solutions resembles the winter condition, while at higher temperatures it resembles the summer condition.

A photic decomposition product of frog retinal extractions is an acid-base indicator: it is yellow in acid and colorless in alkaline solution. Its color is not dependent upon light.

The hydrogen ion concentration of visual purple solutions does not change under illumination, nor is there a difference in the pH of summer and winter extractions. Bile salt extractions of visual purple are usually slightly acid.

The conflicting results of past workers regarding the appearance of "visual yellow" may be due to seasonal variation with its differences in temperature, or to the presence of base in the extractions. It is also possible that vitamin A may be a factor in the seasonal variation.

The photic decomposition of visual purple in bile salts solution, extracted from summer frogs, follows the kinetics of a first order reaction. Visual purple from winter frogs does not conform to first order kinetics. Photic decomposition of alkaline, winter visual purple extractions also follows a first order equation. Acid, winter extractions appear to conform to a second order equation, but this is probably an artefact due to interference by the intermediate yellow.
ELECTRIC IMPEDANCE OF ARBACIA EGGS
Authors: Cole Kenneth S. , Cole Robert H.
Published: May 2004

The alternating current resistance and capacity of suspensions of unfertilized and fertilized eggs of Arbacia punctulata have been measured at frequencies from 103 to 1.64 x 107 cycles per second.

The unfertilized egg has a static plasma membrane capacity of 0.73 µf./cm.2 which is practically independent of frequency. The fertilized egg has a static membrane capacity of 3.1 µf./cm.2 at low frequencies which decreases to a value of 0.55 µf./cm.2 at high frequencies. The decrease follows closely the relaxation dispersion of the dielectric constant if the dissipation of such a system is ignored.

It is considered more probable that the effect is due to a fertilization membrane of 3.1 µf./cm.2 capacity lifted 1.5 µ. from the plasma membrane, the interspace having the conductivity of sea water.

The suspensions show a frequency-dependent capacity at low frequencies which may be attributable to surface conductance.

The equivalent low frequency internal specific resistance of both the unfertilized and fertilized egg is about 186 ohm cm. or about 6 times that of sea water, while the high frequency data extrapolate to a value of about 4 times sea water.

There is evidence at the highest frequencies that the current is penetrating the nucleus and other materials in the cytoplasm. If this effect were entirely due to the nucleus it would lead to a very approximate value of 0.1 µf./cm.2 for the capacity of the nuclear membrane. The measurements do not indicate any change in this effect on fertilization.
THE STRUCTURE OF THE ULTRAVIOLET ABSORPTION SPECTRA OF CERTAIN PROTEINS AND AMINO ACIDS
Authors: Coulter Calvin B. , Stone Florence M. , Kabat Elvin A.
Published: May 2004

1. The absorption spectra of a number of proteins in the region 2500 to 3000 A. have been found to comprise from six to nine narrow bands. In consequence of variation in the relative intensity of these bands from protein to protein, the absorption curve has a characteristic configuration for each protein.

2. These bands correspond closely in position with the narrow bands which appear in the absorption spectra of tryptophan, tyrosin, and phenylalanine. Tryptophan and tyrosin each present three bands, phenylalanine shows nine.

3. The bands in the proteins are accordingly attributed to these amino acids. In the proteins the bands are displaced from the positions which they occupy in the uncombined amino acids, in most instances, by 10 to 35 A. toward longer wavelengths.

4. The absorption spectrum of Pneumococcus Type I antibody resembles that of normal pseudoglobulin but shows characteristic differences.
THE BACTERICIDAL EFFECT OF ULTRAVIOLET RADIATION ON ESCHERICHIA COLI IN LIQUID SUSPENSIONS
Authors: Hollaender Alexander , Claus Walter D.
Published: May 2004

1. The irradiation of bacteria in liquid suspension has been made possible through: (a) the use of a specially balanced physiological salt solution which is practically non-absorbing for the wave lengths used, and which is of such composition that subsequent dilution of the bacterial suspension gives the proper number of organisms; (b) special design of the exposure cell and a very thorough method of stirring which subjects each organism equally to the radiation; (c) practically complete absorption of the incident radiation, through the use of very dense suspensions, thus eliminating the necessity for a separate determination of the absorption coefficients of the bacteria for the wave lengths used.

2. The method also provides a means for determining the effects of sub-lethal doses.

3. A formula is given for calculating from observed survival ratios the energy required to inactivate bacteria with ultraviolet radiation. The formula corrects for the protective action of non-viable organisms.

4. Data are given for the inactivation of 15 hour and 240 hour cultures of E. coli, washed and unwashed) and for 6–7 hour cultures, unwashed. These data are compared with those of other investigators.

5. A possible explanation for the differences in energy required to inactivate old, young, and standard cultures of bacteria is suggested.

6. The possible mechanism of the action of ultraviolet radiation on microorganisms is discussed.
THE SOLUBILITY OF d-VALINE IN WATER
Authors: Dalton John B. , Schmidt Carl L. A.
Published: May 2004

1. The solubility of d-valine in water has been determined over a range of 0–60°.

2. The solubility of this amino acid varies with the mode of crystallization, indicating a dependence of solubility on the crystal form.
PIGMENTS OF THE RETINA
Authors: Wald George
Published: May 2004

1. The interrelations of visual purple, retinene, and vitamin A in the bull frog retina are analyzed in simple experiments, the results of which are presented in a series of automatically recorded spectra.

2. Observations are reported upon the distributions, properties, and concentrations of xanthophyll, vitamin A, and flavine in the pigmented tissues of the eye.
ON THE INDIVIDUAL CHARACTERISTICS OF ANIMAL AMYLASES IN RELATION TO ENZYME SOURCE
Authors: Thompson William R. , Friedman Irving
Published: May 2004

Enzymes from various animal sources responsible for amylolytic activity as measured by a precise viscosimetric method have been investigated with regard to individual characteristics in relation to enzyme source. The principal criteria have been the course of spontaneous inactivation of preparations from different sources alone and in mixtures, and comparison of variations of relative activity with change in pH.

It is strongly indicated that the observed amylolytic activity of hog pancreatin, and that of the serum of a depancreatized dog are attributable to single chemical individuals, while that of human saliva is caused principally if not entirely by a single individual, which appears to be subject to reversible dissociation.

These three individuals are clearly distinguishable from each other.

The amylolytic activity of dog pancreatic extract is due to the same individual found in the serum of a depancreatized dog, while that of human pancreatic extract and of human serum are due to the same chemical individual found in human saliva. Thus it may be said of the amylases studied, that specificity depended upon species source rather than organ source.

Evidence of similar variations in activity with change in pH and equal sensitivity to ultraviolet light furnish strong indication that hog and human amylases have a common amylolytic radical.
ADAPTATION OF CUTANEOUS TACTILE RECEPTORS
Authors: Hoagland Hudson , Rubin Morton A.
Published: May 2004

Potassium is released from the epithelial cells of frog's skin on stimulation by an interrupted air jet. This evidence is consistent with the hypothesis that potassium is involved in the adaptation of the tactile nerve endings in frog's skin.
ADAPTATION OF CUTANEOUS TACTILE RECEPTORS
Authors: Hoagland Hudson
Published: May 2004

1. Both solutions of Ringer plus fifteen times the normal K content, and solutions of Ringer plus fifteen times the normal Ca content markedly hasten the adaptation of single freely branching axon endings in frog's skin to repetitive air puff stimuli.

2. The K effect is produced more rapidly than is that of Ca. The K effect is reversible by washing with Ringer's solution, while the Ca effect is not. The Ca inhibition can, however, be reversed and recovery effected by washing with K rich solutions.

3. Evidence is discussed which indicates that Ca probably plays no rôle in normal adaptation, and the experiments are interpreted as substantiating the hypothesis of adaptation due to K.
ELECTRIC IMPEDANCE OF INJURED AND SENSITIZED RED BLOOD CORPUSCLES
Authors: Curtis Howard J.
Published: May 2004

On the basis of previous work on the electrical properties of hemolyzed red cells, it might be supposed that the variation of the capacity with frequency at low frequencies is an indication of membrane permeability. To test this, rabbit red cells were subjected to treatment with lecithin, tannic acid, glucose, saponin, amboceptor, and colloidal silicic acid, each in sub-lytic doses. No change in any of the electrical properties of any of the suspensions could be detected. The result may mean that the form of the frequency variation is an extremely insensitive measure of permeability and other membrane changes, and capable only of disclosing the very great changes associated with hemolysis, or it may mean that the change in the frequency variation at low frequencies has nothing to do with permeability.
CHANGES OF APPARENT IONIC MOBILITIES IN PROTOPLASM
Authors: Osterhout W. J. V.
Published: May 2004

In normal cells of Valonia the order of the apparent mobilities of the ions in the non-aqueous protoplasmic surface is K > Cl > Na. After treatment with 0.01 M guaiacol (which does not injure the cell) the order becomes Na > Cl > K.

As it does not seem probable that such a reversal could occur with simple ions we may assume provisionally that in the protoplasmic surface we have to do with charged complexes of the type (KXI)+, (KXII)+, where XI and XII are elements or radicals, or with chemical compounds formed in the protoplasm.

When 0.01 M guaiacol is added to sea water or to 0.6 M NaCl (both at pH 6.4, where the concentration of the guaiacol ion is negligible) the P.D. of the cell changes (after a short latent period) from about 10 mv. negative to about 28 mv. positive and then slowly returns approximately to its original value (Fig. 1, p. 14). This appears to depend chiefly on changes in the apparent mobilities of organic ions in the protoplasm.

The protoplasmic surface is capable of so much change that it does not seem probable that it is a monomolecular layer. It does not behave like a collodion nor a protein film since the apparent mobility of Na+ can increase while that of K+ is decreasing under the influence of guaiacol.
THE COLOR VISION OF DICHROMATS
Authors: Hecht Selig , Shlaer Simon
Published: May 2004

1. Protanopes and deuteranopes show one maximum of wavelength discrimination which occurs near their neutral point in the region of 500 mµ (blue-green for color-normal). The value of the just discriminable wavelength interval Δλ is about 1 mµ at this point and is much like the normal. To either side of this, Δλ rises. It increases rapidly on the short-wave side, and slowly on the long-wave side, rising to about 50 mµ at the two ends of the spectrum.

2. The brightness distribution in the spectrum for dichromats falls only partly outside the range established for color-normals. The protanope curve is narrower than normal, and its maximum lies nearly 15 mµ to the left of it. The deuteranope curves are about the same width as the normal, and their maxima lie slightly but definitely to the right of it. The main difference between protanope and deuteranope spectrum sensitivity lies on the red side of brightness curves, where the deuteranope is strikingly higher. This difference furnishes the only reliable diagnostic sign which may be applied to an individual dichromat for separating the two types.

3. The average position for the neutral point of twenty-one protanopes is 496.5 mµ; of twenty-five deuteranopes 504.3 mµ. The range of variation in the position of neutral point is twice as great for the deuteranope as for the protanope.

4. Dichromatic gauging of the spectrum cannot yield unique mixture values for any wavelength because of the large stretches of poor wavelength discrimination. Data have therefore been secured which locate the spectral ranges that can match specific mixtures of two primaries when brightness differences are eliminated. The form of the data is much the same for a protanope and for a deuteranope; the only difference is in the relative brightness of the primaries.

5. Previously accepted anomalies in the spectral matching of dichromats which have led to the rejection of the third law of color mixture for them, have been eliminated. They are shown to have been due to the non-uniqueness of color matches and the usually disparate brightnesses of the primaries. Color mixture matches for dichromats are valid at all brightnesses.
THE COLOR VISION OF DICHROMATS
Authors: Hecht Selig , Shlaer Simon
Published: May 2004

1. Wavelength discrimination for the colorblind is entirely determined by saturation differences in the spectrum. From the neutral point to the short-wave end, his spectrum may be completely matched by 440 mµ plus white; to the long-wave end by 650 plus white. The proportion of color to white, hence the relative saturation, changes rapidly in the region of small Δλ at the center, and slowly in regions of large Δλ at the ends.

2. The data of spectrum gauging with two primaries (color mixture) by the dichromat are shown to contain the saturation distribution in the spectrum for the dichromat. This is because each mixture of primaries may be considered as composed of a mixture which matches white and of an excess of one primary. The data when so computed yield saturation distributions almost identical with those found by direct measurement, and show that on each side of the neutral point the basis of color mixture for the colorblind lies in saturation and not in hue differences.

3. To judge by these measurements, the spectrum for the protanope and deuteranope is composed of only two hues, themselves probably of low saturation, situated one at each end. Toward the center these hues decrease still more in saturation until they completely disappear in the white of the neutral point.
TEMPERATURE AND CRITICAL ILLUMINATION FOR REACTION TO FLICKERING LIGHT
Authors: Crozier W. J. , Wolf Ernst , Zerrahn-Wolf Gertrud
Published: May 2004

The curve connecting mean critical illumination (Im) and flicker frequency (F) for response of the sunfish Lepomis (Enneacanthus gloriosus) to flicker is systematically displaced toward lower intensities by raising the temperature. The rod and cone portions of the curve are affected in a similar way, so that (until maximum F is approached) the shift is a nearly constant fraction of Im for a given change of temperature. These relationships are precisely similar to those found in the larvae of the dragonfly Anax. The modifications of the variability functions are also completely analogous. The effects found are consistent with the view that response to flicker is basically a matter of discrimination between effect of flashes of light and their after effects,—a form of intensity discrimination. They are not consistent with the stationary state formulation of the shape of the flicker curve.

An examination of the relationships between the cone portion and the rod portion of the curves for the sunfish suggests a basis for their separation, and provides an explanation for certain "anomalous" features of human flicker curves. It is pointed out how tests of this matter will be made.
THE POTENTIAL AND RESPIRATION OF FROG SKIN
Authors: Ponder Eric , Macleod John
Published: May 2004

Measurements of the O2 consumption and of the potential of frog skin, made under comparable conditions, show that the homologous carbamates (ethyl, propyl, butyl, and amyl) reduce both the O2 consumption and the potential, but not in a similar manner. In this respect, the effect of the carbamates is like the effect of reduction in O2 tension. The simple lysins (saponin and the bile salts), on the other hand, abolish the potential without reducing the O2 consumption at all.

Irrespective of whether one considers the concentration of carbamate in the entire system or the amount of carbamate adsorbed by the frog skin, Traube's rule relating the effect of a carbamate to its position in the homologous series does not seem to apply.
THE COAGULATION OF MYOSIN IN MUSCLE
Authors: Mirsky A. E.
Published: May 2004

1. Muscle can be prepared in the form of a dry powder in which myosin exists in a state similar to that in intact muscle. As in intact muscle, myosin in powdered muscle is soluble and can be caused to rapidly coagulate.

2. Restoring to powdered muscle the quantity of water previously removed causes coagulation of myosin. The rate of coagulation is considerably slower at 0° than at 20°.

3. Adding the powder to a large volume of dilute salt solution also results in coagulation.

4. The water soluble constituents of muscle can be removed from the powder without thereby causing coagulation. Coagulation occurs in water extracted muscle when it is suspended in a dilute salt solution.

5. Coagulation of myosin in muscle resembles the coagulation of myosin caused by dehydration.

6. Myosin coagulates readily only when it is imbedded in the structure of muscle. The significance for coagulation of the arrangement of myosin particles in muscle has been indicated.
A PHASE RULE STUDY OF THE PROTEINS OF THE BLOOD SERUM: A COMPARISON OF THE PROTEINS OF HUMAN, RAT, AND HORSE SERUM
Authors: Jameson Eloise , Roberts Dorothy Brown
Published: May 2004

There are four different kinds of protein in blood serum as shown by the solubility curves.

They must be either single proteins, several continuous series of compounds, or solid solutions.

The solid protein phases are hydrated.

There are definite sex and species differences.
THE EFFECT OF HYDROGEN ION CONCENTRATION UPON THE INDUCTION OF POLARITY IN FUCUS EGGS
Authors: Whitaker D. M.
Published: May 2004

1. The eggs of Fucus furcatus develop perfectly in sea water acidified to pH 6.0. They are retarded at pH 5.5. At pH 5.0 they do not develop, nor do they cytolize.

2. In normal sea water in the dark at 15°C., eggs develop rhizoids on the sides in the resultant direction of a mass of neighboring eggs. The polarity and the whole developmental pattern of the embryo is thereby induced. This inductive effect does not operate, however, unless the directing mass is an appreciable aggregation of cells (10 or more), or unless there are numerous other eggs in the dish. A group of five eggs alone in a dish do not carry out mutual inductions. Two eggs alone in a dish do not develop rhizoids toward each other.

3. When the sea water is acidified to pH 6.0 all sizes of aggregations carry out mutual inductions. Two eggs alone in a dish now develop rhizoids on the sides toward each other, provided they are not more than about 4 egg diameters apart.

4. Increased hydrogen ion concentration thus augments or intensifies the mutual inductive effect.

5. This may explain why only larger masses of eggs show inductions in normal sea water, since presumably the larger masses considerably increase the hydrogen ion concentration locally.

6. The nature of the inductive action is discussed.

7. In acidified sea water at pH 6.0, compared with normal sea water at pH 7.8–8.0, the rhizoids originate and extend with a strongly increased downward component. The substrate then forces further extension or growth of the rhizoid to be in the plane of the substrate.
FLICKER AND THE REACTIONS OF BEES TO FLOWERS
Authors: Wolf Ernst , Zerrahn-Wolf Gertrud
Published: May 2004

Bees were conditioned to collect food on natural and artificial flower beds, parts of which could be set into rotation or side to side movement. Through the relative motion of the flowers the number of alternating stimuli upon the bee's eye is increased. Due to the fact that bees show a strong reaction to intermittent optical stimulation, the proportion of bees settling on the moving section of the flower bed is increased. It seems probable therefore that the visual reaction of bees to flowers in nature is largely due to the flicker effect produced through the motion of the bees relative to the flowers.
THE EFFECT OF ORGANIC IONS ON THE MEMBRANE POTENTIAL OF NERVES
Authors: Wilbrandt W.
Published: May 2004

1. The effect of osmotic pressure on the nerve resting potential of frog sciatic nerve is in accordance with the assumption of a membrane potential; increased osmotic pressure raises, decreased osmotic pressure lowers the potential.

2. The potential of crab nerves is affected by organic and inorganic cations in the approximate series:

Rb > K = diamylamine > dibutylamine > guanidine > tetraethylamine > diethylamine = dimethylamine > dipropylamine > tetramethylamine = choline = Na = Li.

3. The response of the potential to the series of dialkylamines (first decrease, then increase of response ascending in the series) is best understood by the assumption that the nerve membrane is a porous structure.

4. With respect to these salts as well as to other organic cations the dried collodion membrane as a model of a porous membrane shows a striking parallelism to the nerve membrane.

5. Both inorganic and organic anions (NO3, SCN, acetate, propionate, butyrate, lactate, pyruvate) have a definite, if slight, effect in raising the potential of crab nerves. This effect of anions indicates that the nerve membrane is not completely anion impermeable.

6. The effect of organic ions is, with certain restrictions, reversible. Its possible relation to the resting potential and to the after potentials of the electrical disturbance is discussed.

7. The response of the myelinated sciatic nerve of the frog and of the non-myelinated nerve of the spider crab show considerable agreement. There are some definite differences which are, however, not necessarily due to differences of the cell membranes involved, but may be ascribed to the difference of ionic conditions in Ringer and sea water.
REACTIONS OF LIMULUS TO ILLUMINATED FIELDS OF DIFFERENT AREA AND FLICKER FREQUENCY
Authors: Wolf Ernst , Zerrahn-Wolf Gertrud
Published: May 2004

In phototropic tests with young Limulus, the phototropic reactions to flickering fields were studied. If the two fields are equal in area and brightness but different in flicker frequency, the number of animals going to the two fields is proportional to their flicker frequencies. Equal stimulating effects of two fields differing in flicker frequency are obtained by reduction of the area of the faster flickering field. The areas for equal effect must be inversely proportional to their flicker frequencies. It seems that equal effects are dependent upon equality of the number of active excitation elements per unit of time.
IMMUNOLOGICAL STUDIES ON PEPSIN AND PEPSINOGEN
Authors: Seastone C. V. , Herriott R. M.
Published: May 2004

1. Alkali (pH 7.6)-denatured pepsins from swine, cattle, and guinea pigs precipitate in swine pepsin antiserum. Similarly treated pepsins from the rabbit, chicken, and shark do not.

2. Pepsin antisera react with both pepsin and pepsinogen, but do not react with the serum proteins from the homologous species.

3. Pepsinogen antisera react with pepsinogen, but not with twice crystallized pepsin, nor with the serum proteins from the homologous species. Positive reactions between activated pepsinogen and pepsinogen antiserum have been observed. It was possible to remove the reacting material from either the pepsinogen or the activated pepsinogen mixture.

4. Antisera made with serum proteins do not react with the homologous pepsin or pepsinogen.
THE INFLUENCE OF LIGHT ADAPTATION ON SUBSEQUENT DARK ADAPTATION OF THE EYE
Authors: Hecht Selig , Haig Charles , Chase Aurin M.
Published: May 2004

The course of dark adaptation of the human eye varies with the intensity used for the light adaptation which precedes it. Preadaptation to intensities below 200 photons is followed only by rod adaptation, while preadaptation to intensities above 4000 photons is followed first by cone adaptation and then by rod adaptation.

With increasing intensities of preadaptation, cone dark adaptation remains essentially the same in form, but covers an increasing range of threshold intensities. At the highest preadaptation the range of the subsequent cone dark adaptation covers more than 3 log units.

Rod dark adaptation appears in two types—a rapid and a delayed. The rapid rod dark adaptation is evident after preadaptations to low intensities corresponding to those usually associated with rod function. The delayed rod dark adaptation shows up only after preadaptation to intensities which are hundreds of times higher than those which produce the maximal function of the rods in flicker, intensity discrimination, and visual acuity. The delayed form remains essentially constant in shape following different intensities of preadaptation. However, its time of appearance increases with the preadaptation intensity; after the highest preadaptation, it appears only after 12 or 13 minutes in the dark.

These two modes of rod dark adaptation are probably the expression of two methods of formation of visual purple in the rods after its bleaching by the preadaptation lights.
DO MELANOPHORE NERVES SHOW ANTIDROMIC RESPONSES?
Authors: Parker G. H.
Published: May 2004

1. In Fundulus heteroclitus the dispersing melanophore nerve fibers have a relatively high threshold for faradic stimulation and a low one for stimulation by cutting. When they are protected from the competing action of the concentrating fibers, they show through the responses of their melanophores well marked antidromic activities which can also be seen to a slight degree even where the concentrating fibers are active.

2. The concentrating melanophore nerve fibers in this fish have a relatively low threshold for faradic stimulation and a high one for stimulation by cutting. They also exhibit clear antidromic responses as shown by their associated melanophores.
STUDIES ON THE DIFFUSION EFFECT UPON IONIC DISTRIBUTION
Authors: Teorell Torsten
Published: May 2004

The aim of this paper is to present confirmation of the theory of the diffusion effect. By diffusion effect is understood a redistribution of the ions in a system where a continuous diffusion of one electrolyte is going on, which results in a steady state showing accumulation and impoverishment of certain ions.

Some typical experiments are recorded and discussed. The results are found in satisfactory agreement with the theory: this can be demonstrated in several ways.

The importance of considering activity changes is pointed out. Water migration and the diffusion membrane probably have no appreciable influence upon the diffusion effect under the conditions of these experiments.

The diffusion effect may have biological analogies.
THE EFFECT OF HYDROGEN ION CONCENTRATION UPON THE INDUCTION OF POLARITY IN FUCUS EGGS
Authors: Whitaker D. M. , Lowrance E. W.
Published: May 2004

1. When a Fucus egg develops near one end in a close fitting capillary tube of pyrex glass or silica (quartz), diffusion of substances passing to and from the egg is more impeded on the side of the egg toward the far end of the tube.

2. The egg therefore develops in a gradient of its own diffusion products, and of oxygen tension.

3. More than 600 eggs have been reared, each near one end in a capillary, in sea water at various regulated and measured pH values.

4. When the medium, which is initially homogeneous inside and outside the capillary, is initially at pH 6.5 to 7.6, nearly all of the eggs develop rhizoid protuberances on the sides of the eggs toward the far ends of the capillaries. This is on the sides of the eggs where the concentration of substances diffusing from the eggs is greatest.

5. The polarity and developmental pattern of the egg is thus determined either by a concentration gradient of products diffusing from it, or by a gradient of oxygen tension. The former interpretation is favored.

6. This is regarded as an extension of earlier observations that rhizoid protuberances form on the sides of two neighboring eggs in the direction of the neighbor if the sea water is acidified.

7. It appears hardly possible that a mitogenetic effect could be responsible for the response of an egg to its own diffusion gradients.

8. When the medium is made more basic, the percentage of the eggs which form rhizoid protuberances toward the far end of the tube decreases to about 20 or 25 per cent between pH 8.1 and 8.6. The response of the egg to the gradients which it produces is thus statistically reversed. The determination of the polarity of the eggs by the diffusion gradients does not become as complete in alkalinized as in acidified sea water.

9. When the pH of the sea water is elevated to 9.1 or 9.2, salts precipitate out. The type of development is altered and the control of the diffusion gradients over the polarity of the eggs decreases.
THE RELATION BETWEEN VISUAL ACUITY AND ILLUMINATION
Authors: Shlaer Simon
Published: May 2004

1. An apparatus for measuring the visual acuity of the eye at different illuminations is described. The test object is continuously variable in size and is presented at a fixed distance from the eye in the center of a 30° field. Observation of the field is through an artificial pupil. The maximum intensity obtainable is more than enough to cover the complete physiological range for the eye with white light though only 110 watts are consumed by the source. Means for varying the intensity over a range of 1:1010 in small steps are provided.

2. The relation of visual acuity and illumination for two trained observers was measured, using two different types of test object, a broken circle and a grating. The measurements with both test objects show a break at a visual acuity of 0.16, all values below that being mediated by the rods and those above by the cones. The grating gives higher visual acuities at intensities less than about 30 photons and lower visual acuities above that. The maximum visual acuity attainable with the grating under the same conditions is about 30 per cent lower than that with the C. It is shown that the limiting factor in the resolution of the eye for the grating is the diameter of the pupil when it is less than 2.3 mm. and the size of the central cones when the pupil is larger than that. The value of the diameter of the cone derived on that basis from the visual acuity data agrees with that derived from direct cone count in a unit of area.

3. The data for the cones made with both test objects are adequately described by one and the same form of the stationary state equation derived by Hecht for the photoreceptor system. This fact, together with certain considerations about the difference in the nature of the two test objects with regard to the resolvable area, leads to the conclusion that detail perception is a function of a distance rather than an area. All the data for the rods can likewise be described by another variety of the same equation, although the data are too fragmentary to make the choice of the form as certain as might be desired.
TRANSVERSE ELECTRIC IMPEDANCE OF NITELLA
Authors: Curtis Howard J. , Cole Kenneth S.
Published: May 2004

Alternating current measurements have been taken on single Nitella cells over a frequency range from 30 to 2,500,000 cycles per second with the current flow perpendicular to the axis of the cell. The measuring cells were so constructed that electrolytes of any desired concentration could be circulated during the course of the measurements. The cellulose wall which surrounds the cell is found to play an important part in the interpretation of the results obtained. In a mature cell, this cellulose has a specific resistance of about 1000 ohm cm. which is independent of the medium in which the cell is suspended. The thickness of the wall is computed to be about 10 µ. The cell membrane is found to be virtually non-conducting, and to have a capacity of 0.94 µf./cm.2 ± 10 per cent and a phase angle of 80° ± 4°.

The specific resistances of the sap were difficult to compute from data on living cells and were unsatisfactory because they were very much dependent upon the medium, while measurements on extracted sap gave 58 ohm cm. ± 8 per cent which was independent of the medium. There are indications that the chloroplasts have impedance properties similar to those of living cells.
A PHASE RULE STUDY OF THE PROTEINS OF BLOOD SERUM
Authors: Jameson Eloise , Roberts Dorothy Brown
Published: May 2004

A method has been developed for applying the phase rule to systems of several protein components in serum.

The globulin fractions which have been investigated appear to be homogeneous substances.
STUDIES ON ENZYMATIC HISTOCHEMISTRY
Authors: Glick David
Published: May 2004

The activity-pH relationship for choline esterase from horse serum, gastric mucosa of the pig, and cat brain was investigated, and an optimum was observed at pH 8.5 in each case.

A micro method for the determination of choline esterase was developed capable of measuring the hydrolysis down to the order of that given by 1 x 10–8 mol of ester.
CRITICAL ILLUMINATION AND FLICKER FREQUENCY, AS A FUNCTION OF FLASH DURATION: FOR THE SUNFISH
Authors: Crozier W. J. , Wolf E. , Zerrahn-Wolf G.
Published: May 2004

From the relations between critical illumination in a flash (Im) and the flash frequency (F) for response of the sunfish to visual flicker when the proportion of light time to dark time (tL/tD) in a flicker cycle is varied at one temperature (21.5°) the following results are obtained:

At values of tL/tD between 1/9 and 9/1 the F - log Im curves are progressively shifted toward higher intensities and lower Fmax.. Fmax. is a declining rectilinear function of the percentage of the flash cycle time occupied by light.

The rod and the cone portions of the flicker curve are not shifted to the same extent.

The cone portion and the rod region of the curve are each well described by a probability integral. In terms of F as 100 F/Fmax. the standard deviation of the underlying frequency distribution of elemental contributions, summed to produce the effect proportional to F, is independent of tL/tD.

The magnitude of log Im at the inflection point (r'), however, increases rectilinearly with the percentage light time in the cycle.

The proportionality between Im and σII1 is independent of tL/tD.

These effects are interpreted as consequences of the fact that the number of elements of excitation available for discrimination of flicker is increased by increasing the dark interval in a flash cycle. Decreasing the dark interval has therefore the same kind of effect as reducing the visual area, and not that produced by decreasing the temperature.
THE CONCENTRATION EFFECT WITH VALONIA: POTENTIAL DIFFERENCES WITH DILUTED POTASSIUM-RICH SEA WATERS
Authors: Damon E. B.
Published: May 2004

The concentration effect with sea waters containing more than the normal amount of potassium has been studied in Valonia macrophysa. This was done by comparing the initial changes in P.D. across the protoplasm when natural sea water bathing the cell was replaced by various isotonic dilutions of KCl-rich sea waters.

With small dilutions of KCl-rich sea waters, the P.D.-time curves are of the same form as with the undiluted solution, exhibiting the fluctuations characteristic of KCl-rich solutions. This indicates that with these solutions K+ enters Valonia protoplasm and plays an important part in the P.D. The value of the initial rise in P.D. decreases with increasing dilution.

With high dilutions of KCl-rich sea waters, the P.D.-time curves are of quite different shape, resembling the curves with diluted natural sea water; the P.D. is practically independent of small changes in the concentration of potassium, and increases with increasing dilution. That is, with these higher dilutions, the sign of the concentration effect is reversed, becoming the same as with diluted natural sea water.

The greater the concentration of KCl in the undiluted sea water, the higher is the critical dilution at which K+ ceases to influence the P.D.

For a wide range of sea waters containing both KCl and NaCl, it is shown that the concentration effect above the critical dilution is determined solely by the activity of NaCl in the external solution. It is concluded that with dilute natural sea water and with high dilutions of KCl-rich sea waters we have to do with a diffusion potential, involving only the Na+ and Cl- ions, which are diffusing out from the vacuole.

A quantitative relation between the composition of the sea water and the critical dilution has been deduced from the classical theory of the diffusion of electrolytes. It is shown that with dilutions less than this critical value the diffusion of K+ in the outer non-aqueous layer of the protoplasm is directed inward; hence K+ enters the protoplasm from these solutions. With dilutions greater than the critical value, the diffusion of K+ in this layer is directed outward; hence K+ does not enter the protoplasm.

Since the P.D. shows no evidence of this outward diffusion of K+, it is concluded that the amount of K+ ordinarily present in the protoplasm is too small to produce any lasting electrical effect, and that the outward diffusion of K+ from the vacuole is prevented by the mechanism responsible for the accumulation of KCl in the cell sap.
ISOLATION, CRYSTALLIZATION, AND PROPERTIES OF SWINE PEPSINOGEN
Authors: Herriott Roger M.
Published: May 2004

1. A method is described for the preparation of pepsinogen from swine gastric mucosae which consists of extraction and fractional precipitation with ammonium sulfate solutions followed by two precipitations with a copper hydroxide reagent under particular conditions. Crystallization as very thin needles takes place at 10°C., pH 5.0 and from 0.4 saturated ammonium sulfate solution containing 3–5 mg. protein nitrogen per milliliter.

2. Solubility measurements, fractional recrystallization, and fractionation experiments based on separation after partial heat or alkali denaturation and after partial reversal of heat or alkali denaturation failed to reveal the presence of any protein impurity.

3. The properties of the enzymatically inactive pepsinogen were studied and compared with the properties of crystalline pepsin. The properties of pepsinogen which are similar to those of pepsin are: molecular weight, absorption spectrum, tyrosine-tryptophane content, and elementary analysis. The properties in which they differ are: enzymatic activity, crystalline form, amino nitrogen, titration curve, pH stability range, specific optical rotation, isoelectric point, and the reversibility of heat or alkali denaturation.

4. Conversion of pepsinogen into pepsin at pH 4.6 was found to be autocatalytic; i.e., the pepsin formed catalyzes the reaction. Conversion of pepsinogen into pepsin is accompanied by the splitting off of a portion of the molecule containing 15–20 per cent of the pepsinogen nitrogen.
CALCULATIONS OF BIOELECTRIC POTENTIALS
Authors: Hill S. E. , Osterhout W. J. V.
Published: May 2004

Cells of Nitella have been studied which behave differently from those described in earlier papers. They show unexpectedly large changes in P.D. with certain concentrations of KCl. This is due to the production of action currents (these are recorded at the spot where KCl is applied).

A method is given for the separate evaluation of changes of P.D. due to partition coefficients and those due to mobilities.

A new amplifier and an improved flowing contact are described.