bluuebunny/crossref_metadata_2025 huggingface dataset:
THE SENSIBILITY OF THE SUN-FISH, LEPOMIS, TO MONOCHROMATIC RADIATION OF LOW INTENSITIES
Authors: Grundfest Harry
Published: May 2004

1. A test is proposed of the hypothesis that visual purple is the photosensitive substance concerned in dim vision. It is based on the fact that fish visual purple is different from that of other vertebrates. If the hypothesis is correct, the fish dim-visibility function should be different from that of other vertebrates and should be determined by the absorption spectrum of its visual purple.

2. A new method is described for obtaining the visibility function of fish, in quantitative terms. It depends on the measurement of the least amounts of various spectral energies which will produce a visual orienting response to the displacement of a constant background.

3. Data are presented on thirteen animals. It is shown that the maximum of the visibility function is identical with the maximum of the absorption spectrum of fish visual purple. The shapes of the visibility curves obtained are, however, variable and different from that of the absorption spectrum.

4. The possibility that Lepomis visual purple is different from that of other fish is ruled out by a series of measurements which confirm the results of Koettgen and Abelsdorff on other fish.

5. Reasons are given for the conclusion that there are present in Lepomis special conditions which distort the visibility curve out of true agreement with that predictable from the absorption spectrum of its visual purple. The suggestion is made that the presence of light absorbing, but not light sensitive, pigments is responsible for this distortion. One of these pigments may perhaps be carotin while the second is unspecified.
THE TEMPERATURE CHARACTERISTIC OF RESPIRATION OF AZOTOBACTER
Authors: Lineweaver Hans , Burk Dean , Horner C. Kenneth
Published: May 2004

The temperature characteristic of respiration of Azotobacter vinelandii possesses a constant value of 19,330 ± 165 over the temperature range 20–30°C. This value is independent of pH, oxygen tension, age of culture, and other factors within the limits studied.

The optimum temperature of respiration is 34–35°C., with limits at about 10° and 50°C.
ELECTROKINETIC PHENOMENA
Authors: Abramson Harold A.
Published: May 2004

1. By combining the theories of Smoluchowski, Debye and Hückel, and Henry it is possible to state explicitly (making necessary assumptions) under what conditions the following simple rule should be valid for proteins:

In solutions of the same ionic strength, the electric mobilities of the same protein at different hydrogen ion activities should be proportional to the number of hydrogen (hydroxyl) ions bound.

2. Data of Tiselius and of the writer confirm this rule for (a) egg albumin, (b) serum albumin, (c) deaminized gelatin and gelatin, and (d) casein.

3. On the basis of the confirmed theory the titration curves of certain proteins are predicted from their mobilities.

4. It is shown that when certain proteins are adsorbed by quartz the apparent dissociation constant of the adsorbed protein is practically unchanged. The mass law must also be valid at the phase boundary.

5. The facts of paragraphs (1) to (4) are discussed in connection with the mechanism of (a) protein adsorption, (b) enzyme activity, (c) immune reactions, (d) the calculation of the electric charge of cells, and (e) criteria of surface similarity.
ELECTROKINETIC PHENOMENA
Authors: Abramson Harold A. , Grossman E. B.
Published: May 2004

The specific rotation of egg albumin, gliadin, and gelatin (40°C.) is discussed in connection with available data on (a) mobility, (b) titration curve, and (c) osmotic pressure. It seems likely that the change in specific rotation with pH of protein solutions is proportional to the change in net charge.
PROTOPLASMIC POTENTIALS IN HALICYSTIS
Authors: Blinks L. R.
Published: May 2004

The potential difference across the protoplasm of impaled cells of two American species of Halicystis is compared. The mean value for H. Osterhoutii is 68.4 mv.; that for H. ovalis is 79.7 mv., the sea water being positive to the sap in both.

The higher potential of H. ovalis is apparently due to the higher concentration of KCl (0.3 M) in its vacuolar sap. When the KCl content of H. Osterhoutii sap (normally 0.01 M or less) is experimentally raised to 0.3 M, the potential rises to values about equal to those in H. ovalis.

The external application of solutions high in potassium temporarily lowers the potential of both, probably by the high mobility of K+ ions. But a large potential is soon regained, representing the characteristic potential of the protoplasm. This is about 20 mv. lower than in sea water.

The accumulation of KCl in the sap of H. ovalis is apparently not due to the higher mobility of K+ ion in its protoplasm, since the electrical effects of potassium are practically identical in H. Osterhoutii, where KCl is not accumulated.
ON THE MEASURE OF EXCITABILITY
Authors: Blair H. A.
Published: May 2004

Recent time-intensity data by Rushton (1932) on the sciatic nerve of the frog are shown to provide additional support to the writer's suggestion (1932, a) that integrals of the equation

See PDF for Equation

where V is the applied voltage, p is the local excitatory process and K and k are constants adequately represent the just effective direct current stimuli when the threshold value of p is made a linear function of the voltage of the form h ± α V where h and α are constants.

The measurement of excitability is discussed and it is shown that the criteria for "true" measurements are not likely to be found by the agreement of the data with canonical time-intensity functions as suggested by Lapicque (1931) but rather in the establishing of standard experimental conditions. These conditions may permit the use of chronaxie as a measure of excitability, but it seems more likely that the constant k of the above equation will have to be adopted. There is sufficient evidence to cast considerable doubt on the validity of any conclusions drawn from the existing measurements of chronaxie although those derived through a particular technique may be valid. The problem requires a thorough experimental investigation in terms of integrals of the above equation.
ON TEMPERATURE CHARACTERISTICS FOR DIFFERENT PROCESSES IN THE SAME ORGANISM
Authors: Stier T. J. B. , Wolf Ernst
Published: May 2004

The temperature characteristics (µ) for two activities (heart beat and respiratory movements) studied simultaneously in the same individual organism (Daphnia magna) were always found to differ in magnitude. The type of graph obtained when the frequency of these movements was plotted according to the Arrhenius equation was also distinctly different for each activity. The organism therefore does not determine a uniform magnitude of the temperature characteristic for each of its activities; the values of µ must therefore have, to this extent, a local, specific meaning.
BIOELECTRIC POTENTIALS IN VALONIA
Authors: Damon E. B.
Published: May 2004

The P.D. across the protoplasm of Valonia macrophysa has been studied while the cells were exposed to artificial solutions resembling sea water in which the concentration of KCl was varied from 0 to 0.500 mol per liter. The P.D. across the protoplasm is decreased by lowering and increased by raising the concentration of KCl in the external solution. Changes in P.D. with time when the cell is treated with KCl-rich sea water resemble those observed with cells exposed to Valonia sap.

Varying the reaction of natural sea water from pH 5 to pH 10 has no appreciable effect on the P.D. across Valonia protoplasm. Similarly, varying the pH of KCl-rich sea water within these limits does not alter the height of the first maximum in the P.D.-time curve. The subsequent behavior of the P.D., however, is considerably affected by the pH of the KCl-rich sea water. These changes in the shape of the P.D.-time curve have been interpreted as indicating that potassium enters Valonia protoplasm more rapidly from alkaline than from acidified KCl-rich sea water. This conclusion is discussed in relation to certain theories which have been proposed to explain the accumulation of KCl in Valonia sap.

The initial rise in P.D. when a Valonia cell is transferred from natural sea water to KCl-rich sea water has been correlated with the concentrations of KCl in the sea waters. It is assumed that the observed P.D. change represents a diffusion potential in the external surface layer of the protoplasm, where the relative mobilities of ions may be supposed to differ greatly from their values in water. Starting with either Planck's or Henderson's formula, an equation has been derived which expresses satisfactorily the observed relationship between P.D. change and concentration of KCl. The constants of this equation are interpreted as the relative mobilities of K+, Na+, and Cl- in the outer surface layer of the protoplasm. The apparent relative mobility of K+ has been calculated by inserting in this equation the values for the relative mobilities of Na+ (0.20) and Cl- (1.00) determined from earlier measurements of concentration effect with natural sea water. The average value for the relative mobility of K+ is found to be about 20. The relative mobility may vary considerably among different individual cells, and sometimes also in the same individual under different conditions.

Calculation of the observed P.D. changes as phase-boundary potentials proved unsatisfactory.
ULTRAFILTRATION
Authors: Greenberg David M. , Greenberg Max M.
Published: May 2004

Assuming that "bound" water loses its solvent properties, it is shown by an ultrafiltration method that in solutions of gelatin, casein, starch, and glycogen, and in blood serum, only a very small fraction of the water can be associated with the colloids in this form.
ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. VIII
Authors: Crozier W. J. , Pincus G.
Published: May 2004

The upward geotropic orientation (angle θ) of adult rats (race A) has been measured as a function of slope of substratum. The relative variation of orientation angle is a declining rectilinear function of θ. The fraction of the total observable variation of performance (θ) which is controlled by the intensity of excitation (56 per cent) is identical with that found for young rats of the same strain, although the total variation is a little greater.

Injection of adrenin distorts the θ vs. α graph in a manner quite concordant with the effect obtained in young rats. With the adults the absolute magnitudes of the variations of θ, at corresponding intensities of excitation, are not affected by the action of adrenin, and, as with the young, the proportion of modifiable variation of θ is not altered. The variability of performance, considered as a function of the performance, must therefore be regarded as an organic invariant. Certain consequences of this finding are referred to.
QUANTITATIVE ASPECTS OF CUTANEOUS SENSORY ADAPTATION. I
Authors: Hoagland Hudson
Published: May 2004

1. Adaptation of tactile receptors in the skin of the frog to excitation by an intermittent jet of air is measured and correlated with certain properties of a series of notched discs used to interrupt the air stream.

2. Adaptation in fifteen cases is found to be described by either one of two empirical formulas,

or

t = -k log f + C, for nine preparations

t = a f-b, for six preparations

where f is the per cent frequency at time t and -k and -b are constants defining the rate of adaptation.
THE THEORY OF DIFFUSION IN CELL MODELS
Authors: Longsworth Lewis G.
Published: May 2004

The differential equations which describe the simultaneous diffusion of water and a salt in a cell model have been formulated and solved. The equations have been derived from the general laws which describe diffusion processes, thereby furnishing a physical interpretation for the constants which enter into the theory. The theoretical time curves for the two diffusing substances are in good agreement with the experimentally determined curves and accurately reproduce all of the essential characteristics of the experiment.
INTERMITTENT STIMULATION BY LIGHT
Authors: Hecht Selig , Verrijp Cornelis D.
Published: May 2004

When measurements of the critical fusion frequency for white light over a large range of intensities are made with the rod-free area of the fovea, the relation between critical frequency and log I is given by a single sigmoid curve, the middle portion of which approximates a straight line whose slope is 11.0. This single relation must be a function of the foveal cones.

When the measurements are made with a retinal area placed 5° from the fovea, and therefore containing both rods and cones, the relation between critical frequency and log I shows two clearly separated sections. At the lower intensities the relation is sigmoid and reaches an upper level at about 10 cycles per second, which is maintained for 1.25 log units, and is followed by another sigmoid relationship at the higher intensities similar to the one given by the rod-free area alone.

These two parts of the data are obviously separate functions of the rods at low intensities and of the cones at high intensities. This is further borne out by similar measurements made with retinal areas 15° and 20° from the fovea where the ratio of rods to cones is anatomically greater than at 5°. The two sections of the data come out farther apart on the intensity scale, the rod portion being at lower intensities and the cone portion at higher intensities than at 5°.

The general form of the relation between critical frequency and intensity is therefore determined by the relative predominance of the cones and the rods in the retinal area used for the measurements.
THE "BOUND" WATER OF BIOLOGICAL COLLOIDS: A REPLY
Authors: Greenberg David M. , Cohn Waldo E.
Published: May 2004

The objection by Bull to the estimation of bound water by ultrafiltration, because of an assumed adsorption of the reference substance, has been found invalid for glucose. No adsorption of glucose by the proteins, casein and gelatin, could be detected.

The estimation of the bound water of proteins from the probable surface adsorption of water by proteins leads to only a small value.
THE APPLICATION OF QUANTUM MECHANICS TO CERTAIN CASES OF HOMOGENEOUS CATALYSIS. I
Authors: Stearn Allen E.
Published: May 2004

1. The activation energy for the hydrolytic breaking of a peptid linkage has been calculated from quantum mechanical considerations.

2. The relative catalytic effects of H+ and OH- and the mechanism of these effects have been calculated and discussed.

3. These effects are both qualitatively and semiquantitatively in agreement with experiment.
STIMULATION BY COLD IN NITELLA
Authors: Hill Samuel E.
Published: May 2004

Sudden local chilling causes action currents to be set up in Nitella and in Chara, an effect which does not follow gradual local chilling. This may be due to a partial solidification of the non-aqueous protoplasmic surfaces which makes them susceptible to rupture by the protoplasmic streaming. This movement continues usually for several minutes after the chilling, whereas if stimulation occurs at all it occurs immediately on chilling. It is found that a chilled spot is much more sensitive to mechanical stimulation than is a spot at room temperature.

Chilling is accompanied by a rise of resistance, a lowered rate of recovery following stimulation, and usually by a falling off in the magnitude of the action curve.
CRYSTALLINE CHYMO-TRYPSIN AND CHYMO-TRYPSINOGEN
Authors: Kunitz M. , Northrop John H.
Published: May 2004

A new crystalline protein, chymo-trypsinogen, has been isolated from acid extracts of fresh cattle pancreas. This protein is not an enzyme but is transformed by minute amounts of trypsin into an active proteolytic enzyme called chymo-trypsin. The chymo-trypsin has also been obtained in crystalline form.

The chymo-trypsinogen cannot be activated by enterokinase, pepsin, inactive trypsin, or calcium chloride. There is an extremely slow spontaneous activation upon standing in solution.

The activation of chymo-trypsinogen by trypsin follows the course of a monomolecular reaction the velocity constant of which is proportional to the trypsin concentration and independent of the chymotrypsinogen concentration. The rate of activation is a maximum at pH 7.0–8.0. Activation is accompanied by an increase of six primary amino groups per mole but no split products could be found, indicating that the activation consists in an intramolecular rearrangement. There is a slight change in optical activity but no change in molecular weight.

The physical and chemical properties of both proteins are constant through a series of fractional crystallizations.

The activity of chymo-trypsin decreases in proportion to the destruction of the native protein by pepsin digestion or denaturation by heat or acid.

Chymo-trypsin has powerful milk-clotting power but does not clot blood plasma and differs qualitatively in this respect from the crystalline trypsin previously reported. It hydrolyzes sturin, casein, gelatin, and hemoglobin more slowly than does crystalline trypsin but the hydrolysis of casein is carried much further. The hydrolysis takes place at different linkages from those attacked by trypsin. The optimum pH for the digestion of casein is about 8.0–9.0. It does not hydrolyze any of a series of dipeptides or polypeptides tested.

Several chemical and physical properties of both proteins have been determined.
TEMPERATURE CHARACTERISTICS FOR HEART BEAT FREQUENCY IN MICE
Authors: Crozier W. J. , Pincus G. , Renshaw B.
Published: May 2004

An apparatus is described which permits the simultaneous recording of body temperature and heart beat frequency in young mice. When heart beat frequency is related to body temperature the values of the temperature characteristic for the inbred albino strain used are 22,400– calories over the range 15 to 20°+, 16,000± calories from 20+ to 27°, and 11,000± calories from 27 to 35°+.
ELECTRICAL FACTORS INFLUENCING THE RATE OF FILTRATION OF AQUEOUS ELECTROLYTE SOLUTIONS THROUGH CELLOPHANE MEMBRANES
Authors: White H. L. , Monaghan Betty , Urban Frank
Published: May 2004

The mechanisms by which electrokinetic factors might influence the filtration rate of aqueous electrolyte solutions through membranes are discussed. The filtration rate of a thorium chloride solution in which the membrane is isoelectric is compared with those of other solutions. The maximum filtration rate is found at the isoelectric concentration, the rate falling as the electrokinetic potential increases.

The results demonstrate an inverse relation between the electrokinetic potential and the filtration rate but do not permit the evaluation with any great exactitude of the respective rôles played by the two proposed mechanisms, namely, a stream potential-electroosmotic back-transport and a variation in effective pore diameter due to an orientation of water dipoles determined by electrical factors.

Evidence is presented that Lepeschkin's membrane resistance is an artifact.
RESTORATION OF THE POTASSIUM EFFECT BY MEANS OF ACTION CURRENTS
Authors: Osterhout W. J. V. , Hill S. E.
Published: May 2004

Treatment with distilled water removes from Nitella the ability to give the large potential difference between 0.01 M KCl and 0.01 M NaCl which is known as the potassium effect. The potassium effect may be restored by action currents. This might be explained by saying that distilled water removes from the surface a substance, R, which is responsible for the potassium effect and which moves into the surface during the action current and thereby restores the potassium effect.
THE CHROMATOPHORAL NEUROHUMORS OF THE DOGFISH
Authors: Parker G. H.
Published: May 2004

1. The common dogfish, Mustelus canis, as is well known, exhibits two temporary extremes of tint, one dark, the other light. The dark phase is induced by a secretion from the pituitary gland which is carried in the blood, hence a substance soluble in water (a hydroneurohumor). The light phase is under the control of nerves and cannot be excited by blood from a light fish.

2. When an olive oil or ether extract is made from the fins of a light dogfish and this extract is injected into a dark fish, large light spots may appear in from 1 to 2 days and persist for several days. These light spots, which may be called secondary spots, are not to be confused with certain small and very temporary light spots, the primary spots, which occur soon after the injection and which are believed to be purely operative in origin.

3. The secondary light spots are not due to the death of the integumentary tissue, for, after their formation, they can be made to disappear by the action of obstetrical pituitrin and will subsequently reappear.

4. They are produced by some substance extracted from the light fins by ether or by olive oil. They are not produced by sea water, ether, or olive oil alone.

5. The extracted substance, which can resist dry heat up to at least 110°C., owes its limited range of action in the dogfish to its inability to dissolve in water. It is soluble in oil (a liponeurohumor).

6. This liponeurohumor is believed to emanate from the nerve terminals concerned with the concentration of melanophore pigment and to spread through the fatty components of the integumentary cells.
ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. IX
Authors: Crozier W. J. , Pincus G.
Published: May 2004

Adult hybrid rats from the cross of races A x B show a total capacity to vary their geotropic performance which is identical with that of their B parents. The proportionate modifiable variability of geotropic orientation also agrees quantitatively with that for the B parents. These relationships are not disturbed by the action of adrenin, which leads to a distortion of the θ vs. α curve. Young rats of the F1 generation show a greater proportion of unmodifiable variation of geotropic orientation. It is pointed out that the present findings support the conclusion that the capacity of rats to exhibit variation of geotropic orientation is limited by their genetically determined composition and that the special condition in the young hybrids may be understood as due to a kind of temporary disharmony of developmental events.
THE RESISTANCE OF DROSOPHILA TO ALCOHOL
Authors: Crozier W. J. , Pincus G. , Zahl P. A.
Published: May 2004

The mean time-to-death (t) of imaginal Drosophila of an inbred line in alcohol vapor of constant partial pressure (P) is a declining rectilinear function of P for each age. The time-to-death depends upon the diffusion into the fly of an amount of alcohol sufficient to kill. It does not depend upon any measurable property of a reaction between the substance of the fly and the alcohol which produces death. The relation between t and P is independent of temperature, but the invasion coefficient S = Δt/ΔP declines with age and differs for the two sexes. The first derivative of S with respect to age exhibits sharp discontinuities. The internal alcohol required to kill declines with age, varying with S. The relative variation of t, σt/t, is directly proportional to the resistance to diffusive penetration of alcohol R, where R = 1/S.

The vapor pressure of alcohol estimated to kill instantaneously shows periodic fluctuations with age; these are precisely correlated with changes in the slope of S as a function of age.

Periodic fluctuations of invasibility by alcohol, and of the lethal dose, are interpreted as due to the incidence of suppressed moults. It is shown that in the accumulation of deaths as a function of time (age) in a genetically uniform population of Drosophila of one sex, similar fluctuations are apparent in the rate. The statistical smoothing of such data is not legitimate.
ELECTRIC IMPEDANCE OF ASTERIAS EGGS
Authors: Cole Kenneth S. , Cole Robert H.
Published: May 2004

The alternating current resistance and capacity of suspensions of unfertilized eggs of Asterias forbesi have been measured at frequencies from one thousand to sixteen million cycles per second.

The plasma membrane of the egg has a static capacity of 1.10µf/cm.2 which is practically independent of frequency. The suspensions show a capacity dependent on frequency at low frequencies which may be attributable to surface conductance.

The specific resistance of the cytoplasm is between 136 and 225 ohm cm. (4 to 7 times sea water), indicating a relatively high concentration of non-electrolytes.

At frequencies above one million cycles there is definite evidence of another element of which the nucleus is presumably a part.
ADAPTATION OF CUTANEOUS TACTILE RECEPTORS
Authors: Rubin Morton A.
Published: May 2004

The potassium content of the skin of Rana pipiens is found to be 132 m.g. per cent. This is roughly of the order of magnitude of the content of potassium in nerve.

Analyses were also made of the skin for Na, Ca, Mg, Cl, S, and P.
ON THE QUANTITY OF ELECTRICITY AND THE ENERGY IN ELECTRICAL STIMULATION
Authors: Blair H. A.
Published: May 2004

Weiss's and Hoorweg's laws are discussed with respect to the dynamics of the excitatory process. The former is shown to have a simple basis which is inadequate, however, because it implies a constant rate of subsidence of the state of excitation. Hoorweg's law does not follow logically from the same basis so the two laws do not represent the same excitatory mechanism. Experimental data do not give minimal energies at 2 rheobases as predicted by each law. The experimental minima with direct currents are at 1.5 or more rheobases, while with condenser stimuli they are from 2.5 to 3.0 rheobases. These minima conform to the predictions of the writer's equations which give the direct current minima as variable with a lower limit at 1.5 rheobases and the condenser minima as constant at e = 2.718 rheobases. The reasons for these differences are discussed and it is concluded that considerations of the quantity of electricity and the energy, per se, do not lead to any simple concepts with regard to the excitatory mechanism. The existing quantity and energy relations are, however, easily correlated in terms of the dynamics of the excitatory mechanism.
COAGULATION OF MYOSIN BY DEHYDRATION
Authors: Mirsky A. E.
Published: May 2004

When myosin is dehydrated it becomes insoluble. The number of detectable SH groups in myosin coagulated by dehydration is the same as in native soluble myosin. In this respect coagulation by dehydration differs from coagulation brought about in any of the other ways now known, but resembles the coagulation that occurs in muscle during rigor and in the egg after fertilization.
SUBSTANCES AFFECTING ADULT TISSUE IN VITRO
Authors: Simms Henry S. , Stillman Nettie P.
Published: May 2004

Digestion of adult tissue with trypsin has been shown to stimulate its initial growth in vitro. This stimulation appeared to result from the removal of an inhibitory material from the tissue due to the proteolytic action of the trypsin.

This paper shows that the fluid after the digestion contains material which inhibits the initial growth of adult chicken aorta tissue.

This tissue inhibitor has been obtained from chicken, dog, and sheep aortas. It is partly precipitated by an equal volume of alcohol, and is more completely precipitated by the further addition of CaCl2 (plus a little NaOH). The inhibitor is destroyed at 100°C. but usually withstands 58°C. for 20 minutes. Moderate tryptic digestion renders it soluble without destroying it. It sometimes withstands dialysis, but at other times is lost.

Its physical and chemical properties, as far as we know them, coincide with those of lactenin (a bacteriostatic substance in milk). Lactenin was found to inhibit adult tissue growth; but the tissue inhibitor failed to restrain bacterial growth.

This tissue inhibitor is believed to play a rôle in limiting the growth of tissue in the adult animal.
DARK ADAPTATION IN DINEUTES
Authors: Clark Leonard B.
Published: May 2004

The level of dark adaptation of the whirligig beetle can be measured in terms of the threshold intensity calling forth a response.

The course of dark adaptation was determined at levels of light adaptation of 6.5, 91.6, and 6100 foot-candles. All data can be fitted by the same curve. This indicates that dark adaptation follows parts of the same course irrespective of the level of light adaptation. The intensity of the adapting light determines the level at which dark adaptation will begin.

The relation between log aI0 (instantaneous threshold) and log of adapting light intensity is linear over the range studied.
CRITICAL INTENSITY AND FLASH DURATION FOR RESPONSE TO FLICKER: WITH ANAX LARVAE
Authors: Crozier W. J. , Wolf E. , Zerrahn-Wolf G.
Published: May 2004

Determinations of the flicker response curve (F – log Im) with larvae of Anax junius (dragonfly) for various ratios tL/tD of light time to dark time in a flash cycle provide relations between tL/tD and the parameters of the probability integral fundamentally describing the F – log I function, including the variability of I. These relations are quantitatively of the same form as those found for this function in the sunfish, and are therefore non-specific. Their meaning for the theory of reaction to visual flicker is discussed. The asymmetry of the Anax curve, resulting from mechanical conditions affecting the reception of light by the arthropod eye, is (as predicted) reduced by relative lengthening of the fractional light time in a cycle.
EFFECTS OF POTASSIUM ON THE POTENTIAL OF HALICYSTIS
Authors: Osterhout W. J. V.
Published: May 2004

Sea water in which sodium has been replaced by potassium produces about the same degree of negativity in Halicystis and in Valonia.

With increasing dilution of this sea water up to 1 ÷ 16 the degree of negativity steadily falls off in Halicystis. This differs from the situation in Valonia where Damon finds that with increasing dilution the negativity passes through a minimum after which increasing dilution produces increasing negativity. But conditions in the two organisms differ so greatly that a comparison is of rather doubtful significance.
THE ACCUMULATION OF ELECTROLYTES
Authors: Jacques A. G.
Published: May 2004

Experiments on Valonia were carried out as follows:

Stage I.—Cells in dim light accumulated 0.08 M ammonia (NH3 + NH4OH + NH4+) from sea water containing 0.0025 M ammonia (but the concentration of undissociated ammonia appeared to remain less inside than outside). Potassium came out.

Stage II.—Cells in dim light in nearly ammonia-free normal sea water lost ammonia which was replaced by sodium entering from the sea water. Potassium in the sap remained practically constant.

Stage III.—The cells were placed in stronger light where the loss of ammonia continued and potassium entered. Sodium entered more rapidly than in Stage II.

Stage IV.—Cells transferred to sea water containing 0.0025 M ammonia again accumulated ammonia up to 0.1345 M.

The results in general harmonize with the view that the direction of movement of a base M through the protoplasm depends on the difference of the activity products (M)o(OH)o and (M)i(OH)i where the subscripts o and i refer to sea water and sap respectively.

On this basis, if the entrance of ammonia raised the internal concentration of OH sufficiently in Stage I potassium should come out in Stage I, as actually happened. The behavior of sodium is in doubt.

If the internal pH in Stage II were sufficiently high sodium should enter but not potassium. This was actually found.

In Stage III, if we suppose that the effect of stronger light is to increase the external pH (by photosynthesis) more than the internal pH (as found by Crozier) we can understand why potassium entered, because such an increase in pH could readily make the external value of (K) (OH) greater than the internal. This would also explain why sodium entered more rapidly than in Stage II.

When ammonia is coming out of the cell, sodium and potassium may enter more rapidly than usual without raising the internal concentration of halide above a certain critical value at which entrance appears to be checked.
LIMITING FACTORS IN PHOTOSYNTHESIS: LIGHT AND CARBON DIOXIDE
Authors: Smith Emil L.
Published: May 2004

1. Extensive measurements have been obtained (a) relating photosynthesis and light intensity for a large range of CO2 concentrations and (b) relating photosynthesis and CO2 at different light intensities. From these families of curves, the limiting factor relationship can be secured for any value of the photosynthesis rate.

2. In terms of previous work an equation has been derived for describing these relations between the intensity and CO2 concentration necessary to produce a definite amount of photosynthesis. This equation furnishes an exact description for all the data, except those for low rates of photosynthesis where a slightly different equation is required. The nature of the two equations suggests that a simple first order reaction determines the velocity of the light process at low photosynthesis rates, but that at high rates the mechanism is complicated by another factor.
KINETICS OF THE FORMATION OF PEPSIN FROM SWINE PEPSINOGEN AND IDENTIFICATION OF AN INTERMEDIATE COMPOUND
Authors: Herriott Roger M.
Published: May 2004

A study of the kinetics of the transformation of swine pepsinogen into pepsin under a variety of conditions has been made. The results show that the transformation as a whole is essentially autocatalytic in nature under all conditions.

Evidence is presented to show the existence of a compound intermediate between pepsinogen and pepsin. This compound was found to be a reversibly dissociable complex of pepsin and a low molecular weight inhibitor.

Some of the general properties of the intermediate compound and of the inhibitor have been examined.
THE VISIBILITY OF SINGLE LINES AT VARIOUS ILLUMINATIONS AND THE RETINAL BASIS OF VISUAL RESOLUTION
Authors: Hecht Selig , Mintz Esther U.
Published: May 2004

The visual resolution of a single opaque line against an evenly illuminated background has been studied over a large range of background brightness. It was found that the visual angle occupied by the thickness of the line when it is just resolved varies from about 10 minutes at the lowest illuminations to 0.5 second at the highest illuminations, a range of 1200 to 1.

The relation between background brightness and just resolvable visual angle shows two sections similar to those found in other visual functions; the data at low light intensities represent rod vision while those at the higher intensities represent cone vision. With violet light instead of white the two sections become even more clearly defined and separated.

The retinal image produced by the finest perceptible line at the highest brightness is not a sharp narrow shadow, but a thin broad shadow whose density distribution is described in terms of diffraction optics. The line of foveal cones occupying the center of this shadow suffers a decrease in the light intensity by very nearly 1 per cent in comparison either with the general retinal illumination or with that on the row of cones to either side of the central row. Since this percentage difference is near the limit of intensity discrimination by the retina, its retinal recognition is probably the limiting factor in the visual resolution of the line.

The resolution of a line at any light intensity may also be limited by the just recognizable intensity difference, because this percentage difference varies with the prevailing light intensity. As evidence for this it is found that the just resolvable visual angle varies with the light intensity in the same way that the power of intensity discrimination of the eye varies with light intensity.

It is possible that visual resolution of test objects like hooks and broken circles is determined by the recognition of intensity differences in their diffracted images, since the way in which their resolution varies with the light intensity is similar to the relation between intensity discrimination and light intensity.
ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON DURING ACTIVITY
Authors: Cole Kenneth S. , Curtis Howard J.
Published: May 2004

Alternating current impedance measurements have been made over a wide frequency range on the giant axon from the stellar nerve of the squid, Loligo pealii, during the passage of a nerve impulse. The transverse impedance was measured between narrow electrodes on either side of the axon with a Wheatstone bridge having an amplifier and cathode ray oscillograph for detector. When the bridge was balanced, the resting axon gave a narrow line on the oscillograph screen as a sweep circuit moved the spot across. As an impulse passed between impedance electrodes after the axon had been stimulated at one end, the oscillograph line first broadened into a band, indicating a bridge unbalance, and then narrowed down to balance during recovery. From measurements made during the passage of the impulse and appropriate analysis, it was found that the membrane phase angle was unchanged, the membrane capacity decreased about 2 per cent, while the membrane conductance fell from a resting value of 1000 ohm cm.2 to an average of 25 ohm cm.2

The onset of the resistance change occurs somewhat after the start of the monophasic action potential, but coincides quite closely with the point of inflection on the rising phase, where the membrane current reverses in direction, corresponding to a decrease in the membrane electromotive force. This E.M.F. and the conductance are closely associated properties of the membrane, and their sudden changes constitute, or are due to, the activity which is responsible for the all-or-none law and the initiation and propagation of the nerve impulse. These results correspond to those previously found for Nitella and lead us to expect similar phenomena in other nerve fibers.
INTRACELLULAR PHAGE PRECURSOR
Authors: Krueger A. P. , Scribner E. J.
Published: May 2004

1. Staphylococci activated by rapid growth in the presence of excess O2 and subsequently brought to a resting state by storage in Locke's solution at 5°C. produce a significant rise in [phage] when added to phage-containing solutions.

2. For satisfactory activation the staphylococci require a period of active growth in the presence of oxygen. Activation proceeds best on the acid side of neutrality although variation in pH from 5 to 9 has relatively little effect. Activated cells retain their phage-augmenting property for from 4 to 24 hours, and this property may be destroyed by heating the cells at temperatures which do not kill them. The critical thermal increment for heat inactivation is 90,000 suggesting that the reaction involves protein denaturation.

3. The reaction between activated cells and phage has the following characteristics:

A. It is complete in 1 to 2 minutes after mixing the reactants.

B. The increase in phage does not depend upon bacterial growth nor does it involve any untoward effect on the titration system.

C. Serum prepared by injecting rabbits with normal live staphylococci or with activated staphylococci when mixed with activated cells before the addition of phage will prevent the customary increase in [phage].

4. The phage-producing reaction which follows the addition of activated cells to phage can be interpreted in terms of the precursor theory. It is likely that the precursor either is a protein or contains a protein as an essential component.

5. There is no way of deciding at present whether the reaction between phage and precursor represents the hydrolytic cleavage of a protein or whether it is the final step in a synthesis catalyzed by phage.
THE FLICKER RESPONSE CONTOUR FOR THE FROG
Authors: Crozier W. J. , Wolf Ernst
Published: May 2004

The flicker response contour for the frog Rana pipiens exhibits the duplex character typical for most vertebrates. By comparison (under the same conditions of temperature, 21.5°, and light-time fraction, = 0.5), the low intensity section of the F - log I curve is the smallest thus far found.

The cone portion of the curve is satisfactorily described by a probability integral. The rod part represents the addition of a small group of sensory effects upon the lower end of the cone curve, from which it can be analytically separated.

The relation between the two groups of sensory effects permits certain tests of the rule according to which (in homogeneous data) Im and σ1I1 are in direct proportion.
PHYSICOCHEMICAL PROPERTIES OF THE PROTEOLYTIC ENZYME FROM THE LATEX OF THE MILKWEED, ASCLEPIAS SPECIOSA TORR. SOME COMPARISONS WITH OTHER PROTEASES
Authors: Winnick Theodore , Davis Alva R. , Greenberg David M.
Published: May 2004

1. The rates of heat inactivation of papain, bromelin, and asclepain were determined at several different temperatures. Papain was by far the most resistant to heat.

2. The destruction of papain at 75–83° and bromelin at 55–70° followed the course of a first order reaction, except that for longer times of heating, bromelin (at 60–70°) was inactivated more rapidly than the first order equation required.

3. The rate of inactivation of asclepain at 55–70° followed the second order equation.

4. The critical thermal increments of inactivation of papain and bromelin, calculated with the van't Hoff-Arrhenius equation, were of the same high order that has been found for protein denaturation. The increment for asclepain was somewhat lower.
STABILIZATION OF SPIDER CRAB NERVE MEMBRANES BY ALKALINE EARTHS, AS MANIFESTED IN RESTING POTENTIAL MEASUREMENTS
Authors: Guttman Rita
Published: May 2004

1. The alkaline earths, Ba, Sr, Ca, and Mg, in isotonic solutions of their chlorides, have, in general, no effect upon the resting potential of non-medullated spider crab nerve.

2. Ba, Sr, and Ca can, however, prevent the depressing action of K upon the resting potential. The order of effectiveness of these ions in this regard is the following: Ba > Sr > Ca.

3. Ba, Sr, Ca, and Mg oppose the depressing action of veratrine sulfate upon the resting potential. The order of effectiveness is Ba > Sr > Ca > Mg. The relation between drop in potential caused by veratrine sulfate and the logarithm of the veratrine sulfate concentration is a linear one.

4. The action of various other organic ions and molecules which depress the resting potential: saponin, amyl urethane, chloral hydrate, and Na salicylate is neutralized by Ba.

5. Hypertonic sea water solutions do not affect the resting potential. Also, preliminary experiments indicate that the nerves do not shrink in hypertonic solutions although they swell in hypotonic sea water.

6. The alkaline earths depress excitability reversibly. The various organic agents which depress the resting potential also depress excitability, in most cases, reversibly, but the concentrations necessary to depress excitability are much smaller than those necessary to depress the resting potential.

7. The relation of these findings to theories put forward as possible explanations of resting potential phenomena is considered.
SOLUBILITY STUDIES ON PURIFIED TOBACCO MOSAIC VIRUS
Authors: Loring Hubert S.
Published: May 2004

Different samples of purified tobacco mosaic virus show a relatively wide variation in solubility in ammonium sulfate solution. This variation and the type of solubility curve obtained in the presence of varying amounts of solid phase show that the purified virus whether isolated by mild treatment with ammonium sulfate or by ultracentrifugation is not a homogeneous chemical substance but contains more soluble and less soluble virus fractions of comparable specific activities. Long contact with strong ammonium sulfate solutions or 0.1 M phosphate buffer results in a decrease in solubility. The variation in the solubility of samples isolated from different plants by the same method seems to depend in part on the length of time the plants are inoculated before they are cut, and probably also on the conditions under which they are grown. Virus preparations isolated from plants of different genera grown under the same conditions and inoculated at the same time, however, behaved like identical substances in solubility experiments.
THE RÔLE OF ORGANIC SUBSTRATES IN PHOTOSYNTHESIS OF PURPLE BACTERIA
Authors: Foster Jackson W.
Published: May 2004

A representative of the photosynthetic non-sulfur purple bacteria (Athiorhodaceae) capable of using simple alcohols has been isolated in pure culture.

By means of quantitative analysis of cultures at different stages of development it has been shown that this organism converts isopropanol quantitatively into acetone, simultaneously reducing CO2 in the light. The data can be represented by the equation

2 CH3CHOHCH3 + CO2 → 2 CH3COCH3 + (CH2O) + H2O.

Manometric experiments with suspensions of resting cells have fully corroborated the results obtained with growing cultures.

The experiments have conclusively proved that an organic substrate may fulfill exclusively the function of hydrogen donor for the photochemical CO2-reduction in purple bacteria photosynthesis.
THE ELECTRICAL CAPACITY OF VALONIA
Authors: Blinks L. R. , Skow R. K.
Published: May 2004

Impaled cells of Valonia were balanced in a Wheatstone bridge against a simple series-parallel circuit of two resistances and a capacity, the transient charge and discharge curves at make and break of direct current being recorded with a string galvanometer. With the resistances properly balanced, a series of characteristic deflections resulted when the balancing capacity was varied. With many cells, no complete capacity balance was ever attained over the entire transient time course; but instead either a monophasic or diphasic residual deflection always remained. This behavior is comparable to that of a polarizing electrode in D.C., although not so clearly marked; and it is concluded that Valonia usually has an appreciable polarization component, probably in parallel with a static capacity.

However, some cells can be balanced almost completely against a mica condenser of proper value, which indicates that they display a nearly pure static capacity under some conditions. This static state could be produced experimentally by exposure to weak acids (acetic, carbonic, etc.) and by metabolic agents probably inducing internal acidity (low oxygen tension, long exposure to cold, narcotics, etc.). Conversely, penetrating weak bases, such as ammonia, abolished the static capacity, or even any regular polarization. Light acts something like ammonia, after an initial "acid gush" anomaly. Most of these agents likewise affect the P.D. and its response to external ionic alterations, and it seems likely that the change in capacity type reflects altered ionic permeabilities and relative mobilities.
ON THE RELATION BETWEEN GROWTH AND RESPIRATION IN THE AVENA COLEOPTILE
Authors: Commoner Barry , Thimann Kenneth V.
Published: May 2004

1. The growth of Avena coleoptile sections in sucrose and auxin solutions is inhibited by various substances which are known to act as dehydrogenase inhibitors.

2. Iodoacetate, which is particularly active in this connection, inhibits all growth at a concentration of 5 x 10–5 M, but produces only a slight inhibition of oxygen uptake.

3. The growth inhibition by iodoacetate is completely removed by malate and fumarate, and to a lesser extent by succinate and pyruvate.

4. These acids themselves increase the effect of auxin on growth and also increase the respiration of the coleoptile sections, but only if auxin is present.

5. When sections have been soaked in malate or fumarate, the addition of auxin considerably increases the total respiration. Further, the concentration range over which this increase takes place parallels that active in promoting growth.

6. The four-carbon acids provide a respiratory system which is part of the chain of growth processes, and which is in some way catalyzed by auxin. It represents a small but variable fraction of the total respiration.
A NEW FORM OF DIFFRACTOMETER
Authors: Cox Richard T. , Ponder Eric
Published: May 2004

A simple diffractometer is described, in which monochromatic light is focused on a pinhole, rendered parallel, and passed through a film of red cells or other objects the size of which is sought. The diffraction patterns are photographed on special plates, and the positions of the first minimum and of the first maximum are subsequently found by the use of a simplified microphotometer. The method gives substantially the same results for red cell radius and (calculated) volume as do other standard methods.