bluuebunny/crossref_metadata_2025 huggingface dataset:
INTENSITY AND CRITICAL FREQUENCY FOR VISUAL FLICKER
Authors: Crozier W. J. , Wolf E. , Zerrahn-Wolf G.
Published: May 2004

Using the rotating striped cylinder device previously employed for determination of the flicker response function with lower animals, corresponding measurements have been made with human observers. The curves based upon the relation between critical flash frequency and critical intensity for the signalling of the recognition of flicker have the properties of human flicker fusion data as obtained by other methods. They also have the quantitative properties of the flicker curves provided by the motor responses of insects and fishes to the seen movement of flashes. This applies to the variation found in repeated measurements as well as to the nature of the analytical function describing the connection between flash frequency and intensity. The data for human visual flicker and those for the responses of lower animals are therefore essentially homologous.
CRITICAL ILLUMINATION FOR RESPONSE TO FLICKERED LIGHT, WITH DRAGONFLY LARVAE (ANAX), IN RELATION TO AREA OF EYE
Authors: Crozier W. J. , Wolf E. , Zerrahn-Wolf G.
Published: May 2004

Arthropods with large convex eyes provide curves of critical illumination for response as a function of flicker frequency (or of visual acuity) which depart from the probability integral type characteristically found for F – log I with vertebrates. By means of experiments with Anax nymphs in which various parts of the eye have been opaqued it is shown that the special shape of the flicker curve is due to the mechanical disadvantage of the periphery of the eye in the reception of light, which is overcome by higher intensities. It is not due to a fixed spatial pattern of intrinsic individual excitabilities of the ommatidia.

Reduction of retinal area decreases Fmax., and increases log I for F/Fmax. = 50 per cent. The direct proportionality of Im to P.E.1I is independent of area. Certain relations of these facts to the theory of response to flicker have been discussed.
CONCENTRATION AND PURIFICATION OF BACTERIOPHAGE
Authors: Northrop John H.
Published: May 2004

1. A method for isolating a nucleoprotein from lysed staphylococci culture is described.

2. It is homogeneous in the ultracentrifuge and has a sedimentation constant of 650 x 10–13 cm. dyne–1 sec.–1, corresponding to a molecular weight of about 300,000,000.

3. The diffusion coefficient varies from about 0.001 cm.2/day in solutions containing more than 0.1 mg. protein/ml. to 0.02 in solutions containing less than 0.001 mg. protein/ml. The rate of sedimentation also decreases as the concentration decreases. It is suggested, therefore, that this protein exists in various sized molecules of from 500,000–300,000,000 molecular weight, the proportion of small molecules increasing as the concentration decreases.

4. This protein is very unstable and is denatured by acidity greater than pH 5.0, by temperature over 50°C. for 5 minutes. It is digested by chymo-trypsin but not by trypsin.

5. The loss in activity by heat, acid, and chymo-trypsin digestion is roughly proportional to the amount of denatured protein formed under these conditions.

6. The rate of diffusion of the protein is the same as that of the active agent.

7. The rate of sedimentation of the protein is the same as that of the active agent.

8. The loss in activity when susceptible living or dead bacteria are added to a solution of the protein is proportional to the loss in protein from the solution. Non-susceptible bacteria remove neither protein nor activity.

9. The relative ultraviolet light absorption, as determined directly, agrees with that calculated from Gates' inactivation experiments in the range of 2500–3000 Å. u. but is somewhat greater in the range of 2000–2500 Å. u.

10. Solubility determinations showed that most of the preparations contained at least two proteins, one being probably the denatured form of the other. Two preparations were obtained, however, which had about twice the specific activity of the earlier ones and which gave a solubility curve approximating that of a pure substance.

11. It is suggested that the formation of phage may be more simply explained by analogy with the autocatalytic formation of pepsin and trypsin than by analogy with the far more complicated system of living organisms.
AN ULTRACENTRIFUGAL ANALYSIS OF CONCENTRATED STAPHYLOCOCCUS BACTERIOPHAGE PREPARATIONS
Authors: Wyckoff Ralph W. G.
Published: May 2004

Analytical observations have been made with the air ultracentrifuge on concentrated staphylococcus bacteriophage solutions and on these solutions inactivated by alkali, chymo-trypsin, and heat.

All active solutions contain a homogeneous heavy component that sediments with a constant of s20° = ca. 650 x 10–13 cm. sec.–1 dynes–1, has an apparent density of ca. 1.20, and a molecular weight probably not less than 200 millions. There is also present some very light ultraviolet-absorbing material which is not a carrier of bacteriophage activity. The amount of the heavy component is not strictly proportional to the bacteriophage activity so that if the activity resides in it, as appears to be the case, inactivation may occur without measurable change in molecular size and shape.

When the bacteriophage solutions are inactivated by chymo-trypsin, the heavy component is not disrupted but the sedimenting boundaries have always been fairly diffuse. As the activity gradually disappears from alkaline solutions, the heavy component is replaced by unsedimentable material. When a solution is inactivated by heating, a dilute gel is produced which sediments with an exceptionally sharp boundary in a relatively intense centrifugal field,
THE EFFECT OF AUXINS ON PROTOPLASMIC STREAMING. II
Authors: Sweeney Beatrice Marcy , Thimann Kenneth V.
Published: May 2004

1. A further study has been made of the effect of indole-3-acetic acid (auxin) on protoplasmic streaming in the epidermal cells of the Avena coleoptile.

2. The transient nature of the effect of auxin, both in accelerating and retarding streaming, is due to the temporary exhaustion of carbohydrate from the tissues. In presence of 1 per cent fructose or some other sugars the acceleration or retardation of streaming by auxin is not transient, but is maintained for at least 2 hours.

3. The retardation of streaming brought about by concentrations of auxin above 0.5 mg. per liter is due to oxygen deficiency This has been confirmed in several ways.

4. It follows that the effect of auxin is to increase the respiration of the coleoptile tissue.

5. Younger coleoptiles, 3 cm. long, are sensitive to lower concentrations of auxin than those 5 cm. long, and more readily exhibit oxygen deficiency as a result of the action of auxin. However, after decapitation their response to auxin more closely resembles that of 5 cm. coleoptiles.

6. The retardation of streaming in such coleoptiles, resulting from oxygen deficiency, is delayed by very dilute solutions of histidine. On this basis an explanation is suggested for the results of Fitting on streaming in Vallisneria leaves.

7. The mean rate of streaming in control untreated coleoptiles in pure water varies with the time of year, but not with the time of day.

8. The results support the view that auxin accelerates an oxygen-consuming process which controls the rate of protoplasmic streaming, and that the latter controls growth. The substrate for this process is probably sugar.

9. It is suggested that auxin also accelerates another oxygen-consuming process, which may withdraw oxygen from the process which controls streaming rate and hence cause retardation of the latter.
TRANSFORMATION OF SWINE PEPSINOGEN INTO SWINE PEPSIN BY CHICKEN PEPSIN
Authors: Herriott Roger M. , Bartz Quentin R. , Northrop John H.
Published: May 2004

Activation of swine pepsinogen with chicken pepsin results in the formation of swine pepsin.

Activation of chicken pepsinogen with swine pepsin results in the formation of chicken pepsin.

The structure responsible for the species specificity of the enzyme is therefore present in the inactive precursor.
ELECTRIC IMPEDANCE OF SINGLE MARINE EGGS
Authors: Cole Kenneth S. , Curtis Howard J.
Published: May 2004

Alternating current impedance measurements have been made on several single marine eggs over the frequency range from 1 to 2500 kilocycles per second. The eggs were placed in the center of a short capillary made by heating the end of a 2 mm. thin walled glass tube until it nearly closed, and electrodes were placed in the sea water on each side of the egg.

When it is assumed that the membrane conductance is negligible, the membrane capacity and internal resistances of unfertilized and fertilized Arbacia eggs agree with the values obtained from suspensions. Preliminary data on centrifugally separated half Arbacia eggs, and whole Cumingia and Chaetopterus eggs are given.
FORMATION OF TRYPSIN FROM TRYPSINOGEN BY AN ENZYME PRODUCED BY A MOLD OF THE GENUS PENICILLIUM
Authors: Kunitz M.
Published: May 2004

1. A powerful kinase which changes trypsinogen to trypsin was found to be present in the synthetic liquid culture medium of a mold of the genus Penicillium.

2. The concentration of kinase in the medium is increased gradually during the growth of the mold organism and continues to increase for some time even after the mold has ceased growing.

3. Mold kinase transforms trypsinogen to trypsin only in an acid medium. It differs thus from enterokinase and trypsin which activate trypsinogen best in a slightly alkaline medium.

4. The action of the mold kinase in the process of transformation of trypsinogen is that of a typical enzyme. The process follows the course of a catalytic unimolecular reaction, the rate of formation of a definite amount of trypsin being proportional to the concentration of kinase added. The ultimate amount of trypsin formed, however, is independent of the concentration of kinase used.

5. The formation of trypsin from trypsinogen by mold kinase is not accompanied by any measurable loss of protein.

6. The temperature coefficient of formation of trypsin from trypsinogen by mold kinase varies from Q5–15 = 1.70 to Q25–30 = 1.25 with a corresponding variation in the value of µ from 8100 to 4250.

7. Trypsin formed from trypsinogen by means of mold kinase is identical in crystalline form with the crystalline trypsin obtained by spontaneous autocatalytic activation of trypsinogen at pH 8.0. The two products have within the experimental error the same solubility and specific activity. A solution saturated with the crystals of either one of the trypsin preparations does not show any increase in protein concentration or activity when crystals of the other trypsin preparation are added.

8. The Penicillium mold kinase has a slight activating effect on chymo-trypsinogen the rate being only 1–2 per cent of that of trypsinogen. The activation, as in the case of trypsinogen, takes place only in an acid medium.

9. Mold kinase is rapidly destroyed when brought to pH 6.5 or higher, and also when heated to 70°C. In the temperature range of 50–60°C. the inactivation of kinase follows a unimolecular course with a temperature coefficient of Q10 = 12.1 and µ = 53,500. The molecular weight of mold kinase, as determined by diffusion, is 40,000.
BRIGHTNESS DISCRIMINATION AS A FUNCTION OF THE DURATION OF THE INCREMENT IN INTENSITY
Authors: Graham C. H. , Kemp E. H.
Published: May 2004

1. This investigation has been concerned with an analysis of brightness discrimination as it is influenced by the duration of ΔI. The durations used extend from 0.002 second to 0.5 second.

2. ΔI/I values at constant intensity are highest for the shortest duration and decrease with an increase in duration up to the limits of a critical exposure time. At durations longer than the critical duration the ratio ΔI/I remains constant.

3. The Bunsen-Roscoe law holds for the photolysis due to ΔI. This is shown by the fact that, within the limits of a critical duration, the product of ΔI and exposure time is constant for any value of prevailing intensity, I.

4. At durations greater than the critical duration the Bunsen-Roscoe law is superseded by the relation ΔI = Constant. This change of relation is considered in the light of Hartline's discussion (1934).

5. The critical duration is a function of intensity. As intensity increases the critical duration decreases.

6. Hecht's theory (1935) accounts for the data of this experiment if it be assumed that brightness discrimination is determined by a constant amount of photolysis.
CHANGES OF APPARENT IONIC MOBILITIES IN PROTOPLASM
Authors: Osterhout W. J. V.
Published: May 2004

Lowering the pH of sea water from 8.2 to 6.4 lowers the positive P.D. of Halicystis reversibly (this does not happen with Valonia).

Exposure to sea water at pH 6.4 does not affect the apparent mobility of Na+ or of K+ (this agrees with Valonia).

Guaiacol makes the P.D. of Halicystis less positive (in Valonia it has the opposite effect).

Exposure to guaiacol does not reverse the effect of KCl in Halicystis which in this respect differs from Valonia.

The P.D. can be changed from 66 mv. positive to 23 mv. negative by the combined action of KCl and guaiacol.

Exposure to guaiacol affects Halicystis and Valonia similarly in respect to their behavior with dilute sea water. Normally the dilute sea water makes the P.D. more negative but after sufficient exposure to guaiacol dilute sea water either produces no change in P.D. or makes it more positive. In the latter case we may assume that the apparent mobility of Na+ has become greater than that of Cl- as the result of the action of guaiacol. (Normally the apparent mobility of Cl- is greater than that of Na+.)

In Halicystis, as in Valonia and in Nitella, an organic substance can greatly change the apparent mobilities of certain inorganic ions (K+ or Na+).
FACTORS LIMITING BACTERIAL GROWTH
Authors: Hershey A. D. , Bronfenbrenner J.
Published: May 2004

1. Measurements of the rate of oxygen uptake per cell in transplants of Bacterium coli from cultures of this organism in different phases of growth have given results in essential agreement with the observations of others.

2. Correlations of viable count, centrifugable nitrogen, and turbidity, with oxygen consumption, indicate that the increased metabolism during the early portion of the growth period is quantitatively referable to increased average size of cells.

3. Indirect evidence has suggested that the initial rate of growth of transplants is not related to the phase of growth of the parent culture.
ELECTROKINETIC PHENOMENA
Authors: Abramson Harold A. , Moyer Laurence S.
Published: May 2004

1. Although the isoelectric points of dissolved cystine, tyrosine, and aspartic acid molecules lie at widely differing pH values, the isoelectric points of the surfaces of these substances in the crystalline state are all near pH 2.3. This was found to be true in solutions of hydrochloric acid and in acetate buffers of approximately constant ionic strength.

2. When suspended in gelatin, tyrosine and cystine crystals adsorb the protein and attain a surface identical in behavior with gelatin-coated quartz or collodion particles.

3. Aluminum ions at low concentrations reduce the electric mobilities of tyrosine crystals to zero in a manner analogous to their effect on other surfaces.

4. Alkyl benzene droplets also have their electric mobility reduced to zero at low pH values but, unlike the amino acids, a change in sign was never noticed.

5. The mobility of tyrosine crystals is independent of crystal length between 2–100µ. Below this size the mobilities are decreased.

6. These results are discussed in connection with the concept of the general definition of the isoelectric point and the behavior of certain insoluble proteins such as wool and silk fibroin.
TRANSVERSE ELECTRIC IMPEDANCE OF THE SQUID GIANT AXON
Authors: Curtis Howard J. , Cole Kenneth S.
Published: May 2004

The impedance of the excised giant axon from hindmost stellar nerve of Loligo pealii has been measured over the frequency range from 1 to 2500 kilocycles per second. The measurements have been made with the current flow perpendicular to the axis of the axon to permit a relatively simple analysis of the data. It has been found that the axon membrane has a polarization impedance with an average phase angle of 76° and an average capacity of 1.1µf./cm2 at 1 kilocycle. The direct current resistance of the membrane could not be measured, but was greater than 3 ohm cm.2 and the average internal specific resistance was four times that of sea water. There was no detectable change in the membrane impedance when the axon lost excitability, but some time later it decreased to zero.
THE ACCUMULATION OF ELECTROLYTES
Authors: Jacques A. G. , Osterhout W. J. V.
Published: May 2004

The nitrate concentration in the sap of Valonia macrophysa, Kütz., is at least 2000 times that of the sea water, and in Halicystis Osterhoutii, Blinks and Blinks, at least 500 times that of the sea water.
EXCITATION OF NERVE FIBERS IN THE SQUID (LOLIGO PEALII)
Authors: Prosser C. Ladd , Chambers Alfred H.
Published: May 2004

1. Strength-duration data for the giant fiber of the great stellar nerve of the squid (Loligo pealii) can be approximately described by several mathematical formulations.

2. Excitation time constants for isolated giant fibers are essentially the same as constants of the giant fibers in the intact nerve.

3. The strength-duration curves of the fibers in the intact nerve lie higher on the voltage axis than those of the isolated fibers. It is concluded that the principal effect of other fibers upon the excitation of one fiber in a nerve trunk is that of shunting the stimulating current.

4. Deterioration of the nerve shifts the curve upward and to the left, resulting in shorter time constants.

5. Decreasing interelectrode distance also shifts the curve upward and to the left.

6. Excitation time constants of the giant fibers are larger with plate electrodes than with wire or pore electrodes.

7. The strength-duration curves of the smaller fin nerve fibers lie consistently to the right of, and the time constants are longer than those of the giant fibers.
PACEMAKERS IN NITELLA
Authors: Osterhout W. J. V. , Hill S. E.
Published: May 2004

Many forms of irregular rhythm and of partial block occurring in the vertebrate heart can be duplicated in Nitella.

In order to observe these phenomena the cells of Nitella are kept for 6 weeks or more in a nutrient solution. They are then exposed for 3 hours or less to 0.01 M NaCl, NaSCN, or guanidine chloride, which reduce the time required for the action current to about 1 second (the normal time is 15 to 30 seconds).

A pacemaker is established at one end of the cell by placing it in contact with 0.01 M KCl. This produces action currents at the rate of about 1 a second. Apparently some parts of the cell are unable to follow this rapid pace and hence fall into irregular rhythms (arrhythmia) and fail to register all the impulses (partial block).
EFFECT OF SODIUM SULFATE ON THE PHAGE-BACTERIUM REACTION
Authors: Krueger A. P. , Strietmann W. L.
Published: May 2004

Bacteriophagy taking place in the presence of M/8 Na2SO4 has the following pronounced characteristics:

A. Time of lysis is considerably prolonged.

B. The bacteria take up less than the normal amount of phage.

C. Phage production occurs at one-third the customary rate.

D. It takes four times as much phage to lyse a Na2SO4-treated bacterium than a normal one.

E. Bacterial growth is not affected by Na2SO4.

The lag phase and the lowered rate of phage production can be attributed to the Na2SO4 effect on the cell surface. Less phage is taken up by the cells and contact of phage with the bacterium's precursor-producing mechanism is impeded.
CALCULATIONS OF BIOELECTRIC POTENTIALS
Authors: Osterhout W. J. V. , Hill S. E.
Published: May 2004

In Nitella the substitution of KCl for NaCl changes the P.D. in a negative direction. In some cases this change is lessened by adding solid CaCl2 to the solution of KCl. This may be due to lessening the partition coefficient of KCl or to decreasing the solubility of an organic substance which sensitizes the cell to the action of KCl.

Little or no correlation exists between this effect of calcium and its ordinary antagonistic action in producing a balanced solution which preserves the life of the cell indefinitely.

CaCl2 is negative to NaCl but positive to KCl.

The effects of mixtures of KCl, NaCl, and CaCl2 are discussed. The concentration effect of a mixture of KCl + CaCl2 shows certain peculiarities due to action currents: these resemble those found with pure KCl.

These studies and others on Nitella, Valonia, and Halicystis indicate that mobilities and partition coefficients are variable and can be brought under experimental control.
BIOELECTRIC POTENTIALS IN HALICYSTIS
Authors: Blinks L. R. , Darsie M. L. , Skow R. K.
Published: May 2004

The potential difference across the protoplasm of impaled cells of Halicystis is not affected by increase of oxygen tension in equilibrium with the sea water, nor with decrease down to about 1/10 its tension in the air (2 per cent O2 in N2). When bubbling of 2 per cent O2 is stopped, the P.D. drifts downward, to be restored on stirring the sea water, or rebubbling the gas. Bubbling 0.2 per cent O2 causes the P.D. to drop to 20 mv. or less; 1.1 per cent O2 to about 50 mv. Restoration of 2 per cent or higher O2 causes recovery to 70 or 80 mv. often with a preliminary cusp which decreases the P.D. before it rises. Perfusion of aerated sea water through the vacuole is just as effective in restoring the P.D. as external aeration, indicating that the direction of the oxygen gradient is not significant.

Low O2 tension also inhibits the reversed, negative P.D. produced by adding NH4Cl to sea water, 0.2 per cent O2 bringing this P.D. back to the same low positive values found without ammonia. Restoration of 2 per cent O2 or air, restores this latent negativity. At slightly below the threshold for ammonia reversal, low O2 may induce a temporary negativity when first bubbled, and a negative cusp may occur on aeration before positive P.D. is regained. This may be due to a decreased consumption of ammonia, or to intermediate pH changes.

The locus of the P.D. alteration was tested by applying increased KCl concentrations to the cell exterior; the large cusps produced in aerated solutions become greatly decreased when the P.D. has fallen in 0.2 per cent O2. This indicates that the originally high relative mobility or concentration of K+ ion has approached that of Na+ in the external protoplasmic surface under reduced O2 tension. Results obtained with sulfate sea water indicate that Na+ mobility approaches that of SO4— in 0.2 per cent O2. P.D. measurements alone cannot tell whether this is due to an increase of the slower ion or a decrease of the faster ion. A decrease of all ionic permeability is indicated, however, by a greatly increased effective resistance to direct current during low O2. Low resistance is regained on aeration.

The resistance increase resembles that produced by weak acids, cresol, etc. Acids or other substances produced in anaerobiosis may be responsible for the alteration. Or a deficiency of some surface constituent may develop.

In addition to the surface changes there may be alterations in gradients of inorganic or organic ions within the protoplasm, but there is at present no evidence on this point. The surface changes are probably sufficient to account for the phenomena.
THEORY AND MEASUREMENT OF VISUAL MECHANISMS
Authors: Crozier W. J. , Holway A. H.
Published: May 2004

Monocular threshold stimulus intensities (ΔIo, photons) were measured along the 0–180° meridian of human retinae for three observers. The test image was small (= 0.08°) and of short duration (= 0.20 second). ΔIo was found to decrease as the angular distance from the fovea was increased. Actual counts of the number of retinal elements per mm.2 along the 0–180° meridian (Østerberg) were compared with the obtained results. No direct correlation was found to exist between visual sensitivity and the number of retinal elements.

Binocular threshold stimuli were also measured along the same meridian. The form of the function relating binocular visual sensitivity and retinal position was discovered to be essentially similar to that for monocular sensitivity, but is more symmetrical about the center of the fovea. The magnitude of the binocular measurement is in each case smaller than that of the monocular threshold stimulus intensity for the more sensitive eye. The ratio is statistically equal to 1.4 (a fact which suggests Piper's rule).

These results are shown to be consistent with the hypothesis that the process critical for the eventuation of the threshold response is localized in the central nervous system. They are not consistent with the view that the quantitative properties of visual data are directly determined by properties of the peripheral retina.
THE ANTAGONISM BETWEEN SODIUM AND MAGNESIUM IONS IN THEIR ACTION UPON OXALATE ION
Authors: Greenwald Isidor
Published: May 2004

The action of NaCl upon the effect of MgCl2 upon oxalate buffer systems, interpreted by Simms as an instance of antagonism of Na+ and Mg++, has been shown to be capable of formulation as the effect of increasing ionic strength upon the dissociation of MgC2O4 into magnesium and oxalate ions.
PURIFICATION AND CONCENTRATION OF ENTEROKINASE
Authors: Kunitz M.
Published: May 2004

A concentrated solution of purified enterokinase is conveniently prepared from the fluid contents of pigs' duodena by means of fractional precipitation with ammonium sulfate under the proper pH conditions.
THE FLICKER RESPONSE CONTOURS FOR GENETICALLY RELATED FISHES. II
Authors: Crozier W. J. , Wolf Ernst
Published: May 2004

The flicker response contour has been determined for several species and types of the teleosts Xiphophorus (X.) and Platypoecilius (P.) under the same conditions. The curve (F vs. log Im) is the same for representatives of each generic type, but is different for the two genera. Its duplex nature is analyzable in each instance by application of the probability integral equation to the rod and cone constituent parts. The parameters of this function provide rational measures of invariant properties of the curves, which have specific values according to the genetic constitution of the animal. The F1 hybrids (H'') of X. montezuma x P. variatus show dominance of the X. properties with respect to cone Fmax. and σ' log I, but an intermediate value of the abscissa of inflection (τ'). The rod segment shows dominance of σ' log I from P., but an intermediate value of Fmax. and of τ'. The composite flicker curve involves the operation of two distinct assemblages of excitable elements, differing quantitatively but not qualitatively in physicochemical organization, probably only secondarily related to the histological differentiation of rods and cones because almost certainly of central nervous locus, but following different rules in hereditary determination, and therefore necessarily different in physical organization. The interpretation of the diverse behavior of the three parameters of the probability summation is discussed, particularly in relation to the physical significance of these parameters as revealed by their quantitative relations to temperature, retinal area, and light time fraction in the flash cycle, and to their interrelations in producing the decline of rod effects at higher intensities.

It is stressed that in general the properties of the parameters of a chosen interpretive analytical function must be shown experimentally to possess the physical properties implied by the equation selected before the equation can be regarded as describing those invariant properties of the organic system concerned upon which alone can deduction of the nature of the system proceed. The importance of genetic procedures in furthering demonstration that the biological performance considered in any particular case exhibits constitutionally invariant features provides a potentially powerful instrument in such rational analysis.
TEMPERATURE AND CRITICAL ILLUMINATION FOR REACTION TO FLICKERING LIGHT
Authors: Crozier W. J. , Wolf Ernst
Published: May 2004

For the sunfish Enneacanthus the mean value of the critical illumination for response to visual flicker at constant flash frequency (with light time = dark time) is related to temperature by the Arrhenius equation. The temperature characteristic for 1/Im is different above and below 20°C. In each range (12° to 20°; 20° to 30°) the temperature characteristic is the same for rod and cone segments of the duplex flicker response contour: 8,200 and 14,400. This makes it difficult, if not impossible, to consider that the two groups of elements are organized in a significantly different way chemically. For the presumptively rod-connected elements implicated in response to flicker, the curve is markedly discontinuous, so that the high and low temperature parts are dislocated; whereas for the cones they are not. This is entirely consistent with other (e.g., genetic) evidence pointing to their separate physical substrata.

The uncommon exhibition of a higher µ over a higher range of temperature, previously found, however, in a few cases, together with the different relations of rod and cone effects to the critical temperature, explain aspects of these data which in earlier incomplete measurements were found to be puzzling.
THE KINETICS OF PENETRATION
Authors: Jacques A. G.
Published: May 2004

The accumulation of ammonia takes place more rapidly in light than in darkness. The accumulation appears to go on until a steady state is attained. The steady state concentration of ammonia in the sap is about twice as great in light as in darkness. Both effects are possibly due to the fact that the external pH (and hence the concentration of undissociated ammonia) outside is raised by photosynthesis.

Certain "permeability constants" have been calculated. These indicate that the rate is proportional to the concentration gradient across the protoplasm of NH4X which is formed by the interaction of NH3 or NH4OH and HX, an acid elaborated in the protoplasm. The results are interpreted to mean that HX is produced only at the sap-protoplasm interface and that on the average its concentration there is about 7 times as great as at the sea water-protoplasm interface. This ratio of HX at the two surfaces also explains why the concentration of undissociated ammonia in the steady state is about 7 times as great in the sea water as in the sap. The permeability constant P''' appears to be greater in the dark. This is possibly associated with an increase in the concentration of HX at both interfaces, the ratio at the two surfaces, however, remaining about the same.

The pH of sap has been determined by a new method which avoids the loss of gas (CO2), an important source of error. The results indicate that the pH rises during accumulation but the extent of this rise is smaller than has hitherto been supposed.

As in previous experiments, the entering ammonia displaced a practically equivalent amount of potassium from the sap and the sodium concentration remained fairly constant.

It seems probable that the pH increase is due to the entrance of small amounts of NH3 or NH4OH in excess of the potassium lost as a base.
THE ELECTROPHORETIC MOBILITY OF RABBIT ERYTHROCYTES AND GHOSTS
Authors: Abramson Harold A. , Furchgott Robert F. , Ponder Eric
Published: May 2004

Measurements of the electrical mobility of washed rabbit red cells and of ghosts produced by hypotonic solutions, freezing-and-thawing, chloroform, and saponin were made in the Abramson horizontal microelectrophoresis cell. These different forms of lysis, which corresponds to a variety of degrees of injury to the red cell, are unaccompanied by any change in electrical mobility. These observations are discussed from the standpoint of the possible structure of the cell membrane and the action of lysins upon it.
THE FLICKER RESPONSE CONTOUR FOR THE GECKO (ROD RETINA)
Authors: Crozier W. J. , Wolf Ernst
Published: May 2004

The flicker response contour for the gecko Sphaerodactylus (retina with only rods) agrees in all essential respects (intensity range, shape) with that for the turtle Pseudemys (cone retina), as determined under equivalent conditions with the same apparatus. With experimentally determined correction for the expansion of the iris at the very lowest intensities, the F - log I contour for the gecko is a simple probability integral. Its maximum F is lower than that for other animals; this means simply a smaller number of available sensory elements. The quantitative parallelism in the magnitudes of the intensities at the inflection of F - log I and the shape constants for rod and cone animals show that assumptions from comparative histological evidence concerning the properties of rods and cones in relation to visual performance may be quite misleading.
THE ELECTRICAL IMPEDANCE OF MUSCLE DURING THE ACTION OF NARCOTICS AND OTHER AGENTS
Authors: Guttman Rita
Published: May 2004

1. The effect of certain inorganic cations upon the electrical impedance of the sartorius muscle of the frog was investigated. While Na, K, and Mg have little effect upon the resistance of muscle, Ba and Ca cause it to fall. The use of physiologically "unbalanced" salt solution does not in itself seem to affect muscle impedance.

2. The time course of the effect upon muscle impedance of the penetration of substances into the intercellular spaces was studied by treating the muscle with sugar solutions. Half of the effect is over in three-quarters of a minute when the sugar solution is permitted to circulate past both sides of the muscle. This sets an upper limit for the time necessary for inorganic cations and organic narcotics to reach the cell surfaces. The action of inorganic cations and organic narcotics upon muscle is slow compared to the time necessary for them to reach the scene of action.

The penetration of the sugar solutions into the intercellular spaces of muscle was found to follow the well known diffusion law, the amount diffusing in being proportional to the square root of the time.

Average values of 77.7 per cent for ρ, the volume concentration of fibers; 231 ohms specific resistance for r2, the resistance of the interior of the fibers; and 71.0° for θ, the phase angle of the impedance locus, were obtained for the muscle in Ringer's solution. How these values change when the muscle is placed in various concentrations of sugar was also studied.

3. The action of a number of organic narcotics upon muscle was studied. All decrease 1000 cycle resistance if the concentration is sufficiently high. A detailed analysis of the action of the narcotic, iso-amyl carbamate, was made, and it was noted that low concentrations increase resistance while higher concentrations decrease it.

By investigating the effect of narcotics upon muscle impedance over a wide frequency range, it was found that during narcosis the resistance of the fiber membranes first increases and then decreases, and, if the drug is present in sufficiently great concentration, membrane resistance may completely disappear. Membrane capacity is only very slightly affected.
BIOELECTRIC POTENTIALS IN VALONIA
Authors: Damon E. B.
Published: May 2004

In their influence on the P.D. across the protoplasm of Valonia macrophysa, Kütz., Li+ and Cs+ resemble Na+, while Rb+ and NH4+ resemble K+. The apparent mobilities of the ions in the external surface layer of Valonia protoplasm increase in the order: Cs+, Na+, Li+ < Cl- < Rb+ < K+ < NH4+.
FACTORS LIMITING BACTERIAL GROWTH
Authors: Hershey A. D.
Published: May 2004

Simple assumptions have led to equations by which the latent period in multiplication and the bacterial numbers expected at any time during the phase of rapid growth may be predicted.

Experimental data obtained under rather diverse conditions have given satisfactory agreement with calculated values. Since the mathematical expressions contain no arbitrary constants, more than accidental significance must be attached to this agreement.

The hypotheses set forth appear completely to describe the early development of Bacterium coli and Bacterium dysenteriae in broth, without postulating differences other than size among individual cells, or cells obtained under different conditions.
REGENERATION OF VISUAL PURPLE IN SOLUTION
Authors: Chase Aurin M. , Smith Emil L.
Published: May 2004

1. Measurements of visual purple regeneration in solution have been made by a procedure which minimized distortion of the results by other color changes so that density changes caused by the regenerating substance alone are obtained.

2. Bleaching a visual purple solution with blue and violet light causes a greater subsequent regeneration than does an equivalent bleaching with light which lacks blue and violet. This is due to a photosensitive substance which has a gradually increasing effective absorption toward the shorter wavelengths. It is uncertain whether this substance is a product of visual purple bleaching or is present in the solution before illumination.

3. The regeneration of visual purple measured at 560 mµ is maximal at about pH 6.7 and decreases markedly at more acid and more alkaline pH's.

4. The absorption spectrum of the regenerating material shows only a concentration change during the course of regeneration, but has a higher absorption at the shorter wavelengths than has visual purple before illumination.

5. Visual purple extractions made at various temperatures show no significant difference in per cent of regeneration.

6. The kinetics of regeneration is usually that of a first order process. Successive regenerations in the same solution have the same velocity constant but form smaller total amounts of regenerated substance.

7. In vivo, the frog retina shows no additional oxygen consumption while visual purple is regenerating.
INCREASE IN BACTERIOPHAGE AND GELATINASE CONCENTRATION IN CULTURES OF BACILLUS MEGATHERIUM
Authors: Northrop John H.
Published: May 2004

1. The increase in bacteria, phage concentration, and gelatinase concentration in cultures of B. megatherium has been determined.

2. With lysogenic cultures the phage concentration, gelatinase concentration, and bacteria concentration increase logarithmically at first. The phage and gelatinase concentration then decrease while the bacteria concentration increases to a maximum.

3. The results are the same with sensitive cultures if the ratio of phage to bacteria is small. If the ratio of phage to bacteria is large phage, gelatinase, and bacteria concentration all increase at first and then decrease. The maximum rate of increase coincides approximately with the maximum rate of oxygen consumption of the culture.

4. 60–90 per cent of the phage is free from the cells.

5. The amount of phage produced is determined by the combined phage and not by the total phage.

6. Phage is produced during growth of the cells and not during lysis.

7. In a very narrow range of pH near 5.55 no increase in bacteria occurs but large increases in phage may be obtained.
CHEMICAL PACEMAKERS
Authors: Hadidian Zareh , Hoagland Hudson
Published: May 2004

1. Iron spicules found in the brains of general paretic patients are formed from endogenous brain iron normally present in another form. This supports our earlier view that the µ value of 16,000 obtained in advanced paretics for alpha brain wave frequencies as a measure of cortical respiration comes about from the slowing of an iron catalyzed link in cortical respiration such as would result from the reduction of available cytochrome and its oxidase, thus making this step a chemical pacemaker.

2. To test the basic theory of chemical pacemakers, a study was made of the succinate-fumarate enzyme system containing succino-dehydrogenase and cytochrome-cytochrome oxidase acting sequentially.

3. The µ value for the unpoisoned system is 11,200 ± 200 calories.

4. According to theory, the addition of a critical amount of cyanide known to be a specific poison of the cytochrome-cytochrome oxidase system (and not of the dehydrogenase) should shift the µ cleanly to 16,000 calories, and it does.

5. According to theory, selenite, a specific poison for the dehydrogenase, should stop all respiration without shifting the µ. This also is found to be the case.

6. The theory also predicts that if the µ is shifted from 11,000 ± to 16,000 ± by cyanide, the subsequent addition of a critical amount of selenite should shift the µ back again to 11,000 ± calories, and this is found to occur.

7. It is concluded that approximately 11,000 calories is the energy of activation of the succino-dehydrogenase-catalyzed step and 16,000 calories is that for the cytochrome-cytochrome oxidase-catalyzed step. These two values are encountered more frequently than any others in physiological systems. It is to be recalled that a shift of µ for alpha brain wave frequencies from 11,000 to 16,000 calories occurs in the course of advancing syphilitic brain infection and is accompanied by a change in form of brain iron.
CALCULATIONS OF BIOELECTRIC POTENTIALS
Authors: Osterhout W. J. V.
Published: May 2004

Values have been calculated for apparent mobilities and partition coefficients in the outer non-aqueous layer of the protoplasm of Nitella. Among the alkali metals (with the exception of cesium) the order of mobilities resembles that in water and the partition coefficients (except for cesium) follow the rule of Shedlovsky and Uhlig, according to which the partition coefficient increases with the ionic radius.

Taking the mobility of the chloride ion as unity, we obtain the following: lithium 2.04, sodium 2.33, potassium 8.76, rubidium 8.76, cesium 1.72, ammonium 4.05, ½ magnesium 20.7, and ½ calcium 7.52.

After exposure to guaiacol these values become: lithium 5.83, sodium 7.30, potassium 8.76, rubidium 8,76, cesium 3.38, ammonium 4.91, ½ magnesium 20.7, and ½ calcium 14.46.

The partition coefficients of the chlorides are as follows, when that of potassium chloride is taken as unity: lithium 0.0133, sodium 0.0263, rubidium 1.0, cesium 0.0152, ammonium 0.0182, magnesium 0.0017, and calcium 0.02.

These are raised by guaiacol to the following: lithium 0.149, sodium 0.426, rubidium 1.0, cesium 0.82, ammonium 0.935, magnesium 0.0263, and calcium 0.323 (that of potassium is not changed).

The effect of guaiacol on the mobilities of the sodium and potassium ions resembles that seen in Halicystis but differs from that found in Valonia where guaiacol increases the mobility of the sodium ion but decreases that of the potassium ion.
PERFORMANCE OF THE HEPP MICRO-OSMOMETER
Authors: Peters Erich , Saslow George
Published: May 2004

Estimation of the molecular weight of horse serum albumin from the osmotic pressure of solutions containing 0.713 to 5.12 gm. per 100 cc. shows that the Hepp osmometer yields the same values as the standard simple osmometer of Adair.

Accuracy and precision of the instrument decrease noticeably at concentrations of albumin less than 0.7 gm. per 100 cc.

A determination in duplicate can be carried out with this instrument in less than 2 hours.

The instrument is easily operated.
STUDIES CONCERNING THE NATURE OF THE SECRETORY ACTIVITY OF THE ISOLATED RINGER-PERFUSED FROG LIVER
Authors: Hober Rudolf , Moore Elinor
Published: May 2004

The ability of the isolated Ringer-perfused frog liver, to concentrate dyestuffs in its secretion several hundred times, can be abolished entirely and reversibly by replacing in the Ringer solution about 1/8 of the NaCl by the isosmotic amount of a surface-inactive non-electrolyte (disaccharide, hexose, pentose, polyhydric alcohol, amino acid, acid amide) or electrolyte (salts of lower fatty acids, hydroxyl carboxylic, and dicarboxylic acids). This effect is not dependent upon changes in the perfusion rate.

The opposite effect, promotion of secretory activity, can be brought about by polar-non-polar electrolytes (salts of higher fatty acids, bile acids, and other aromatic carboxylic acids, aromatic sulfonic acids) and surface-active non-electrolytes (anesthetics, alkaloids, digitonin). However, reversibility of this effect cannot be regularly observed, since cytolysis is frequently the end result.

Suitable concentrations of inhibitory and promoting substances, simultaneously applied, counteract each other.

Inhibitory and promoting substances, in general, exhibit opposite effects upon the dispersion of colloids (starch, lecithin, gelatin).

The correlation between the physicochemical and the physiological action of the organic compounds is discussed.
ON THE PERMEABILITY OF THE STOMACH MUCOSA FOR ACIDS AND SOME OTHER SUBSTANCES
Authors: Teorell Torsten
Published: May 2004

1. Solutions approximately isotonic with blood of strong and weak acids, several salts, glucose, and glycine were introduced in the resting stomachs of cats. The concentration and volume changes were recorded.

2. It was found that the stomach mucosa was permeable to the majority of the ions tested. There was also a permeability in the opposite direction from the blood (mucosa) to the stomach content, particularly of alkali chlorides. Poorly permeable substances were glucose, glycine, and sodium iodate. Pure weak acids such as acetic acid penetrated very rapidly.

3. The electrolyte concentration changes in the stomach content (or gastric juice) are pictured as an exchange diffusion; for instance, the hydrogen ions of an acid are exchanged against alkali ions of the mucosa or blood.

4. It is pointed out that the concept of the mucosa as an ion permeable membrane could be used as the foundation of a "diffusion theory," which can explain the acidity and chloride variations of the gastric juice without postulating neutralizing or diluting secretions.
A DIFFERENTIAL VOLUMETER FOR MICRO-RESPIRATION MEASUREMENTS
Authors: Thimann Kenneth V. , Commoner Barry
Published: May 2004

A modified micro-respirometer employing the differential volumeter principle, and mechanical accessories for the same, are described.

The apparatus enables addition of solutions to be made to the biological material during the experiment. It is of a high sensitivity, a drop movement of 1.0 mm. indicating a volume change of about 0.06 c.mm. It may be used with very small amounts of biological material, provides for convenience in manipulation) and allows readings to be made at 1 minute intervals.

Typical results on plant tissue and protozoa are given.
ELECTRON BOMBARDMENT OF BIOLOGICAL MATERIALS
Authors: Whelden Roy M. , Buchwald Charles E. , Cooper Franklin S. , Haskins Caryl P.
Published: May 2004

A study has been undertaken of the rate of inactivation of spores of the ascomycete fungus Aspergillus niger when bombarded in vacuum, with homogeneous beams of cathode rays of energies from 4 to 15 electron kv. and current densities of 1 x 10–7 to 3 x 10–6 amperes per square cm. These velocities and densities are in the range of those of showers of secondary electrons produced in biological materials irradiated with moderately soft x-rays, and so may be made to serve as quantitative indicators of the mechanics of x-ray action. Four qualitative effects are described.
ELECTROPHORESIS OF PEPSIN
Authors: Herriott Roger M. , Desreux Victor , Northrop John H.
Published: May 2004

1. A number of pepsin solutions containing several protein components have been studied by the electrophoresis method. All samples show a homogeneous boundary moving to the anode at pH 4.4.

2. The activity of this material may be higher than that of the original solution on the basis of total nitrogen but is the same as that of the original solution on the basis of protein nitrogen.

3. There is no separation of the various protein components under these conditions.

4. The apparent isoelectric point at pH 2.7, previously obtained by the collodion particle method is due to the presence of decomposition products. Pure crystalline pepsin, free from decomposition products, is always negatively charged.