SUPPRESSION OF PHOTOTROPIC CIRCUS MOVEMENTS OF LIMAX BY STRYCHNINE

By injection with strychnine the phototropic circus movements of the slug Limax maximus may be suppressed, its phototropism abolished. The creeping activity of the foot is not in any essential way interferred with. Strychnine produces in Limax central nervous effects of the sort associated with its characteristic action. Hence, although an effect of the drug upon photoreceptors cannot be definitely excluded, the experimental result is held to demonstrate that in orientation during circus movements there occurs central "competition" between impulses resulting (1) in the release of pedal waves and (2) in the maintenance of a turning posture.     

PHOTOTROPIC CIRCUS MOVEMENTS OF LIMAX AS AFFECTED BY TEMPERATURE

1. The theory of animal phototropism requires for particular instances a knowledge of the action of light as exerted through each of two bilaterally located receptors functioning singly. The measurement of "circus movements" which this involves must be concerned with such aspects of the reaction as are demonstrably dependent upon the effect of light. 2. The negatively phototropic slug Limax maximus exhibits very definite and continuous circus movement under vertical illumination when one eye-tentacle has been removed. The amplitude of the circling movement, measured in degrees deflection per cm. of path as an index of maintained differential tonus, is intimately related to the concurrent velocity of creeping. Analysis of the orienting mechanism is facilitated by the fact that in gasteropods such as Limax the animal creeps by means of the pedal organ, but orients (turns) by a totally distinct set of muscles in the dorsal and lateral regions of the body wall. 3. The expression of the phototropic orienting tendency, with illumination constant, is greatly influenced by the temperature. Above a zone centering at 15°, the amplitude of turning (degrees per cm. of path) is determined by the temperature in accurate agreement with Arrhenius'' equation for chemical reaction velocity, with the critical increment µ = 16,820; and the rate of creeping is progressively less as the temperature rises, µ for its reciprocal being 10,900. Below 15°, the velocity of creeping becomes less the the lower the temperature, µ being again 16,800; while the amplitude of orientation is limited merely by the velocity of creeping, its reciprocal being directly proportional thereto. 4. Measurements of Limax circus movements in terms of turning deflection as function of light intensity must therefore be carried out at a temperature well above 15°. 5. The analysis provides a gross physical model of how an end-result may be influenced by temperature according to the effect of temperature upon each of several interconnected processes when the "temperature vs. effect" curves for these processes dynamically intersect. 6. It is pointed out that a certain type of unpredictability (quantative variability) in animal behavior under "normal" natural conditions probably results from dynamic equilibrium there obtaining between diverse mechanisms competing for effector control (in the present case, the creeping mechanism and that for turning, in the range 14–16°C.). It follows that the unraveling of the elements of conduct necessitates experimentation under diverse abnormal conditions favoring individual mechanism of response.     

THE PHOTOTROPIC EFFECT OF POLARIZED LIGHT

For the growing cell of Phycomyces, a difference in the phototropic effect of light is described depending on its plane of polarization with reference to the axis of the cell. The difference which is found is primarily due to differences in the reflection losses at the cell surface. The magnitude of the effect approximates that deduced from the theory of phototropism suggested for this system. No specific effect of plane polarized light on the growth processes of the cell need be postulated.     

ON THE EQUILIBRATION OF GEOTROPIC AND PHOTOTROPIC EXCITATIONS IN THE RAT

The intensity of light required to just counterbalance geotropic orientation of young rats, with eyelids unopened, is so related to the angle of inclination (α) of the creeping plane that the ratio log I/log sin α is constant. This relationship, and the statistical variability of I as measured at each value of α, may be deduced from the known phototropic and the geotropic conduct as studied separately, and affords proof that in the compounding of the two kinds of excitation the rat is behaving as a machine.     

THE PHOTOTROPIC MECHANISM IN RANATRA

Definite proof is obtained that in the phototropic orientation of Ranatra the relative postures of the appendages, resulting in a bilateral difference of effective stroke in swimming, is the mechanism of orientation; the frequency of locomotor movements is the same on the two sides of the body.     

THE PHOTOTROPIC SENSITIVITY OF PHYCOMYCES AS RELATED TO WAVE-LENGTH

Under the circumstances of experimentation described, the sporangiophores of Phycomyces are found to be most sensitive to stimulation by light in the violet between 400 and 430 mµ. Toward the red, sensitivity falls to nearly zero near 580 mµ, while in the near ultra-violet around 370 mµ, sensitivity is still high. The previous experiments of Blaauw had placed the point of greatest sensitivity some 80 mµ nearer the red end of the spectrum. Because of the known presence in the sporangiophores of Phycomyces of "accessory" pigments, care must be taken in identifying such results with the absorption spectrum of the photosensitive substance.     

THE MEASUREMENT OF GALVANOTROPIC EXCITATION

The expression of galvanotropic excitation in energy units is obtained by the measurement of the current densities required to balance phototropic excitation (or reciprocally). With the triclad Leptoplana preliminary measurements show that the current is proportional to the logarithm of the light intensity.     

THE LOCOMOTION OF LIMAX : I. TEMPERATURE COEFFICIENT OF PEDAL ACTIVITY.

Pedal progression of the slug Limax maximus was studied to obtain relations between wave velocity on the sole of the foot, wave frequency, the advance due to a single wave, and the velocity of vertically upward creeping. Each of the first three quantities is directly proportional to the simultaneous velocity of progression. Under comparable conditions, that is when work is done at a constant rate, the frequency of pedal waves is influenced by the temperature according to the equation of Arrhenius, with µ = 10,700 (Q ₁₀ for 11° to 21° = 2.1). The velocity of a single wave must have very nearly the same "temperature characteristic," which is found also in another case of nerve net transmission (in Renilla).     

GROWTH AND REPRODUCTION OF THE SLUG LIMAX VALENTIANUS FIRUSSAC IN EXPERIMENTAL CONDITIONS

Growth and reproduction of batches and isolated Limax valentianus Férussacslugs reared under long-day photoperiods were compared with thosereared under short-day photoperiods combined with higher temperaturesduring the dark period. Weight increase in L. valentianus occurredin three distinct phases: an initial phase of rapid growth (infantilephase), followed by a phase with a smaller increase in weight(juvenile phase) and finally a phase with minimal growth, duringwhich reproduction occurred (adult phase). This phase ended witha weight decrease, due to senescence. Short days associatedwith an increase in temperature during the night reduced thereproductive rate, but did not affect growth. Long days werefavourable for reproduction. Growth rate was fastest in isolatedindividuals reared under long days and warm nights, while reproductionwas greatest in isolated individuals reared under long daysand cool nights. Fertility generally decreased with age, butegg production of slug batches evolved through a maximum, occurringbefore mean life span. High slug density reduced reproductiverate and longevity. (Received 22 December 2000; accepted 10 October 2000)     

THE LOCOMOTION OF LIMAX : II. VERTICAL ASCENSION WITH ADDED LOADS.

In Limax the lifting of additional loads during vertical ascension does not alter the law of linear proportionality between speed and frequency of pedal waves, or that between speed and dimensions of the single waves; for equal velocities of progression these quantities are the same, regardless of the mass lifted. The pedal organ of the slug, although under the control of central impulses, is thus essentially an independent effector.     

FIELD STUDIES OF HOMING IN THE PULMONATE SLUG LIMAX PSEUDOFLAVUS (EVANS)

Excursions of Limax pseudoflavus (Evans) were recorded over9 days using time lapse cinematography. Excursions were madeat night, ending before sunrise, and were significantly morefrequent in wet than in dry weather. The homes of these slugsare species rather than population or individual specific. Animalstended to home upwind but the direction in which they left homewas not significantly correlated with wind direction. Trailfollowing may be involved in homing. All but one example ofhoming may be interpreted in terms of distant chemoreception,rheotaxis and trail following. Using these mechanisms alonea slug's best strategy for feeding and homing is discussed. (Received 15 March 1979;     

TEMPORARY ABOLITION OF PHOTOTROPISM IN LIMAX AFTER FEEDING

When fed upon cooked potato the slug Limax maximus becomes for a day or more indifferent to light—its natural negative phototropism is suppressed. This effect is not produced by raw potato or other diets; it can be duplicated by injection of sugar solutions into the stomach or into the body fluids, and seems to be due to sugar absorbed during the digestion of the cooked starch. The fact is of interest particularly for the suggestion which it affords as to the explanation of fluctuations in conduct.     

THE QUANTIC AND STATISTICAL BASES OF VISUAL EXCITATION

In the article entitled "The quantic and statistical bases of visual excitation" (J. Gen. Physiol., 1947–48, 31, 269), in footnote 1, at the bottom of page 274, read, The product k (k–1) ..., may be written See PDF for Equation. On page 284, in equation (1) add, t = mτ; m = 1,2,3.... I take this occasion to call attention to the fact that in 1944 van der Velden developed two equations, one of which described the variation of liminal energy with the flash time and the other this variation with the visual angle of the spot; both of them apply in the case of homogeneous populations of receptors (rods). These equations are very similar to mine, obtained in an entirely different manner and published nearly 4 years later. In fact, until very recently I was not aware of the equations of van der Velden, published in Physica, 1944, 11, 179, because the papers published in that journal, and particularly those which are written in Dutch, generally become known to French physiologists as abstracts which are often incomplete. Thus the priority of the theoretical basis of the empirical laws which are directly related to the two equations in question belongs entirely to van der Velden. ERNEST L. M. BAUMGARDT In Vol. 31, No. 3, January 20, 1948, page 261, in equation (1) for H ₂ read H ₁. On page 262, in equation (5) for H read H ₂. On page 265, in the third line from the bottom of the page, for 4 c.mm. read 5.24 c.mm. On the same page, in the second line from the bottom of the page, for 5 c.mm. read 6.86 c.mm.     

ON THE EXCITATION OF TISSUE BY MEANS OF CONDENSER DISCHARGES

Equations are derived for the capacity-voltage relations for stimulation of tissue by condenser discharges, using the hypothesis that the local excitatory process p grows under the influence of an applied potential V according to the equation, See PDF for Equation where K and k are constants. It is further assumed that the local excitatory process becomes adequate when it attains a value h ± α V where h and α are constants and V is the applied potential at the particular instant that the adequate value is attained. The equations so obtained are applied to the data of several authors on several types of tissue and the agreements obtained are sufficiently good. It is shown in one case that the direct current equation and the condenser discharge equation each derived from the above bases are consistent when applied to data from the same preparation.     

盘基网柄菌理论模型中的硬激发

本文对J.L.Martiel＆A.Goldbeter提出的共价酶修饰模型作了数值计算.发现了一些新现象,如共振和硬激发现象,并很好地用来说明盘基网柄菌在间期期间控制分化和趋化的cAMP的振荡和传播过程.     

迷走神经兴奋对HRV的影响及其机制的初步分析

实验在氯醛糖加氨基甲酸乙酯麻醉的新西兰兔上进行。记录血压、心率、心电图和心率变异性（ＨＲＶ）频谱分析。电刺激减压神经（ＤＮ）,疑核（ＮＡ）和右侧迷走神经（ＲＶ）外周端,均引起心率和血压下降（Ｐ＜０．００１）,总变异性（ＴＶ）、低频成分（ＬＦ）、高频成分（ＨＦ）、ＬＦ／ＨＦ比值（ＬＦ／ＨＦ）和极低频成分（ＶＬＦ）增大（Ｐ＜０．０５－０．００１）。静脉注射阿托品可使上述反应显著减小（Ｐ＜０．０５－０．０１）,而静脉注射心得安仅可阻断ＤＮ和ＮＡ所致ＬＦ的增大（Ｐ＜０．０５）。以上结果表明：迷走神经是ＨＲＶ的主要调节者之一;ＨＦ由迷走神经单独介导;ＬＦ受迷走神经和交感神经共同调制;迷走神经参与ＶＬＦ波的形成