Green Background Research Articles

The separation of cone mechanisms in dark adaptation

1. In dark adaptation the threshold is raised as though the bleaching of visual pigment generated an equivalent background. Now Stiles has shown that real coloured backgrounds act selectively upon the various colour mechanisms, so we ask: ;Do equivalent backgrounds from coloured bleachings also act selectively?'2. When dark adaptation was plotted using a blue test flash (Fig. 1b) following bleaching by orange light a kinked curve was obtained. The upper branch was shown to have the same dark adapted threshold as Stiles blue (pi(1)) mechanism and the lower branch as his green (pi(4)) mechanism. The pi(4) dark adaptation curve alone (unkinked) was obtained using a white instead of an orange bleach.3. Dark adaptation curves were obtained in which the test flash was presented upon various steady backgrounds. In conditions where only pi(4) was involved (Fig. 3) the experimental results fitted the curves calculated on the assumption that the equivalent background of bleaching simply adds to the real background in raising the threshold-a condition already established for rods.4. In conditions where pi(4) and pi(1) were both present (blue test, yellow-green background and white bleach) kinked dark adaptation curves were obtained (Fig. 2) where the upper branch (pi(4)) coincided with those of Fig. 3 and the lower were due to pi(1).5. The blue mechanism recovers in dark adaptation at about the same rate as red and green, or slightly slower.6. Dark adaptation curves with red (pi(5)) and green (pi(4)) limbs can be obtained after a deep red bleach (Fig. 4) using a red test flash and a green background. The red and the green limbs were also plotted alone in their entirety by slightly changing the conditions.7. We are led to the idea of three colour mechanisms that adapt as independently one of another after bleaching as they do with backgrounds.8. Though this simple independence accounts for the wide and conspicuous range of adaptive phenomena, we have encountered some special conditions (not here described) that seem to imply a measure of interaction between the different colour mechanisms.

TWO DIFFERENT MANIFESTATIONS OF ENHANCEMENT IN THE PHOTOSYNTHESIS OF PORPHYRIDIUM CRUENTUM IN FLASHING MONOCHROMATIC LIGHT*

Abstract— Oxygen evolution from Porphyridium cruentum exposed to monochromatic light flashes with background light of different wavelengths and intensities was measured. Two different manifestations of the enhancement effect were found: (1) Type I (also referred as EH): an increase in the rate of O2 evolution and (2) Type II (also referred as Et): a prolongation of O2 evolution in time. Exposure of algae to red flashes with green background light revealed both types of enhancement whereas green flashes with red background light revealed only the first type of enhancement. Similar results were observed under both aerobic and anaerobic conditions except that in the latter, complications arise due to S‐shape of the curve of rate of photosynthesis versus light intensitity in a nitrogen atmosphere.The results presented in this paper and those presented in the earlier papers of French have been interpreted in terms of the ‘spill‐over’ and the ‘separate package’ model for the distribution of light energy into the two pigment systems. In both the models, we incorporate the idea that the product of light reaction I is long‐lived (half‐life of the order of seconds). No assumption is needed about the life time of the photoproduct of reaction II in the spillover model; in the separate package model, however, we have to incorporate an additional assumption that photoproduct II is short‐lived (half‐life less than 4 msec) to explain all the results.

Errorless transfer of a discrimination across two continua.

A procedure developed earlier (Terrace, 1963) successfully trained a red-green discrimination without the occurrence of any errors in 12 out of 12 cases. Errorless transfer from the red-green discrimination to a discrimination between a vertical and a horizontal line was accomplished by first superimposing the vertical and the horizontal lines on the red and green backgrounds, respectively, and then fading out the red and the green backgrounds. Superimposition of the two sets of stimuli without fading, or an abrupt transfer from the first to the second set of stimuli, resulted in the occurrence of errors during transfer. Superimposition, however, did result in some "incidental learning". Performance following acquisition of the vertical-horizontal discrimination with errors differed from performance following acquisition without errors. If the vertical-horizontal discrimination was learned with errors, the latency of the response to S+ was permanently shortened and errors occurred during subsequent testing on the red-green discrimination even though the red-green discrimination was originally acquired without errors. If the vertical-horizontal discrimination was learned without errors, the latency of the response to S+ was unaffected and no errors occurred during subsequent testing on the red-green discrimination.

Staining mitochondria in fixed blood smears.

Wet blood smears are placed immediately in Helly's fluid for 24 hr, transferred directly to a saturated solution of potassium dichromate for 48 hr and washed in running water for 2-4 hr. The slides are then treated with iodine and sodium thiosulf ate and washed several hours or overnight. Excess water is removed by blotting the slide around the smear, Altmann's aniline fuchsin is placed on the smear and the slide is heated over a spirit lamp until white fumes appear. After the slide cools the stain is poured off and the excess removed by washing with distilled water. Methyl green (1% aqueous) is dropped on the smear and left for approximately 30 sec. It is then passed rapidly through 2 changes of absolute ethanol and into xylene, from which it is mounted in Permount. This stains mitochondria, red blood corpuscles and specific granules of eosinophilic granulocytes red on a green background.

Peripheral contrast thresholds for various and different wavelengths for adapting field and test stimulus.

Measurements of the contrast threshold for peripheral vision for size d of the circular test spot between 4′ and 420′ and for flash time t between 0.02 and 1 sec are presented. Wavelengths for adapting field λ1 and test stimulus λ2 6500 and 5250A so that four λ1 − λ2 combinations were explored. The merits of theoretical speculations on the perception of contrast considering the statistical fluctuations in the number of incident quanta and nerve impulses are discussed.It proved that the perception of red light is dominant over the stimulation of the rod system by the background and that the state of adaptation of the one eye and the perception of light via this eye is not affected or influenced by the actual stimulation or state of adaptation of the opposite eye when influences due to variations in pupil size are eliminated. Exception must be made for very high brightnesses of a green background.

Book Reviews

MESSRS. E. F. RICKETTS and J. Calvin have revised their well-known book on the littoral fauna of the west coast of America. Written by laymen collectors for the layman, it stimulates his curiosity about the prolific life of the sea-shore and deals with the Subject from the ecological rather than the taknomic point of view. Animal communities of the protected outer coast, open coast, bays and estuaries, and wharf piles are described, each area being again subdivided according to the substratum. These chapters are illustrated by photographs from living animals, making forty-fix plates, and 129 line-drawings. A few of the plates (for example, 39, 43) have lost somewhat in brightness ; but the magnificent colour-plate of Pacific chitons, on its green background, which forms the frontispiece, is a most attractive and useful addition. The littoral section has cross-references from text to plate and vice versa. The original text remains unaltered, except for the correction of minor errors.

Eye-Movements in Reading Black Print on White Background and Red Print on Dark Green Background

Eye-Movements in Reading Black Print on White Background and Red Print on Dark Green Background

On the responses of the african migratory locust to different types of background

It is known that the hoppers (or immature forms) of certain species of locusts, in the solitary phase, bear a marked colour resemblance to the immediate environment in which they are living. They are, for example, green when living among fresh green vegetation, light brown on sand, speckled greyish white on white limestone rocks, and so on. Faure (1932) conducted a series of experiments with Locustana pardalina (Walk.) and Locusta migratoria subspecies migratorioides R. and F. in South Africa. His object was to discover whether there was only a coincidence between the prevailing coloration of the hoppers of these two species and that of their environment, or whether a genuine colour adaptation is involved. He isolated a number of young hoppers, of the same stock, placing each insect in a separate wooden box, provided with a sliding glass lid and reared it to the adult instar. The wood of each box was painted on the inside with ordinary commercial oil paints and, when dry, the latter were compared with the coloured plates of Ridgway (1912) and named according to the tints which they resembled most closely. The experiments of Faure were done out of doors, and he recorded the general coloration assumed by each locust during and at the end of the experiments, noting them as “good”, “fair”, “slight” or “none”, according to the degree of resemblance their coloration bore to that of the insides of the boxes. He obtained a majority of “good” or “fair” resemblances on white, black, grey, yellow and brown backgrounds in the boxes, and one striking resemblance on a black and white striped background. No resemblance occurred when confined in boxes painted green, pink, blue, or with black and orange stripes. Faure also carried out some other experiments on a smaller scale, such as using glass lids of the colours resembling those of the walls of the boxes, but these, as he states, were, on the whole, inconclusive. He brought forward evidence, however, of great importance as regards the production of green hoppers. These, he found, did not result in response to a green background and were only produced in the presence of a moist atmosphere and an abundance of succulent food. He further showed that the green colour-producing substance was spectroscopically very different from chlorophyll, and prepared extracts showed none of the characteristic fluorescence. The present paper describes experiments which have been made with a view to determining the relation between the general coloration of the hoppers and the wave-lengths of the effective colours forming different backgrounds.

The Bronzes of Luristan

SO little is known about the bronzes of Luristan, and their interest to the archaeologist and historian is so great, that any one who has had the good fortune to enter at all into that little-known country is justified in recounting his experiences. I was able to travel last October from Nihavand over the Varazan pass to Khava, thence to Alishtar, back again through Khava into Dilfan, and from Dilfan by Chavari through Duliskan to Tudaru, which seems to be at present the southern limit for the police of the district; thence I went south half a day's ride along the Gizarud and up a little valley, hitherto unnamed on the maps, which I discovered to be that of the Kangaveri river, leading to Sari Kashti, the northern centre for the Luristan bronzes, in a landscape full of ancient looted cemeteries. I had no opportunity to see more than one grave actually being opened, and I am no expert to develop theories about them, but it may be useful to put down all I could notice or discover, and leave it to minds better equipped to draw conclusions. I have written elsewhere the account of the actual travelling and its adventures, and will confine myself to what concerns the graves and their possible history. Special interest has been centred on those graves which are said to contain the trappings of horses and chariots, for the origins of the people who used such things may throw light on the coming of the horse into Persia. When the bronzes first appeared on the market, carried by tribesmen over the Luristan passes to Kermanshah or to Harsin, it was thought that the plains of Alishtar and Khava would be the home of this horse-breeding nation; for these plains were supposed, after Sir H. Rawlinson marched across and saw them in 1836, to be the Nisaian pasture lands of the Achaemenian kings. But though the two plains are sprinkled with old mounds and cemeteries, I could find nothing there belonging to a horse, nor had any grave with a horse's skeleton inside it been found there. There is a mound by a village called Qal'a Kafrash in Khava where I found a shard of early Islamic painted ware, a carved arabesque on pale green background. There is another mound at Beira, also in Khava, where a bronze dagger had been found. In the south of Khava there are graveyards round the great mound of Cheha Husein, and the people told me that bronzes had been found there; nothing however of the more elaborate kind of Luristan work with carved masks and animals, and nothing in the way of harness. In Alishtar it was the same. The site of the ancient city of Alishtar is full of gravestones of a peculiar kind, about 5 feet by 2 feet, with a scroll of ornament or Arabic script running round them, and a carved knob at each corner; near them on the ground one may pick up fragments of Islamic glazed ware; and one comes upon these tombstones elsewhere in Alishtar, at the old village of Deh Ram for instance. There is the tradition that, on the site of the ruined city, an old minaret still existed a few years ago when the Government troops, who were destroying the power of Mir Ali Khan, razed it to the ground as a possible stronghold for rebels: from the descriptions I was able to obtain this minaret must have been something like that of Saveh, a plain tubular shape covered with ornamented brickwork: the bricks are still lying about; the site seems to

Differential Stain for acid fast Bacteria and Spores

A modified method of staining acid-fast organisms is described. After staining with carbol-fuchsin as usual in the Ziehl-Neelson method, wash with water and while the slide is still wet cover with a saturated acetone solution of malachite green for three to five minutes. Wash and examine. The acid-fast organisms and spores are red in a green background. If the smear is thick and appears too dense, dry for three minutes and hold over the mouth of a bottle of ammonia until decolorized to suit. Upon exposure to the air the green returns. This can be prevented by keeping the smear alkaline, by the addition of sodium bicarbonate.A second method is described for use with sputum in which acid-fast organisms are scarce. It permits the examination of thick smears and therefore increases the chances of finding tubercle organisms when few in number. Stain with carbol fuchsin as in the Ziehl-Neelson method. Decolorize with 30% phenol-disulfonic acid in water for a few seconds or until decolorized. Wash and examine at...

VASODILATATION IN FUNDULUS DUE TO A COLOR STIMULUS

Previous articleNext article FreeJournal ArticlesVASODILATATION IN FUNDULUS DUE TO A COLOR STIMULUSC. J. CONNOLLYC. J. CONNOLLY Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Biological Bulletin Volume 50, Number 3March 1926 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.2307/1536670 Views: 2Total views on this site © 1926 Marine Biological LaboratoryPDF download Crossref reports no articles citing this article.

ADAPTIVE CHANGES IN SHADES AND COLOR OF FUNDULUS

1. Adaptive changes in shade occur in Fundulus heteroclitus when placed on white, gray, and black backgrounds. This adaptation is brought about by the contraction or expansion of the melanophores.2. On colored backgrounds for short periods, adaptation in only shade occurs.3. Prolonged stimulation by colored backgrounds brings about adaptation in color. This occurred in yellow, red, green, and blue environments.4. The experiments with spectral lights of different wave-lengths but of the same radiant energy or intensity, show that the melanophores respond similarly at all wave-lengths, the contraction being due to light intensity.5. The response to the longer wave-lengths, red and especially yellow, in causing an expansion of the xanthophores, though intensity was the same as in the blue on short wave-length end of the spectrum, shows that the quality of light or wave-length has a specific influence on the coloration of Fundulus.6. The stimuli causing changes in shade and color are received through the eyes.7. The changes in color are brought about by the degree of expansion or contraction of the melanophores and xanthophores combined with the optical properties of the guanophores or iridocytes and the reflecting layer. The guanophores are frequently found associated with the melanophores.8. Adaptive change to a yellow background is brought about by a maximum expansion of xanthophores and a maximum contraction of the melanophores.9. In fishes adapted to a red background, the xanthophores are only partially expanded and the melanophores contracted. The pink color is due chiefly to a dilation of the blood capillaries.10. In fishes adapted to a green background, the green tints present in the normal light adapted fish, is increased and is especially noticeable above the eyes. The xanthophores and melanophores are partially expanded.11. In blue adapted fishes the xanthophores are maximally contracted and the melanophores in the deeper portions of the dermis and upon the proximal parts of the scales, are expanded.Postscript. Since the preparation of this paper I have had the opportunity of repeating the experiments on Fundulus at the St. Andrew's Biological Station. My results have been the same as those obtained in the Harvard Laboratory-except that I failed to get on a red background the pink coloration and vaso-dilation described in this paper. Whether this is a seasonal or a local difference in the fishes remains to be worked out.