bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE PHYSIOLOGICAL EFFECTS OF PRESSURE
Authors: CATTELL McKEEN 
Published: January 2008

SummaryOur knowledge of physiological effects of pressure is as yet too incomplete to permit of generalizations, and we are still very much in the dark regarding the mechanism of pressure action. Any influence of hydrostatic pressure must be secondary to a decrease in volume. In non‐living systems this results in important changes in physical and chemical properties and gives a basis for the explanation of the changes produced in living material. Such factors as the velocity of chemical reaction and the viscosity of fluids are, in general, increased quite out of proportion to the volume change. High pressures bring about an irreversible polymerization of many substances, including proteins. The same order of pressure inactivates most enzyme solutions, bacterial toxins, antibodies, viruses, and other biological agents. The simpler forms of life, such as bacteria and yeast cells, are only slightly less resistant, but all are killed by sufficiently high pressure. On higher forms relatively low pressures cause death, especially when long continued.There are many known instances where small pressures cause a stimulation of physiological processes, and this may prove to be a general phenomenon occurring at pressures below those resulting in depression. In the case of muscle contracting under pressure there is a marked augmentation in the response, and the application of pressure may, independently of any other form of stimulus, result in the prolonged liberation of energy. Provided that the pressure increase is not too extreme, all the changes observed are reversed with decompression.The action of pressure on physiological mechanisms has a special interest because it is a fundamental one on molecular relationships extending throughout the cell structure. Furthermore, it is an agent which can be supplied and removed with great rapidity and as such provides a unique tool for the study of physiological problems.
ÜBER DIE TIERGEOGRAPHISCHEN VERHÄLTNISSE DER CIRCUMANTARKTISCHEN SÜSSWASSERFAUNA
Authors: BREHM V. 
Published: January 2008

SummaryThis review gives a survey of endemic organisms of the fresh‐water fauna of the circumpolar regions, which have geologically, but not ecologically, separate habitats. A number of examples has been selected which indicate that various animals occur in approximately the same geographical distribution areas as Irmscher established for his plants, although the insufficiency of our knowledge of large regions (e.g. Western and Northern Australia, New Guinea, the west of the Argentine Republic) does not allow of the zoological maps being so complete as the botanical. The similarity of the animal and plant results, however, may perhaps support Wegener's theory.
INSECT SURVIVAL IN RELATION TO THE RATE OF WATER LOSS
Authors: G. JOHNSON C. 
Published: January 2008

Summary1. If the relationship between rate of water loss from an insect and saturation deficiency is linear and survival is limited only by water loss, then the curve of longevity against saturation deficiency is hyperbola‐shaped. The position of this curve with respect to the co‐ordinates is, however, affected by other factors, which are discussed.2. The work of Bacot & Martin (1924) on the longevity of the rat flea, Xenopsylla cheopis, is reviewed in the light of the above hypothesis: errors in curve fitting are revealed which make it necessary to modify some of Bacot & Martin's conclusions.3. Selected data from various authors subsequent to Bacot & Martin are considered. The discrepancies, real and apparent, between Leeson's results with rat fleas and those of Bacot & Martin are analysed, and it is pointed out that these were to some extent due to errors in curve fitting. The hypothetical relationship between longevity, rate of water loss and saturation deficiency set out in the first part of this article are illustrated by Ludwig's (1937) data for Popillia japonica; the linear relationship between 1/longevity and the rate of water loss demonstrates the hypothesis that water loss limits survival with this insect. Other less complete data are also discussed.4. Various types of longevity‐saturation deficiency curves are described and the causes which probably account for such variations.5. The relationship of pupal or egg mortality to saturation deficiency cannot by itself throw light on the variation of rate of water loss with saturation deficiency; the time factor must also be taken into account. Lines of equal mortality may coincide with lines of equal saturation deficiency (the co‐ordinates being relative humidity and temperature), so that the product of mortality and saturation deficiency is constant at any one temperature; but this indicates only that temperature is without effect on mortality and does not throw light on the relation of mortality to different saturation deficiencies. Such coincidence of lines cannot, therefore, be taken as proof that Dalton's law operates.This work was done while I held the Avebury Studentship in the Department of Entomology, London School of Hygiene and Tropical Medicine, and I am greatly indebted to Prof. P. A. Buxton for his great kindness and ready help. I also thank Drs W. J. Martin and D. L. Gunn for their advice and criticism.
ON THE DEVELOPMENT OF FEATHERS
Authors: LILLIE FRANK R. 
Published: January 2008

SummaryI. Feather papillae are regarded as individually persistent throughout life, from the time of their origin between the sixth and ninth days of embryonic life. In each feather tract the order of origin is significantly related to dynamic field properties of the tract, such as growth rates, degrees of asymmetry, etc.2. Recent work on the anatomy and development of the rhachis with special reference to barb relations and the independent origin of the central rhachis is considered; also the development of the after‐feather and of the pulp and its blood supply.3. By plotting axial growth and isochrones on the vane of the feather it is possible to relate any definitive locus to its time and place of origin in the germ, and hence to the conditions of its determination.4. The papillae of definitive feathers may be transplanted, or subdivided, or parts of papillae of different tracts may be recombined. The results of the operations show that papillae have a definitive bilateral organization, like amphibian eggs, for example; that they are tract‐specific; and that a dorsal field, including the central rhachis, exerts a dominant influence on development. Various abnormalities of feather form produced may be interpreted. Twins and chimaerae may be produced. Abnormalities artificially produced persist through successive generations of feathers from the same follicle. The mesoderm of the papilla is regarded as the seat of the initial inductions.5. The melanophores of feather germs are derived from the neural crest. When transplanted to foreign fowl hosts they determine the donor pattern in the host, as, for instance, barring in a white host. The genotypic composition of the donor melanophore is the controlling factor in both colour and pattern of the host feather in these experiments in all breeds of fowl examined.6. The growing feather germ is a very sensitive indicator; reactions may be read by pattern modifications in the finished feather and referred to their locus of origin in the germ (cf. no. 3).7. The thresholds of reaction of feathers to female hormone increase in proportion to rates of axial growth. This is very conspicuous with reference to the discontinuous rates of different tracts, and is also to be observed with reference to gradations of growth rate within a single tract.8. Within the individual feather germ of breast and saddle tract, threshold of reaction to female hormone and thyroxin rises from dorsal to ventral loci of the collar. These transverse gradients produce transverse patterns on the vane of the feather varying in form according to rise and fall of hormone in the blood stream by absorption and excretion after injection: the principle of rate of reaction which is inversely proportional to threshold is also a factor in the determination of pattern.9. The principles of physiology of development may be applied to some problems of physiological genetics, as, for instance, in the case of barred patterns.
THE NUMBER CONCEPTION IN ANIMAL PSYCHOLOGY
Authors: HONIGMANN H. 
Published: January 2008

Summary1. The first attempts to approach the problem of number conception in animals consisted in a training to identify one object out of many by its relative position.2. The multiple‐choice method, although an advance on previous work, has yielded relatively poor results. The only apparent exception, namely the striking results obtained with finches, is probably due to a technical error.3. Experiments with a temporal maze have shown that it is extremely difficult for animals to perform a double alternation, and no animal has yet been trained to perform this more than once successively. Claims that some birds are able to select every third out of a line of similar objects are without convincing foundation owing to the lack of adequate control tests.4. The experiments of Verlaine and his collaborators led to the belief in a genuine number conception in animals, but the lack of satisfactory controls deprives the results of these cleverly devised experiments of validity.5. Bierens de Haan repeated these experiments on a sound basis with the necessary controls. He found that the animals trained themselves to perform two or three single actions in a certain rhythm, and that consequently increasing the intervals between the single actions destroyed the training.6. Systematic investigation of the two basic abilities of performing an action a certain number of times and of discriminating between two quantities of objects gave the interesting result that the limit in both cases is respectively 6 or 5:6 for all animals investigated. The discrimination between 6 and 7 has never been achieved.7. Experiments with parrakeets gave better results than with pigeons, but both groups were surpassed by the achievements of jackdaws. The latter were able to learn four different kinds of number training, and to make use of them simultaneously. They could also to a certain extent combine both basic abilities. But a close analysis of these surprising accomplishments shows that even here any counting or number conception in the human sense of the word does not exist.
NUCLEAR and SOMATIC PHASES IN THE FLORIDEAE
Authors: DREW KATHLEEN M. 
Published: January 2008

Summary(i) The need for a considerable extension of morphological and cytological work in the Florideae is pointed out. (2) Before proceeding to the survey current terminology is reviewed; some terms are discarded and definitions are given for those retained. The survey shows that our cytological knowledge is limited almost entirely to two of the six orders, the Nemalionales and Ceramiales. Members of the Nemalionales show great variety as regards the somatic phase sequence in the life history. Species investigated cytologically, to varying degrees of detail, are all of the Nemalion type, that is, two morphologically dissimilar haploid phases separated by a very short diplophase of the nucleus. The Gelidiales have been completely neglected, and apart from Corallina officinalis var. mediterranea so have the Cryptonemiales. In this latter order there are indications of ‘atypical’ phase sequence. This is also true of the Gigartinales which include in addition forms showing the Phyllophora Brodiaei type of life history, i.e. two morphologically dissimilar phases, one a gametophyte and the other a tetrasporic nemathecium developed from the auxiliary cell. The nuclear phase sequence is unknown. Information about the nuclear history in the Rhodymeniales is only sufficient to indicate problems in need of investigation. In the Ceramiales the Polysiphonia type of life history with three somatic phases (two morphologically similar) and two nuclear phases appears to be general, and detailed accounts of such exist for several species. Other types are known and representatives have been investigated: Spermothamnion Turneri has been shown to be cytologically polyphasic and to be characterized by the formation of functional sexual organs on the diploid; the polysporangium of S. Snyderae has been shown to be a compound tetrasporangium, and Plumaria elegans has been found to have three nuclear phases, the triploid bearing a special type of sporangium. In addition, some species show unusual somatic phases sequences, the nuclear phases being unknown. (3) Three lines of cytological research are envisaged associated with ecological and physiological investigations. (4) There is a striking absence of physiological concepts concerning the Florideae and hence the need for pure culture and general physiological investigations.I wish to express my thanks to Prof. C. W. Wardlaw for his stimulating interest and help in the preparation of this article, and also to the Council of the University of Manchester for library facilities. Thanks are also due to Mr E. Ashby for his help in the production of the figures. Owing to war‐time restrictions direct copying of previously published figures has not been possible. Instead they have been photographed and magnified considerably in order that the photographic image could be meticulously picked out in Indian ink. Subsequently the diagram was cleared by bleaching and reduced to its original size. I trust that faithful copies of the originals, as published, have thus been obtained.
THEORETICAL ASPECTS OF BACTERIAL CHEMOTHERAPY
Authors: MCILWAIN HENRY 
Published: January 2008

SummaryHigher organisms and micro‐organisms exhibit many types of mutual action and association, and that type of interaction in which the micro‐organism becomes a parasite is normally prevented by the potential host. If parasitism is established its course may be impeded by administration of substances to the host; interaction in the resulting system of drug, parasite and host then constitutes chemotherapy.The interactions of successful bacterial chemothera‐peuticals with the parasites, apart from the host, show characters which in most cases afford a basis for their effects in vivo. Their action may be to retard bacterial growth, as is the case with sulphonamides. They may stop the use by the parasite of substances which protect it from the host, as do the antipneumococcal polysaccharidases; or they may react with bacterial products which are injurious to the host, as do antitoxins. Such actions are susceptible to further analysis. The effects upon growth have been found to be associated with particular substances whose nature in several cases has suggested the mode of action of the inhibitor. Hypotheses based upon such findings have enabled certain new types of agents to be prepared, and reasons given for their structural specificity. Processes of the parasite, which are affected by chemotherapeuticals, have also been characterized by following the influence of the agents upon the course of growth of the parasite. A beginning has been made to specifying such influence in terms of effects upon isolated metabolic processes and other events in the parasite.Interaction of the host with both parasite and antibacterial agent or potential agent condition the issue in chemotherapy. The concentrations of effective agent reached at different times in different parts of the host depend upon characters which are open to experimental modification, such as the mode of administration of the agent, but also upon many which are not. The latter may be accommodated by suitable choice or design of agent and include its physiological characters such as absorption, excretion and reabsorption, and biochemical ones such as its activation or inactivation by substances or processes of the host. It is necessary to study these factors, and other undesirable reactions with the host, before correlation of chemotherapeutic efficacy with structure of the agent can be expected. Events in the complete chemotherapeutic system have been referred to properties of its components by observations which include: correlation of the actions of an agent upon the parasite in vivo and in vitro; the reproduction in vitro of synergism and antagonism observed in chemotherapy; the finding of in vitro phenomena associated with drug resistance in vivo; and the type of change in the host associated with success of chemotherapy or with normal recovery from, and resistance to, infection.
BACTERIAL GROWTH
Authors: HINSHELWOOD C. N. 
Published: January 2008

Summary(i) The structure of the bacterial cell is simple: the various regions of enzyme activity may be macromolecular networks of specific pattern which grow by poly‐condensation reactions. Intermediate substrates diffuse from one enzyme to another in the cell, so that the activity of the bacterium is at least in part a sequence of chemical reactions linked both temporally and spatially in definite relations. Various growth phenomena can usefully be looked at from this point of view. A fundamental scheme of enzyme synthesis is considered. (2) The various phases of the bacterial growth cycle are considered. During the lag, among other events, concentrations of diffusible intermediates are built up: these intermediates may be lost from the cell (which accounts for various observations, including an effect of inoculum size on lag). The starting‐point of the reaction series varies with the species of bacterium. When all enzymes are active, and all the intermediates are present with stationary concentration gradients, the logarithmic phase begins. The conditions determining the validity of the logarithmic growth law, the factors governing the setting in of the stationary phase, and the law expressing the decline of the viable population are discussed in the light of experimental data. (3) Cell elongation and cell division are factors separately modifiable by media or by drugs, with resulting changes in morphology. In particular the formation of cells of abnormal length is considered. ‘Life cycles’ are not accepted. (4) The laws expressing the influence of drug concentration on bacterial growth are discussed. Drugs may attack specifically different points in the reaction sequence: they may influence lag and growth rate independently. The action of proflavine on a coliform organism is considered in some detail. (5) The adaptation of bacteria to use new sources or to resist drugs is thought to depend upon modifications induced. in individual cells during growth, and not to be explicable simply by a selectionof substrains. (6) Various groups of experimental facts are described and the hypothesis put forward that certain adaptation phenomena arise from a modification of the relative proportions of different enzymes, occurring during the expansion of the cell substance. The possibility that variants arise from multiple modes of cell division is also considered: change of enzyme balance and multiple modes of division are probably interrelated effects. (7) The spontaneous and induced reversion of drug adaptation is considered. (8) The limits of adaptation and the reason for the stability of the main species characters is discussed.
THE FLORISTIC COMPOSITION OF PRIMARY TROPICAL RAIN FOREST
Authors: RICHARDS P. W. 
Published: January 2008

Summary(i) The tropical rain forest is a formation‐type or pan‐climax. Its outstanding characteristic is the enormous wealth of species of which it is composed. (2) The investigation of the floristic composition of the rain forest presents special difficulties owing to the inaccessibility of the tree‐tops, non‐seasonal flowering and the backward state of taxonomy in tropical regions. For these reasons little definite information has been forthcoming on the subject until recently and the rain forest in each of the main geographical regions has been regarded as forming a vast assemblage of species varying in composition from place to place and not differentiated into distinct forest types comparable to the associations and consociations of temperate forests. (3) The floristic composition can best be studied by counting the trees on sample plots, identifying them first of all by their vernacular names with the help of native ‘tree‐finders’. With sufficient precautions this method can be made to give results of scientific value. (4) Primary lowland rain forest may be either Mixed Forest with numerous dominants or one dominant may form a large proportion of the stand. (5) Mixed rain forests may contain up to 100 species of trees 8 in. diameter and over in a sample plot 400times400 ft. The majority of the species in such a plot are represented by one or very few individuals, the average number of individuals per species (Mischungs‐quotient)for trees 8 in. diameter and over being sometimes as low as 2–7. The evidence suggests that in any one geographical area there is only one mixed association whose composition fluctuates in both space and time. (6) Forests in which one species forms a large proportion of the whole stand are found in all the major tropical regions, but occupy small areas compared with the mixed associations. Some of these single‐dominant types are comparable with the consociations of temperate forest climaxes, while others should probably be regarded as societies of a gregarious species. In South America and Africa the majority of the dominants of consociations belong to the Leguminosae. (7) Most, perhaps all, of these single‐dominant communities occupy special soils or habitats and it is suggested that they tend to be restricted to non‐optimal soils while the mixed association occupies optimum soils. On similar soils in geographically widely separated areas there tends to be a parallel differentiation of edaphic forest types. (8) The single‐dominant forests can probably be regarded as what Braun has termed ‘association‐segregates’. If this is so the tropical rain forest, like the ‘Mixed Mesophytic Forest’ of North America, would consist of undifferentiated climax associations together with association segregates which are consociations, i.e. associations with a tendency to single‐species dominance.I would like to express my gratitude to Mr T. A. W. Davis and Mr T. G. Tutin for communicating unpublished data, and to Dr H. Godwin and Mr T. G. Tutin for kindly reading and criticizing the manuscript.