bluuebunny/crossref_metadata_2025 huggingface dataset:
Tax Expenditures on Health in Australia: 1960–61 to 1988–89
Authors: Butler J. R. G. , Smith J. P.
Published: January 2008

Commonwealth government tax expenditures arise because departures from the tax structure produce favourable tax treatment of particular types of activities or taxpayers. Such tax concessions can be used in the same way as direct expenditures to give effect to government policies, and in fact are often used as substitutes for direct expenditures. Although estimates of tax expenditures on health in more recent times are readily available, this form of subsidisation of the health sector has not been used heavily since the introduction of Medicare in 1984. It is for the period spanning the 1960s and the 1970s, when tax expenditures were a much more important source of health care finance, that consistent estimates are lacking. This article presents estimates of the revenue cost of income tax concessions for health in Australia over the period 1960–61 to 1988–89 and integrates these estimates into the currently available health expenditure statistics. It is concluded that failure to allow for tax expenditures on health when analysing public expenditures on health in Australia can lead to misleading conclusions about the net fiscal impact of changes in the Commonwealth's health expenditure policy. In particular, the fiscal effect of introducing Medihank in 1975 is significantly lower if account is taken of changes to tax concessions on health occurring at the same time. Likewise, the net cost of the introduction of Medicare in 1984 is overstated by measures based on direct outlays alone.
What Australian Economics Professors Think
Authors: Anderson Malcolm , Blandy Richard
Published: January 2008

In this article we present the results of a recent survey of economics professors in Australia. We found that there is a comfortable measure of consensus in many areas of economic science, including several contentious issues which currently worry policymakers and the general public alike. We show that there is good evidence to suggest that Australian academic economists share a world economic culture with their western European and (to an even greater extent) their American colleagues.

We also asked the professors to share their thoughts on university economics education. There was good consensus that the professors wanted a rigorous classical economics education for their students, but they were not willing to sacrifice breadth: the ideal student, it appears, is one technically competent in economics with a head for the social and political dimensions of the profession. Overwhelmingly, the professors voted the economics department of the Australian National University as the best place for such an education, with those of Melbourne, the University of New South Wales, and Monash, close behind.

Finally, the professors gave their opinions on the understanding of economics by government agencies, business and community groups.
Limitations of the Budget as an Instrument of Macroeconomic Policy in 1992–93
Authors: Adams Philip D. , Dixon Peter B.
Published: January 2008

The major macroeconomic challenge facing the Government is to reduce the unemployment rate without increasing inflation and the current account deficit. The Budget for 1992–93 gave the Government an opportunity to set out its policy for meeting this challenge.

In this article we assess the Budget from a macro‐economic point of view. We ask whether the Government could have done more to address the problem of unemployment.

Our analysis is in two parts. In the first, we answer the question: has the Government made believable forecasts for 1992–93, given its assumptions and the set of Budget policies. In the second part we consider whether, given the Budget assumptions, the chosen policy is the best one.

To answer the first question, we used the COPS short‐run forecasting model (see the Appendix to the article) to obtain projections for 1992–93 under Budget policies and assumptions. These projections are almost identical to those of the Government, prompting a ‘yes’ to the first question. To answer the second question, we used our model to set out the effects of a more stimulatory budget strategy under five different sets of assumptions. These differ with respect to the exchange rate, private investment and wage rates. We find that a more stimulatory policy might help in increasing GDP and employment growth. However, nervousness in the foreign exchange market concerning the PSBR, resistance in the labour market to real wage reductions and sensitivity of private investors to increases in interest rates all combine to make the more stimulatory policy a risky one.
Advancing into the 21st Century: Visions and Challenges Facing the Downunder Economy
Authors: Kasper Wolfgang
Published: January 2008

Long‐term visions serve to focus on essentials for sustained economic and social welfare. We now have to face up to the challenge of globalisation (growing international capital mobility), at a time when we are undoing our historic, self‐imposed protectionism. This also creates new opportunities, in particular in the dynamic Asia‐Pacific economies.

There still is a ‘window of opportunity’ before an aging population will become a dominant problem. In the next 25 years, business will have to cope with high real interest rates and major uncertainties that now surround environmental policies.

If we are to take on these challenges in constructive and beneficial ways, we have to develop an institutional order that enables the utilisation of knowledge by enterprising people. This requires a simple, transparent and reliable legal and regulatory framework, which supports competitive market processes, and the defence of openness to international trade and capital flows against particular interest groups.

It seems plausible that the Downunder economy can grow over the next 25 years at about 3.5 per cent per capita if the right institutional conditions are created. If we fail to do so, a growing share of the capital, the skills and the enterprise made Down‐under will move to offshore locations which encourage a better use of knowledge and capital by enterprising people. This would deprive many of economic opportunity. The central challenge therefore is to develop a system of government and labour relations which makes the Downunder economy internationally attractive.
Global Integration
Authors: Lloyd P. J.
Published: January 2008

This article argues that there are underlying changes in the world economy due to growing integration of the national economies which are more profound than the events in particular commodity markets, and that our national economic policies should be significantly shaped by these changes. Integration is defined in terms of the convergence of prices on international markets. It is occurring in the markets for commodities, factors and technologies. The freeing of trade multilaterally and unilaterally and the formation of regional trading arrangements have all played a part in greater global integration.

Global and regional integration have changed the nature of the international markets in which we trade and require corporations to change their production and marketing strategies. Governments have an increasingly important role in negotiating international and regional agreements and in providing an environment that allows the domestic producers to compete on international markets. There is, however, no need to change the unilateral trading policies of Australia.
Five Examination Answers for Schools: Microeconomics
Authors: Norman Neville R.
Published: January 2008

This article follows a similar format to my contribution on five sample answers on macroeconomics, published in the 3rd quarter I992 issue of this journal. The aim is again to present essays written under pressure, as if an Australian teenager with a good command of the subject had written them. The positive response to the first set of essays suggests there may be value in this approach. As before, I have supplemented my draft with footnote after‐thoughts to explain my strategy and some of the temptations I have sought to avoid. Very often it is important to stop a particular line of argument, or the detail or definition of something, to prevent the essay getting out of balance or straying into what an examiner may brand as 'trivia'. at least in the sense of the question asked. This time I have also added some extended comments on the overall approach to each question.

I have avoided diagrams and data that I would normally use in an academic writing as such. This is mainly because a student would not have the data in the exam room and because a good answer can explain a diagram in the mind without actually drawing it.

Sometimes the question is already structured for you: write notes on each of the following six things, for instance. This can be deceptive, for there will sometimes be a requirement to relate the concepts to each other, or to some defined context. (Eg 'In relation to the Australian economy…')

I have selected five essays that cover different parts of microeconomics and tried to answer in different styles. Some questions call for a good understanding of the principles involved, and if you knew nothing of Australia's situation it would hardly matter. Others call for that knowledge of our industries, their operations and policy aspects bearing on them. As before I consulted no references or data, and some of my recollection may be imperject.

I recall someone saying that if you read anything from anyone who has been through Economics at Cambridge, all the best bits are to be found in the footnotes. That may well be true here.
Academic Economic Opinion in East Asia
Authors: Anderson Malcolm , Blandy Richard , Carne Sarah
Published: January 2008

Surveys of economists' opinions have been reported from around the world over the past two decades, but never (as far as we are aware) from a non‐Western country. This article presents the results of our survey of academic economists drawn from ten East Asian nations.

Respondents gave their views on a number of economic propositions ranging across issues of deregulation, government business enterprises, micro‐economic and labour market reform, income distribution, and attitudes to the market.

Finally, the article reports the results of multidimensional scaling techniques which were used to compare the attitudes of East Asian academic economists toward the market with those of their international colleagues. Overall, we found that while our colleagues in Asia make some allowances for circumstances unique to fast‐growing developing economies, their predilection toward market solutions to economic problems reflects that of their (predominantly) Western training.

Economists in the ‘Tiger’ nations (Hong Kong, Singapore, Taiwan and South Korea) more closely reflect the views of colleagues in the market‐friendly West (especially North America, Australia and Germany) than do economists in the newly emerging (‘non‐Tiger’) nations such as Malaysia, Thailand, Indonesia and the Philippines.
Population Ageing and Social Expenditure in Australia
Authors: Creedy John , Taylor Penelope S.
Published: January 2008

Projections of the social expenditure to GDP ratio indicate the extent of the ‘burden’ of population ageing on future workers and have been used by governments to aid policy decisions in such areas as immigration and superannuation. This article shows that the social expenditure to GDP ratio is heavily dependent on assumptions made about real spending growth, productivity growth, unemployment and participation rates. It produces a framework that makes the assumptions underlying the projections clear and enables the results of changing the assumptions to be easily compared. The projected ratios are significantly higher than those obtained in previous Australian studies.
Planning Retirement Income in Australia: Routes through the Maze
Authors: Atkinson M. E. , Creedy John , Knox D. M.
Published: January 2008

Individual retirees face a daunting task when they consider how best to invest their accumulated superannuation account and non‐superannuation savings. This article highlights the fact that there is rarely an obvious decision in this choice and that the optimal decision depends on a number of factors. These factors include the valuation criterion adopted, the level of benefits, the individual's income level, the means‐tests, the tax rates on income and superannuation benefits and the person's life expectancy. The optimal behaviour at retirement is significantly affected by the individual characteristics of relative lifetime earnings and post‐retirement rates of mortality.
Should AFTA and CER Link?
Authors: Lloyd P. J.
Published: January 2008

This article examines the logic of the link between the ASEAN Free Trade Area (AFTA) and the Closer Economic Relations (CER) regional trading arrangements which was mooted by the Thai Prime Minister in 1993. AFTA and CER are the only two regional trading arrangements in the East Asia/West Pacific region and both are advancing to a high degree of regional integration. This article argues that there are undoubted gains to be had from an AFTA‐CER link by itself which includes reciprocal trade liberalisation as well as trade facilitation. Both groups of countries would benefit from freer trade between them and both have a lot to learn from the experiences of the other regional trading arrangement. However, this link will be redundant if the Bogor Declaration of the APEC is implemented after the Osaka meeting of APEC Leaders in November 1995. If, instead, multilateral trade liberalisation through the World Trade Organisation and APEC falters, an AFTA‐CER link becomes an important possibility.
Real Business Cycle Models: An Introduction
Authors: Crosby Mark , Otto Glenn
Published: January 2008

In this article we present a simple real business cycle (RBC) model, in order to show that these models capture many of the features of business cycles in the real economy. While these models are very abstract, we argue that they are a useful way of thinking about the macro‐economy. RBC models have also been influential in refocusing attention on supply issues in macroeconomics, after a long postwar focus on aggregate demand management in Australia and most other western economies. Policies such as structural reform and labour market reform are clearly aimed at influencing the supply side of the economy and productivity, and can be understood within the framework of RBC theory. RBC models have developed rapidly recently, yet there remains a good deal of misunderstanding about the methods and aims of these models. In this article we present a review of the literature and examine a simple model, using graphical techniques, to clarify some issues. We also argue that these models, while having limitations, have caused a fruitful re‐examination of supply issues in economics, after the almost exclusive focus on aggregate demand in macroeconomics until the late 1970s.
Private and Social Rates of Return to Secondary and Higher Education in New Zealand: Evidence from the 1991 Census
Authors: Maani Sholeh A.
Published: January 2008

Abstract

With significant increases in the demand for higher education in New Zealand since the 1980s, the question of the size of the returns to investments in education has been of significant interest. Despite this interest, studies have been few in number and based on aggregated measures from the 1960s to 1981. This study is the first to utilise micro‐level data from the 1991 New Zealand Census. The study employs and compares the conventional methods of regression earnings functions, and internal rate of return analyses of private and social rates of return. The results indicate that returns to education are economically significant, at rates that are higher for females, even when adjusting for hours of work and female labour force participation differences. The returns are subject to diminishing returns, and social rates of return are 1 per cent to 3 per cent lower than private returns—a result that is consistent with those of OECD countries, but among the smaller differences by international standards.
Forward Planning and Stability of the Australian Migration Program
Authors: Clarke Harry
Published: January 2008

Should the Australian immigration intake be forward‐planned and, if so, should the resulting intake be numerically stable through time? There are sound reasons for anticipating the effects of current intakes on future intakes and for basing current intakes on Australia's long‐term national objectives. These policy requirements imply a case for forward planning but not the need for a stable intake. Appropriately designed numerically unstable intakes are preferable to stable intakes because instability, while introducing adjustment costs, avoids more significant losses due to reduced selectivity in the entry mix.
Of Grand Prix and Circuses
Authors: Gans Joshua S.
Published: January 2008

The public competition between states for major events such as the Indy Car, Formula One and Motor Cycle Grand Prix is analysed from a simple game theoretic perspective. It is demonstrated that such competition is, in general, harmful to the states themselves. Competition leads to greater payments for events to promoters, distortions in the type of event eventually held and, sometimes, the wrong state holding the event. These considerations give a prima facie case for central coordination of event attraction to Australia.
A Cost Function Analysis of the Australian Transportation Equipment Industry
Authors: Truett Lila J. , Truett Dale B.
Published: January 2008

This article investigates the existence of economies of scale and input cross and direct price elasticities of demand in the Australian motor vehicle industry. Our estimated cost elasticities were less than one (consistent with economies of scale), but not significantly less than one at the 10 per cent level for two versions of the model. However, the estimated cost elasticity was significantly less than one at approximately the 2.5 per cent level for a third. Thus, these results give some credibility to the infant industry argument for continued assistance to the Australian transportation equipment industry. A four‐input model separating domestic and foreign intermediate goods inputs suggests that while restrictions on imported components may have given some short‐run relief to the domestic components industry and increased the demand for labour domestically, they decreased the demand for domestic capital. Although the infant industry argument could support short‐run protectionist policies for the industry, it appears that such policies regarding the Australian motor vehicle industry must be designed carefully with a specified phase‐out period if long‐term adverse results are to be avoided.
SUR L'HISTOPHYSIOLOGIE DES ANNEXES FŒTALES DES MAMMIFÈRES
Authors: GÉRARD Par POL
Published: January 2008

The histophysiology varies in the three different types of placenta, namely the epitheliochorial, the endotheliochorial, and the haemochorial.

The histophysiology of epitheliochorial placentas is almost unknown. In the case of the other two types, researches have been made which, although fragmentary, allow of the following conclusions being deduced. In endotheliochorial placentas the hypertrophied uterine glands contribute considerably to the nutrition of the embryo. The remainder of the substances, at the expense of which embryonic development is carried out, come from the maternal blood and are absorbed in the region of the placenta by the trophoblastic ectoderm. This absorption is selective: when certain soluble substances are injected into the maternal circulation, some are seen to pass into the embryo, others are stopped by the trophoblast, in which they accumulate.

In the case of haemochorial placentas the uterine glands supply little material for embryonic development. The embryotrophic substances are derived from two sources. One of these is the maternal cells, which become filled with reserve inclusions (decidual cells) and are absorbed by the trophoblast. A veritable maternal placenta is thus formed, which, in certain species, can change its situation in the course of gestation, being at first localised in the basilar deciduum, then rapidly absorbed, and finally reformed in the region of the mesometrium. The second source is the maternal blood which directly bathes the foetal trophoblast. The latter partially fixes colouring matters injected into the mother, while allowing a certain amount to diffuse into the embryonic mesenchymatous tissue of the placenta. Here the maternal blood, comes into contact with the embryonic vessels, the endothelium of which acts as an impassable barrier for the dyes, since these are not found in the embryo itself, although they pass into the external coelom. In rodents the umbilical vesicle, by means of its vitelline endoderm, acts as an energetic resorber and contributes to the nutrition of the embryo. In the rodents showing inversion of layers the endoderm of the umbilical vesicle is differentiated differently on the placental face and on the inner layer of the umbilical vesicle. Physiological differences correspond to these morphological differences.
CHEMICAL HETEROGONY AND THE GROUNDPLAN OF ANIMAL GROWTH1
Authors: NEEDHAM JOSEPH
Published: January 2008

1. In the preceding pages the application of the concept of heterogony to the chemical changes in growing Metazoa has been discussed.

2. A number of concrete examples have been brought forward which seem to indicate a uniformity of chemical heterogony in widely different organisms.

3. Hence it is suggested that there exists a fundamental chemical ground‐plan of animal growth, capable of very varying expression in space‐time.
THE HAEMOCYANINS
Authors: REDFIELD ALFRED C.
Published: January 2008

As yet we know comparatively little about haemocyanin. especially with regard to its relation to oxygen. It is a matter which would well repay investigation to determine whether it has the remarkable properties which haemoglobin has in this respect. properties which are at present unique. (Bayliss, Principles of General Physiology, 1915.)

The haemocyanins are proteins combined with a prosthetic group consisting of a complex copper salt of a sulphur compound and a polypeptide. The physical and chemical properties of haemocyanin are largely due to its protein nature, and the specific differences between the haemocyanins of different groups of animals result largely from the differences in the protein part of the molecule. The combination of haemocyanin with oxygen and the characteristic change in the absorption spectrum which results are, on the other hand, properties of the prosthetic group. The haemocyanin combines with oxygen in all cases in proportion to its copper content, one molecule of oxygen being combined by a quantity of haemocyanin containing two atoms of copper. There is some evidence that at least two modifications of the prosthetic group may occur characterising the Crustacea and cephalopods on the one hand, and the gastropods and Limulus on the other. The equilibrium with oxygen may be described by the mass law if it be assumed that under different conditions one, two, or four prosthetic groups must be oxygenated simultaneously in order to form a stable compound and that under certain conditions a mixture of such forms of the protein exist. In general the oxygenation phenomena displayed by haemocyanin differ from those of haemoglobin only in a quantitative sense.

The copper of the prosthetic group is in the cuprous condition but may be oxidised, forming methaemocyanin, by strong agents. Methaemocyanin will combine reversibly with oxygen, forming oxymethaemocyanin. Haemocyanin also combines with carbon monoxide, nitrogen dioxide and with cyanide, forming stable compounds.

The physiological function of haemocyanin as a respiratory pigment is well established in the case of the cephalopods. Some correlation exists between the activity of various animals, the oxygen capacity of the blood, and the pressures of oxygen under which the haemocyanin becomes oxygenated.
CHEMICAL REGULATION AND THE HORMONE CONCEPT
Authors: HUXLEY JULIAN S.
Published: January 2008

Summing up, our general conclusions are therefore as follows:

1. The term hormone can only be defined biologically, as a chemical substance produced by one tissue with the primary function of exerting a specific effect of functional value on another tissue.

2. This biological definition is justifiable, and likely to prove of permanent value.

3. All gradations exist between hormones as above defined and substances which exert their specific effect on the same tissue by which they are produced. The term activator is proposed to cover these substances as well as hormones.

4. All gradations exist between hormones and activators above defined, and substances produced as by‐products of metabolism (normal or pathological) which then exert effects (of specific functional or of accidental nature) on the other tissues (or on the same tissue). For these the term parahormone (Gley) or para‐activator will serve.

5. Activators may be classified according to their means of transport: (a) Local activators, no transport, (b) Distance activators or hormones, with transport; (i) diffusion hormones, transport by diffusion, (ii) circulating hormones, transport by the blood stream or lymph.
GROWTH, TIME, AND FORM
Authors: GLASER OTTO
Published: January 2008

1. The equation, log w=k. log (2t+ 1) +C is a peculiar modification of the compound interest law. It is derived from growth in fresh weight of chick embryos, and applies to fresh weights of the domestic fowl and of the smaller as well as larger domestic mammals. For the dairy cow, weights are calculable from time, with an error of less than 1 per cent.

2. The circumstances under which k can remain constant are analysed. A period of constancy is called a stanza of growth. Stanzas for the whole and the part or for different parts, may or may not be synchronized. The conditions under which a particular category terminates a stanza of growth can be foreseen from the circumstances that assure the constancy of k.

3. In the category of fresh weight, water is the quantitatively dominant entity. The equation describes also other categories: (a) when dominated by specific entities; (b) when their quantitative organization is constant; (c) when applied to specific isolated chemical substances. This and the relatively independent behaviour of unit categories or entities makes it possible to calculate the amount of calcium moved from the shell by the developing embryo; and to account for the upward swing of dry substance after the ninth day of incubation. The only specific postnatal category dealt with, is “antlers” in deer. Such analysis is possible since, under certain conditions, the time “lost” in intermittent growth, becomes irrelevant.

4. The effects of temporal errors introduced by faulty timing are discussed and illustrated. According to the equation, any finite value of k automatically provides for the termination of growth at infinity. Actual cessation is mathematically precocious, and implicates heterogony.

5. By means of y=bxk, the functional relation between organic mass and time can be extended to include also form, since the heterogonic constant

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or

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6. Heterogonous growth may be considered as imposed on a system in certain respects practically or actually isogonous at origin. Parallel rates whether limited to a single stanza or surviving several are designated according to the number of rates involved, as isogonic diads, triads, etc., and are responsible for the maintenance of the compatibilities during heterogonic growth.

7. Among the heterogonic relationships is one that cannot at all times conform to y= bxk, since it involves the mixture “dry substance”. Excepting the frog tadpole prior to metamorphosis, the ratio of water to dry substance falls during growth and stabilizes at maturity. Where growth is indeterminate, stabilization occurs at a level higher than for determinate growth.

8. Certain kinetic implications of the water to dry substance ratio suggest that growth, maintenance, and senility, are related to changes in the rates of the several metabolic transactions. This hypothesis is tested by an appeal to data on the frog, the white rat, man, and a variety of crop plants. In all the plants the onset of senility demonstrably associates with a fall of the water to dry substance ratio below the maintenance level of maturity.
ENZYME VARIATION IN MICRO‐ORGANISMS
Authors: YUDKIN JOHN
Published: January 2008

The increase in enzyme content in micro‐organisms may be classified according to the type of substance responsible for the increase. First, as has been suggested by Jacoby, the substance may be necessary to the cell as a “brick” for the building up of the enzyme molecule. Secondly, the substance may be the substrate of the enzyme or some closely related compound. A substance in this class may act either directly on the individual cell or as a selecting agent during growth of cells in which the enzyme has appeared as a mutation. Examples of direct chemical interaction between cell and substrate (adaptation) are the hydrogenlyase of Bact. coli and the galactozymase of yeast; examples of mutation and selection occur amongst organisms of the Bact. coli mutabile type.

As would be expected, when organisms possessing a newly acquired enzyme are grown in the absence of the substrate, enzymes arising by adaptation are readily lost whilst enzymes arising by mutation and selection tend to be permanent.

It would also be expected that the former type of enzyme production would occur in the absence of cell division; for natural selection to operate, however, cell division is essential. Many unsatisfactory attempts have been made to show the dependence or otherwise of certain examples of enzyme production on cell division, such as the study of enzyme production in the presence or absence of suitable growth substances or of poisons. By counting experiments, however, it has been clearly shown that, in the two examples of adaptation quoted, enzyme production occurs in the absence of cell division.

Although enzyme production has been obtained in non‐dividing (but untreated) cells, it has not yet been found possible to obtain it in cells which have been rendered non‐viable, that is, incapable of dividing. It would be of interest if such poisoned cells would be found still able to produce the adaptive enzyme, but it is necessary to define carefully the meaning of living cell and growth in relation to micro‐organisms before deciding on the dependence of enzyme production on cell viability or cell growth.

Apart from general statements of a teleological nature, the literature contains no general theory of adaptive enzyme production. The “mass‐action” theory of enzyme formation here developed explains the majority of the known facts, is in contradiction with none of them, and allows several deductions to be made which are capable of being tested experimentally.
THE CO‐ORDINATION OF VERTEBRATE MELANOPHORE RESPONSES
Authors: WARING H.
Published: January 2008

1. Two classes of melanophore responses to light can be distinguished:

(a) A primary, direct or non‐visual response involving the expansion of the melanophores in light and their contraction in darkness. This non‐visual response may be a co‐ordinated response or the melanophore may be an independent effector.

(b) A secondary or visual response when the melanophores contract if the visual field is coincident with a light‐scattering field, and expand if the animal is exposed to superior illumination in surroundings which do not reflect or scatter light coming from above.

2. Co‐ordination of melanophore responses in elasmobranchs and Amphibia is by means of pituitary hormones circulating in the blood.

3. A direct nervous control of melanophores has been superimposed on the more archaic humoral mechanism to a varying extent in different genera of teleosts. Sufficient is now known of this group to formulate tentatively a general scheme applicable to all forms, according to which the two components–humoral and nervous–are developed to a greater or less extent in various genera.

4. Co‐ordination of melanophore responses in some reptiles is solely humoral. In others only nervous agencies have been discovered. Insufficient data are available to construct a scheme showing the phyletic relationship of the two systems between the members of the group.

5. The kind of evidence that is acceptable for the existence of the various co‐ordinating systems is discussed.

6. The merits of the bihumoral, double innervation and neuro‐humoral hypotheses are discussed.

7. An evolutionary scheme is appended which may tentatively be taken to indicate that direct nervous control is phylogenetically a later development than humoral control.
BIOLOGICAL METHYLATION
Authors: BACH S. J.
Published: January 2008

The enzymatic methylation or demethylation of naturally occurring compounds represents significant metabolic processes which have gained additional interest since the discovery of a mechanism by means of which methyl groups can be transferred from one compound to another.

The capacity to transfer methyl groups is confined to a fewN‐and S‐methylated compounds; methyl groups linked to C atoms, however, have not been found to be transferable but are known in some cases to be oxidized. OtherN‐methylated compounds, such as sarcosine, the methylated ammonium bases, the α‐ and γ‐betaines of amino‐acids other than glycine, are unable to take part in the methyl exchange in either direction, but are oxida‐tively demethylated by the organism or excreted unchanged. Choline, methionine, and to a lesser degree betaine, play a major part in transmethylation; these compounds are needed for the maintenance of growth and for the prevention of fatty infiltration of the liver, kidney haemorrhage, liver cirrhosis, or perosis. Since choline can methylate homocysteine to methionine in the organism and conversely methionine and betaine are able to supply methyl groups for the methylation of ethanol‐amine to choline, a system of continuous interchange of methyl groups is established and a ‘pool’ of labile methyl groups is formed. This ‘pool’ also acts as a source of methyl supply for other compounds such as creatine, methylnicotinamide, anserine and possibly others, but these latter compounds have not been shown to act as ‘methyl donors’. The role of glycine and of methylated purines as methylating agents is controversial.

The liver is the main site of methylation, though kidney and muscle tissue were found to catalyse methylation in a few cases. The chemical mechanism of methylation and demethylation has not yet been clarified. Oxidation prior to demethylation is believed to take place in the case of methionine. A methyl synthesis from unmethylated sources is possible but not probable; as a consequence methylated compounds with labile methyl groups must be regarded as essential dietary factors.

The physiological significance of the numerous naturally occurringN‐methylated compounds is further enhanced by their pharmacological effects and by their relationship to hormones. The latter manifests itself in the preponderant occurrence of many methylated compounds at the sites of hormonal activities connected with reproduction, and conversely by the alleged effect of some hormones on methylating activities. Thus it is not unreasonable to picture an influence of methylating reactions on the regulatory activities of hormones leading in pathological cases to a derangement of the hormonal balance and possibly to abnormal growth conditions such as malignancy.

I wish to express my gratitude to Dr E. M. Crook, Kothamsted Experimental Station, for reading the manuscript and for valuable criticism.
BACTERIAL VIRUSES OR BACTERIOPHAGES
Authors: DELBROCK M.
Published: January 2008

(i) The following factors are held to be chiefly responsible for recent progress in the field of bacterial viruses: (a) the introduction of ‘one‐step growth experiments’, (b) the concentration of attention on a small group of bacterial viruses, (c) the proof that virus‐resistant mutants originate independently of the presence of virus, (d) the application of the electron microscope. (2) Types of virus morphology, as revealed by the electron microscope, are described. The virus particles of any one strain are of uniform size and shape. Many strains show a ‘head‐and‐tail’ structure. Sizes between 45 and 100 mμ have been found. (3) Classification of a group of seven viruses by serological cross reactions agrees perfectly with classification by morphology. (4) A method for determining the origin of mutations of bacteria from virus sensitivity to virus resistance is outlined. There is evidence that the classification of viruses by cross‐resistance tests is of little value in establishing natural relationships between viruses. (5) The phenomenon of ‘lysogenesis’ is discussed, and certain ambiguities in its definition are pointed out. (6) The physiological basis of resistance of a bacterial strain to the attack by a specific virus is discussed. Such resistance is generally coupled with failure on the part of the bacteria to fix the virus in question by adsorption. Evidence shedding a new light on the process of adsorption is reported. (7) Bacterial viruses can mutate in such a way that their host range is altered. These mutations occur during the multiplication of the virus in its host. (8) The technique and terminology of ‘one‐step growth experiments’ are briefly described. (9) When a bacterium is attacked simultaneously by several virus particles of the same strain or of different strains the bacterium reacts as if it had been attacked by only one particle (mutual exclusion effect). A detailed study of this phenomenon has led to the assumption that the membrane of the bacterium becomes impermeable to other virus particles after one particle has entered the cell (penetration hypothesis). The excluded virus particles may affect the yield of virus of the successful type (depressor effect). (10) The adaptation of the technique of the ‘one‐step growth experiment’ to biochemical studies of virus multiplication is described. (n) The controversies regarding the nature of bacterial viruses are briefly touched upon, particularly with reference to the evolutionary standing of these viruses. (12) It is pointed out that a thorough study of bacterial viruses may lead to a better understanding of all types of viruses.
EXCRETION IN THE OLIGOCHAETA
Authors: BAHL KARM NARAYAN
Published: January 2008

Oligochaete nephridia are now classified into holonephridia and meronephridia; the former are large and occur as a pair per segment, while the latter are small and are numerous in each segment. The meronephridia are derived from holonephridia by a process of branching and multiplication either at an early or a late stage of development. The tufted nephridia are either incompletely branched holonephridia or meronephridia secondarily grouped together. The two kinds of nephridia are further distinguished as open or closed according as they possess or lack an internal funnel, and still further as exonephric or enteronephric according as they discharge their excretory products to the exterior or into the gut. The holonephridia are almost all open and exonephric; closed holonephridia have been found only in one form, and in one form alone are the holonephridia only incipiently enteronephric. But it is the meronephridia that exhibit the greatest variation in number and size as well as form and disposition, leading to a progressive and divergent specialization in the Megascolecidae, the largest family of the Oligochaeta. As many as ten kinds of meronephridia are met with. The enteronephric system in six genera shows various stages of development from simple segmentally separate units to a single unified and elaborate system of the enteronephridia of the whole of the intestinal region. In one genus the meronephridia are known to be incipiently enteronephric.

An account of the process of excretion is given. Analyses have been made of the urine, coelomic fluid and blood of Pheretima. The excretory substances are ammonia, urea and creatinine; they are initially formed in the body wall and gut wall, and are thence taken up both by the coelomic fluid and blood, which pass the excretory products to the nephridia for elimination to the exterior. The mechanism of nephridial excretion has been analysed into processes of filtration, reabsorption and tubular secretion. The initial nephridial filtrate consists of blood‐plasma minus the colloids, together with the coelomic plasma, but it is modified during its passage down the nephridial canal, as there is a large scale reabsorption of useful substances. Glucose and amino‐acids are completely reabsorbed, while PO C1, Na, K and creatinine are reabsorbed extensively along with water. The urine is really a protein‐free filtrate, but measurable quantities of protein find their way into it, probably from the mucus secreted by the worms during the process of collection. The brownish granules in the ciliated middle tube of nephridia are coloured by a haem pigment. The role of the nephridia in osmotic regulation has been determined by measurement of the depression of freezing point of blood, coelomic fluid and urine and by a comparison of the concentration of various substances in these fluids. The earthworm maintains a steady state like a freshwater organism. The adaptive significance of the enteronephric system is to enable Phcretima to conserve much of its water which is to a great extent returned to and reabsorbed by the intestine.
THE STRUCTURE OF GLYCOGENS
Authors: BELL D. J.
Published: January 2008

1. The usual criteria for identification of glycogen are discussed. It is pointed out that these can be applied equally well to amylopectin and α‐amylodextrin. Numerous so‐called glycogens in plants and micro‐organisms may not be chemically identical with animal glycogens, which may quite well vary among themselves.

2. Mention is made of the methods of isolation and purification. It is considered that precipitation by acetic acid gives the purest material in that nitrogen and phosphate can be eliminated, in many cases entirely.

3. The limitations of the end‐group assay are discussed. This method reveals the sole fact that all glycogens are built up from ‘unit chains’, but gives no information as to the detailed structure of these chains. It is, therefore, not possible to say whether glycogens from different sources are chemically the same or not.

4. A description is given of the difficulties in attempting to analyse glycogens from the aspect of determining the nature of the linkage uniting the unit chains. The suggestion is made that information to this end will have to be obtained by use of stepwise enzymic degradation of the polysaccharide.

5. The latest work on molecular weights is summarized. There is considerable variation according to the type of source from which the glycogen has been isolated. This work is the first indication that there are at least physical differences between glycogens.
THE DEVELOPMENT AND FATE OF THE CORPUS LUTEUM IN THE VERTEBRATE SERIES
Authors: HARRISON R. J.
Published: January 2008

1. Published descriptions of the development of the corpus luteum show that the majority of the luteal cells are derived from the granulosa cells.

2. In the vertebrates, other than mammals, the development of a corpus luteum does not appear to be associated solely with viviparity.

3. The fate of the theca interna cells varies greatly, even in closely related species.

4. The theca interna cells may remain in groups at the periphery of the gland, or they may invade the developing corpus luteum and either: (a) disappear entirely a few days after ovulation, (b) become indistinguishable from the granulosa cells, or (c) possibly revert to fibroblasts.

5. The function of the theca interna or theca‐luteal cells in the mature corpus luteum is unknown. It is, however, possible that they secrete oestrogen.

6. The blood vessels of the corpus luteum are derived from the theca interna plexus of capillaries; the corpus luteum is well vascularized by the time that implantation occurs.

7. The connective tissue of the corpus luteum is believed by many authors to be derived from theca interna cells that have reverted to fibroblasts. In the Artiodactyla and in Macaca, and possibly in other animals, there is evidence that the endothelial cells give rise to the reticular framework.

8. The corpus luteum is generally fully developed by the time of implantation of the blastocyst.

9. The appearance of the vacuoles in the luteal cells of pregnant mammals is not necessarily indicative of impending cessation of function or of degeneration. Such vacuolation may mark a ‘resting period’ as in those animals in which implantation is delayed, or a ‘transition period’ during which the placenta is becoming established structurally and functionally.

10. The time of appearance of retrogressive changes in the corpus luteum of pregnancy in any species is probably related to the degree of activity of the placenta in that species and to the prolactin level in the anterior pituitary.

11. Accessory, aberrant and other atypical forms of corpora lutea have been reported in the macaque, the tree porcupine and the mare.