All contributions should be intelligible to as wide an audience as possible, clearly setting out their novelty, significance and possible application to humans.

Articles and Reviews
Submitted articles are first assessed for relevance to the journal. If deemed suitable they are sent out for peer-review and their abstracts are placed on web soon after receipt, with a disclaimer stating that the corresponding article should not be quoted or discussed until the article is accepted for publication. Authors who do not want their abstract posted online must indicate this on initial submission. Abstracts of papers not accepted for publication are removed from the website.

Peer review is carried out by at least two referees usually within 3 weeks of submission. Accepted papers are published both online a few weeks after acceptance and later in print. The online version is not first proof-read by the author although there is later opportunity to have any serious errors corrected if necessary. The printed version is the definitive proofed copy. A PDF file of the printed version is later placed online for download, usually early in the cover month of the issue in which the article is included. These arrangements permit members of the scientific and medical fraternities to see a wide range of accepted new data at a very early stage online and then in print. All published articles relevant to the journal are archived and available online.

Other items for publication
Letters, commentaries, editorials, short communications, news (no longer than 700 words) and other items are posted on the web immediately after preliminary scrutiny and grammatical editing as necessary. The editors reserve the right to consult referees and make grammatical and/or presentational changes. Proofs of letters and news items will not be sent to authors prior to publication.

1. Materials and methods: Sufficient detail to enable experiments to be repeated, including source company names and addresses, must be supplied. SI units and abbreviations are preferred. If others are used, a conversion factor must be given at first mention.

Manuscript guidelines

1. Materials and methods: Sufficient detail to enable experiments to be repeated, including source company names and addresses, must be supplied. SI units and abbreviations are preferred. If others are used, a conversion factor must be given at first mention.

2. Abbreviations: Restrict to a minimum. Define at first mention in text. Standard units of measurements and chemical symbols of elements need not be defined.

3. Statistics: Procedures and types of analyses must be clearly specified (even where computer programs have been used), referencing publications where necessary to allow readers to ascertain how they were carried out. Large-scale trials should follow the Cochran Principles. Statistical advice can be obtained from Dr D E Walters, Thorpe, The Grip, Linton, Cambridge CB1 6NR, UK (Tel. +44 (0) 1223 891 558; e-mail: dew1@cus.cam.ac.uk) who may require payment for his advice.

4. Reference list: In text, author name followed by year of publication all in round brackets, e.g. (Edwards, 1980; or for multiple authors: Edwards et al., 1980). At the end of the article a reference list in alphabetical order must be given as follows: For books: surname, initials, year of publication, title, publisher, place of publication, number of pages, e.g. Edwards RG 2000 Alternatives in Journal Publishing, The Press, Cambridge, UK. pp. 167. For journals: surname, initials, year of publication, title, journal (not abbreviated), volume, pages (inclusive), e.g. Edwards RE 2000 Beyond multinational publishers. The Editor 4, 45-57. For multiple authors, an example is Cohen J, Levron J, Palermo G et al. 1995 Atypical activation and fertilization patterns in humans. Theriogenology 43, 129-140.

5. Tables: Keep to a minimum and keep simple. Type on separate pages after the reference list. Supply a brief title and number consecutively in arabic numerals in order referred to in text. They should be self-explanatory without reference to the text. Footnotes should be indicated by lower-case letter superscripts; they should not contain extensive experimental detail or discussion.

6. Figures: Keep to a minimum. Number consecutively in arabic numerals in order referred to in text. Figure legends must appear on a separate page within the article file. Define all symbols and abbreviations used in the figure. Axes must be appropriately labelled with each figure in a separate file. Photomicrographs must carry scale bars.

7. Human and animal experiments: These must have been carried out according to the Declaration of Helsinki and the Guiding Principles in the Care and Use of Animals (DHEW Publication, NIH, 80Ð23).

8. Ethics and vested interests: Wherever necessary, ethical approval must be included in the manuscript. This includes approval by Ethical Committees, hospitals, departments and any other place of work. Details of such approval must be provided where necessary. Details of vested interests, e.g. member of company board providing equipment etc., shareholder in such a company, or other forms of investment related to the study in question must be published. Referees are also asked to declare any potential conflict of interest, e.g. financial, academic, personal or political.