How to write and publish a scientific paper - Barbara Gastel, Robert A. Day 2022

Correct form and grammar
How to write the materials and methods section
Preparing the text

Do not make the common error of including some of the results in this section. There is only one rule for a properly written materials and methods section: Enough information must be given so that the experiments could be reproduced by a competent colleague.

A good test (and a good way to avoid rejection of your paper), is to give a copy of your finished manuscript to a colleague and ask whether they can follow the methodology. In reading about your materials and methods, your colleague might well notice an error that you missed simply because you were too close to the work. For example, you might have described your distillation apparatus, procedure, and products with infinite care—but then neglected to define the starting material or to state the distillation temperature.

Mistakes in grammar and punctuation are not always serious; the meaning of general concepts, as expressed in the introduction and discussion, can often survive a bit of linguistic mayhem. In materials and methods, however, exact and specific items are being dealt with, and precise use of English is a must. Even a missing comma can cause havoc, as in this sentence: “Employing a straight platinum wire rabbit, sheep, and human blood agar plates were inoculated.…” That sentence was in trouble right from the start because the first word is a dangling participle. Comprehension was not totally lost, however, until the author neglected to put a comma after “wire.”

Authors often are advised, quite rightly, to minimize the use of passive voice. However, in the materials and methods section—as in the current paragraph—passive voice often can validly be used, for although what was done must be specified, who did it is often irrelevant. Thus, you may write, for example, “Mice were injected with …” rather than “I injected the mice with …,” “A technician injected the mice with …,” or “A student injected the mice with.…” Alternatively, you may say, “We injected …,” even if a single member of the team did that part of the work. (Although the belief persists that journals prohibit use of first person, many journals permit and even encourage use of “I” and “we.”)

Because the materials and methods section usually gives short, discrete bits of information, the writing sometimes becomes too condensed, with details essential to the meaning omitted. The most common error is to state the action without, when necessary, stating the agent of the action. In the sentence “To determine its respiratory quotient, the organism was …” the only stated agent of the action is “the organism,” and we doubt that the organism was capable of making such a determination. Here is a similar sentence: “Having completed the study, the bacteria were of no further interest.” Again, we doubt that the bacteria “completed the study”; if they did, their lack of “further interest” was certainly an act of ingratitude.

“Blood samples were taken from 48 informed and consenting patients … the subjects ranged in age from 6 months to 22 years” (Pediatr. Res. 6:26, 1972). There is no grammatical problem with that sentence, but the lack of detail leaves the reader wondering just how the 6-month-old infants gave informed consent.

And, of course, always watch for spelling errors, both in the manuscript and in the proofs. We are not astronomers, but we suspect that a word is misspelled in the following sentence: “We rely on theatrical calculations to give the lifetime of a star on the main sequence” (Annu. Rev. Astron. Astrophys. 1:100, 1963). Although they might have been done with a flourish, presumably the calculations were theoretical, not theatrical.

Be aware that a spell-checker can introduce such errors and therefore cannot substitute for careful proofreading. One recent example: A spell-checker converted “pacemakers in dogs” to “peacemakers in dogs.” We have known some dogs that could benefit from peacemakers, but we rightly suspected that this wording was not intended in writing about canine cardiology.