Lesson Plan — The Disease They Couldn't Catch

Suggested grade band: 9-12 (high school) and introductory undergraduate. Cross-curricular: Biology, AP Biology, AP U.S. History, Public Health, Psychology, History of Science.

Suggested duration: 50-minute single class, with optional follow-on extension.

Overview

In 1914, a public-health physician named Joseph Goldberger was assigned to investigate a rash that had been killing tens of thousands of Americans every year in the rural South. The medical establishment had decided pellagra was infectious. Goldberger demonstrated, by observation, by controlled experiment at a Mississippi prison farm, and finally by deliberately ingesting and injecting himself with samples from active patients, that the disease was nutritional. It still took another twenty-three years before Conrad Elvehjem at the University of Wisconsin identified the specific missing molecule — niacin. This week, Nature Genetics published a paper from McGill University and the Douglas Institute pinpointing two specific brain-cell types altered in major depression. The lesson uses the two stories together to teach the structure of how science actually closes in on a disease: not in a single leap, but in three stages — pattern, cause and molecule — which can be separated by decades of treatment-without-explanation.

Learning Objectives

By the end of the lesson, students will be able to:

1. Distinguish three sequential layers of biomedical understanding for any disease: pattern (what is it), cause (what produces it) and molecular mechanism (which specific molecule, gene or cell).

1. Describe Joseph Goldberger's evidence chain for pellagra (institutional non-staff observation, Rankin Prison Farm dietary experiment, the 1916 filth-party self-experiments) and explain what each piece of evidence ruled out.

1. Define pellagra clinically (the four Ds: diarrhoea, dermatitis, dementia, death) and explain why its dementia symptom led to widespread misclassification of pellagra patients as mentally ill.

1. Compare the historical state of pellagra knowledge in 1914-1937 with the current state of major-depression knowledge: medications that work without a fully specified mechanism, and now (April 2026) a cell-level identification.

1. Write a short evidence-based response to the question: "When is a treatment worth using if its mechanism is unknown?"

Before Reading (5-10 minutes)

Open with two warm-up prompts on the board. Students answer with one sentence each:

• If a treatment works but you do not know why, is it medicine or magic?

• Name a disease that you think we now understand at the level of which exact molecule is missing or wrong. Then name one that we do not.

Hold the second answer in reserve. Many students will name diabetes, scurvy, or sickle-cell as understood, and depression, ADHD or autism as not. The lesson will return to that line.

During Reading (20 minutes)

Distribute the story. Ask students to annotate three things in the margin as they read:

• ★ next to any specific number that surprises them.

• ? next to any claim they would want to verify against a primary source.

• ! next to the moment in the historical story that they think is the equivalent of the McGill paper.

Pause halfway (after the description of Goldberger's filth parties) and ask the room: what would have happened to Goldberger's career if any of the seventeen guests had developed pellagra?

After Reading (15 minutes)

Group discussion using these prompts in order:

1. The story argues that disease knowledge typically advances in three steps: pattern, cause, molecule. Apply that frame to one disease the class has studied (e.g. tuberculosis, AIDS, type 1 diabetes) and identify what year each step was reached.

1. Goldberger could prove what pellagra was not (infectious) in 1916, but could not prove what it was in molecular terms until 1937, eight years after his death. Why is it scientifically harder to identify the specific missing molecule than to identify a general cause?

1. The story closes with the line, "We know the room. We do not yet know the food." What treatment changes do you think might come from knowing the cell type but not yet the molecule? What treatment changes have to wait?

1. Pellagra dementia put thousands of poor southerners in mental asylums for decades. Are there diseases today that we are likely to be misclassifying as something other than what they will eventually be shown to be?

Activity Set

Bell-Ringer (5 minutes)

Project a slide with three diseases per row and four columns labelled "Pattern recognised", "Cause identified", "Molecular mechanism", "First effective treatment". Students fill in the approximate year for each cell, working from memory and a brief handout of dates.

Suggested rows:

• Scurvy

• Pellagra

• Major depression

• Type 1 diabetes

The exercise is meant to expose how unevenly the four columns can be filled in, and how the year-of-first-effective-treatment can precede or follow the year-of-mechanism.

Single Class Activity: The Filth-Party Defence (30 minutes)

Divide the class into two groups. One group is a 1916 medical board investigating Goldberger and considering revoking his licence after the filth parties. The other group is Goldberger's defence. Each group has fifteen minutes to prepare, then five minutes per side to present.

Constraint: both sides must use only the evidence available in 1916 (no niacin-deficiency knowledge from 1937, no modern epidemiology). The exercise is meant to get students to practise reasoning from the evidence the historical actors actually had.

Extension Activity: A Letter from 2049 (homework, 30 minutes)

Students write a 250-word letter, dated 27 April 2049, to the McGill team that published the 2026 Nature Genetics paper. The letter must:

• Tell them what was discovered between 2026 and 2049 about the molecules involved in their two depression cell types.

• Identify, by name, at least one researcher who eventually did the molecular work.

• Avoid the words "vindicated", "obviously" and "of course".

• End with a question the writer would have wanted to ask the McGill team in 2026.

Primary Sources for Further Investigation

• Joseph Goldberger, "The Etiology of Pellagra: The Significance of Certain Epidemiological Observations with Respect Thereto", Public Health Reports 29 (1914), pp. 1683-1686. Goldberger's original published statement of the institutional-observation evidence.

• Joseph Goldberger and George A. Wheeler, "Experimental Pellagra in the Human Subject Brought About by a Restricted Diet" (1915). The Rankin Prison Farm experiment.

• Joseph Goldberger and J. F. Schamberg, "Attempts to Transmit Pellagra to Healthy Volunteers" (1916). The filth-party paper.

• Conrad A. Elvehjem et al., "The Isolation and Identification of the Anti-Black Tongue Factor", Journal of Biological Chemistry 123 (1938). The vitamin identification.

• Anouar Khayachi, Christopher Adam, Daniel Almeida et al. (McGill / Douglas), "Single-nucleus chromatin accessibility profiling identifies cell types and functional variants contributing to major depression", Nature Genetics, 2026. The current week's primary literature.

• Alan Kraut, Goldberger's War: The Life and Work of a Public Health Crusader, Hill and Wang, 2003. Standard biography.

Standards Alignment

Next Generation Science Standards:

• HS-LS1-1 Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

• HS-LS3-1 Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring.

• HS-LS3-2 Make and defend a claim based on evidence that inheritable genetic variations may result from new genetic combinations through meiosis, viable errors occurring during replication, and/or mutations caused by environmental factors. (Adapted: chromatin-accessibility variation in MDD.)

AP Biology:

• ENE-1: Living systems require free energy and matter to maintain order, to grow, and to reproduce. (Pellagra as a deficiency disease.)

• IST-1: Heritable information provides for continuity of life. (NR4A2 transcription factor, gene-regulatory architecture.)

AP U.S. History:

• KC-7.1.III.B Reformers responded to economic instability and social inequality with calls for change. (Pellagra as a disease of Southern poverty; political response to Goldberger.)

C3 Framework for Social Studies State Standards:

• D2.His.4.9-12 Analyze complex and interacting factors that influenced the perspectives of people during different historical eras. (Why southern senators rejected the dietary explanation.)

• D2.His.16.9-12 Integrate evidence from multiple relevant historical sources and interpretations into a reasoned argument about the past.

Assessment Notes

A short formative check (3-5 minutes) at the end of class: In your own words, name a disease for which we currently have a working treatment but no fully specified molecular mechanism. What kind of evidence do you think will be needed before that mechanism is identified? Collect responses. Look for evidence that students can think clearly about the difference between "we know it works" and "we know why it works".