"Figure 2.84: Endogenous normal prion protein (PrPc) is converted into the disease-causing form (PrPsc) when it encounters this variant form of the protein. Left: (c) Rice University. OpenStax Microbiology. CC BY 4.0. https://openstax.org/details/books/microbiology . Right: Modification of work by USDA/Dr. Al Jenny. Public Domain. https://commons.wikimedia.org/wiki/File:Histology_bse.jpg Figure 2.85: Creutzfeldt-Jakob disease (CJD) is a fatal disease that causes degeneration of neural tissue. Left: modification of work (c) Dr. Laughlin Dawes CC BY 4.0. Top Right: Modification of work (c) Suzanne Wakim. CC BY 4.0. Bottom right: modification of work by Centers for Disease Control and Prevention. Public Domain. Figure 2.86: The steps for confirming that a pathogen is the cause of a particular disease using Koch’s postulates. (c) Rice University. OpenStax Microbiology. CC BY 4.0. https://openstax.org/details/books/microbiology . Figure 2.87: A graph like this is used to determine LD50 by plotting pathogen concentration against the percent of infected test animals that have died. (c) Rice University. OpenStax Microbiology. CC BY 4.0. https://openstax.org/details/books/microbiology ."