What is the name of the skin layer injected during tuberculosis skin tests in cattle?

The correct answer is the dermis, which is the layer of skin that is injected during tuberculosis skin tests in cattle. This layer contains a rich supply of blood vessels, nerves, and immune cells, making it an ideal area for conducting such tests. The dermis lies beneath the epidermis and contains essential components for immune response, such as lymphocytes, which are important for testing reactions to infections like tuberculosis.

When the test is administered, the injected material—the tuberculin—needs to be deposited at a depth where these immune cells can quickly recognize it and respond if the animal has been sensitized to the pathogen. This is why the dermis is targeted instead of the outer epidermis, which mainly acts as a protective barrier and does not have the necessary infrastructure for immune response. The subcutaneous tissue, on the other hand, lies deeper than the dermis and is not typically involved in this specific test.