Final answer:
The problem with measuring skin thickness from cadavers in the 1920s and 1930s was that the individuals who donated their bodies may not have been representative of the general population.
Step-by-step explanation:
In the 1920s and 1930s, interest in skin thickness led to measurements being taken from cadavers of homeless and people who had donated their bodies to science. However, the problem with this approach was that the individuals who donated their bodies for research purposes may not have been representative of the general population. This means that the measurements taken may not accurately reflect the average skin thickness of the entire population.