diascope

noun

di·​a·​scope ˈdī-ə-ˌskōp 

: a plate of glass pressed against the skin so as to expel the blood from a part and show anatomical changes

diascopic

ˌdī-ə-ˈskäp-ik 

adjective

diascopy

dī-ˈas-kə-pē 

noun

plural diascopies