A Gallic affair: the case of the missing itch-mite in French medicine in the early nineteenth century.

never demonstrated.1 The itch (in French "la gale") is a disease characterized by violent itching, pimples and scabs on the skin. Today it is accepted that the itching is due to an insect, the sarcoptes, burrowing tunnels into the dermis in order to deposit its eggs, cutting through both the dermis and the small vessels in its path. The tissue reacts, creating small vesicles filled with a serous, transparent liquid, a mixture of cellular fragments and blood. If the itch is not cured, these vesicles enlarge, and fill with pus, thereby becoming pustules. Patients treated for the itch in Parisian hospitals often suffered from an advanced stage of the disease, which explains why the itch was also called psoris pustulosa.2 For his thesis, Gales removed the sarcoptes from the early vesicles.3 He observed them under the microscope and compared them with early descriptions of the itch-insects. To discriminate between the sarcoptes and the flour-mite (which is very similar), Gales reproduced the itch by "inoculating" himself with the sarcoptes, thus demonstrating that the itch was caused by the sarcoptes and not by the flour-mite. In the years that followed, however, it proved impossible to find the sarcoptes on itchinfected persons. Moreover, the figures in Gales' thesis, which depicted the flour-mite and