I conducted field research in Mexican folk medical beliefs and practices under the auspices of the Dept. of Anthropology, University of California, Berkeley during the summers of 1963 and 1964 in the village of Erongarícuaro, Michoacán, on the shores of Lake Pátzcuaro in Central Mexico. Funding was generously provided by the Research Committee of U.C. Berkeley, the National Science Foundation, and the National Institutes of Health. The article in its present form was published in 1966 in Ethnology,  Vol. 5, No. 3, pp. 251-263.