The relation between the number of hookworm ova in the stool of an individual and the actual number of hookworms harbored in the intestines is not constant. In a previous communication (1), we reported experiments in which many individuals were found negative by the routine microscopic test and yet yielded large numbers of hookworms on treatment.
One criticism of this study was that the routine microscopic examination of feces as carried out in field hookworm posts is subject to errors for which the microscopist himself is not responsible. For example, when one distributes a number of specimen tins to illiterate individuals of the same family, certain errors in collection of the stools are almost sure to occur because the patients cannot read their own names on the tins and the specimens therefore become mixed. Thus, though the microscopic examinations are carefully made, the reports of the microscopist are not correct because of a mistake in collection of the specimens.