• In the nuclei of most cells from females there is found a distinct mass of chromatin that corresponds to the sex chromosome. It is genetically determined, has been observed in cells from every type of female human tissue studied, and is very seldom found in the nuclei in males. These facts were verified in a study of 125 normal people cf various ages by obtaining scrapings from the inner surface of the cheek with the edge of a tongue depressor. The scrapings, fixed and stained for microscopic examination, made it possible to tell the sex of the donor correctly in every normal case.
The test was also applied to three female pseudohermaphrodites, one male pseudohermaphrodite, and one eunuchoid female with gonadal dysgenesis. In these five instances the genetic sex agreed with the gonadal sex. The test yields valuable information, and for this purpose the Papanicolaou technique proved very useful, although the Papanicolaou stain was less satisfactory than cresyl violet.