Every dermatologist and surgeon knows clinically the disease described in 1874 by Sir James Paget as a "disease of the mammary areola preceding cancer of the mammary gland," and spoken of since as "Paget's disease of the nipple," "maladie de Paget du mamelon." It occurs more frequently in America and in England than in France and other European countries, but one may ask oneself whether it is not often mistaken for some other condition or passed over in silence. The condition is usually observed in women over 40, but it may occur in men, and other parts of the body than the nipple may be affected. I shall discuss these cases further on and give an explanation of them. In the nipple the condition often begins with a serous exudation, sometimes even with a slightly sanguineous secretion, before any dermic lesion is seen. This fact seems to be most important,