This book is the amplification of a paper, the subject of which was, "A Plea for Circumcision; or, the Dangers that Arise from the Prepuce," which was read at the meeting of the Southern California Medical Society, at Pasadena, in December, 1889. The material gathered for that paper was more than could be used in the ordinary limits of a society paper; it was gathered and ready for use, and this suggested its arrangement into book form. The subject of the paper was itself suggested by a long and personal observation of the changes made in man by circumcision. From the individual observation of cases, it was but natural to wish to enlarge the scope of our observation and comparison; this naturally led to a study of the physical characteristics of the only race that could practically be used for the purpose. This race is the Jewish race.