When Jirásek was appointed chief of the Embryological and Histochemical Laboratory at the Institute for the Care of Mother and Child In Prague in 1960 he began a systematic study of legally aborted human embryos. His monograph is a report of his examinations which extended to over 300 embryos whose gonads and genital systems were studied by anatomical, histological, and histochemical means. The book is copiously illustrated with good black and white photographs of developing external and internal organs and of histologic and histochemical examinations of these tissues.
The first 42 pages are devoted to normal development of the genital system beginning with embryos in the presomite stage in which germ cells are discernible in the yolk sac. The emigration of the germ cells is traced to the genital ridge and the early development of the testes is described in detail with convincing illustrations. Subsequently, an account is given of