There have been a number of short monographs on the subject of sternal puncture of recent publication in Europe. Few, however, have presented the subject as comprehensively in such a concise manner. The author discusses the advantages of sternal puncture as compared with trephine and section technic. The detailed technic is clearly stated and methods are described for the staining of the aspirated material. There is then a detailed discussion of the morphology and embyogenesis of cells of the sternal marrow. The author discusses the disagreement as to the nomenclature of the different young forms of red cells and adopts a classification based on cell size, reaction of the protoplasm to dyes, and the nuclear structure. He brings out the point that, while under normal conditions growth is regular and occurs through given stages, many irregular changes may take place in diseases that can be classified only with great difficulty.