In this Atlas I want to share with my fellow clinicians the fascina tion I experienced while discovering the marvels of embryonic development. Why haven't these marvels excited me before? I believe that the use of schemata and drawings or photographs of animal embryos, commonly used in textbooks of embryology, simply did not appeal to me as a clinician. Only actual photo graphs of human embryos can establish the bond necessary for interaction. Just imagine the excitement when you find out how many struc tures you can recognize in a 5-week-old embryo, barely measuring 1 cm in length. But our fascination does not stop here. The pro gression of changes taking place during the next 3 weeks is so rapid that at the time when the embryo measures 3 cm, all structures familiar to us are not only easily recognizable, but also already in their anatomical position. How can we hide our amazement when we realize that such a state of perfection is present in an embryo a bit longer than the distal phalanx of our little finger? At 8 weeks the embryonic period ends and the fetal one starts. Although the shape and the relative size of bones, joints, muscles, nerves, and vessels will undergo changes, the basic elements are all in place. This implies that major malformations must develop during the embryonic period."

External fixation is now being used widely to maintain fractures, osteo tomies, and arthrodeses in a desired position during consolidation. Whereas external fixation has been readily accepted in European countries, its use has weathered a rather stormy course in North America, especially in the treatment of fractures. Only recently has external fixation found its rightful place on this continent as well. Many different models are on the market today, and the practitioner is faced with a difficult decision in selecting a model. Should he buy a system where the fracture has to be reduced first, or should he work with a device permitting a reduction after insertion of the pins? To enable surgeons to study the different systems, to discuss their advantages and disadvantages, and to permit them to put their hands on these devices and inspect them personally, the Division of Orthopedic Surgery, University of Ottawa organized an applied basic science course in May 1981, External Fixation of Fractures. During this course, all major systems were pre sented to the participants. As happened during the course "Internal Fixation of Fractures" held two years ago, the rigidity of internal fixation was frequently and intensively debated. Whereas the rigidity of internal fixation cannot be altered during the course of healing, the rigidity of external fixation can be changed. In fact, with progression of union, rods of increasing elasticity can be used."

"Physiaians have aZways known, though often they are reZuatant to adrrrit it, that the quaZity of their daiZy praatiae depends on the resuZts of researah * . . Irvine H. Page * The 1985 App1ied Basic Science Course distinguished itse1f for three impor- tant reasons. First, it showed c1ear1y the extent to which biotechnology and biomechanics have become an integral part of orthopedics. Second, it emphasized the increasingly important role the orthopedist will have to play in the treatment of the aging population. Projected Canadian statistics estimate that the population aged 65 years and older will in- crease from the current 9. 7% to 13% by the year 2000. Based on the current total population of almost 25 million, the number of hip fractures caused by age-related bone 1055 will almost double and will reach approximately 28,000 per year in Canada. Extrapolation of these figures according to populations in other countries is easy. The costs in expenditures and human suffering are inestimable. This is an area where orthopedic research will have to redouble its efforts in the hope of finding better preventive measures. Furthermore , knowledge of the pathogenetic mechanisms of bone 1055 becomes increasingly important in osteoporosis associated with weightlessness. The third impressive insight we derived from the presentations at this sym- posium was the revelations of the latest imaging techniques and monitoring devices. Nuclear medicine, computer assisted tomography, and nuclear- magnetic resonance are being applied to bone disease.