Studies on the Construction of Medullary Vessels in the Flat-Bones of Human Embryos Conclusions for Reports Ⅰ,Ⅱ & Ⅲ

By studying developmental coursers of the construction of medullary vessels in scapula and pelvis of 60 human embryos covering the periods from the first terminal gravid months, the author obtained the following results. 1) In the pelvic bones, the ossification of its parts such as ilium, ischium and pubis undergoes individually and separately. As for the formation of the primary bone marrow, it commences in the latter half of the third embryonal month (twelfth gravid week) in the cases of scapula and ilium; while it begins in the fouth embryonal month in ischium and in the case of pubis in the period between the first and the middle of the fifth gravid month. 2) When more than two nutrition arteries are entering, these are anastomosed and commucicated with each other with the aid of their trunks which in turn form meshes of numerous branches and are distributed towards the periphery. 3) The venous system in the early embryonal stages can not be distinguished into main trunks and capillaries and the diameter of vascular spaces is much larger than that of arteries in the same stages, presenting a picture of intra-tissue spaces. However, in the later developmental stages they can be distinguishable into main trunks and capillaries, and they are generally distributed along with arteries. 4) In the later stages of embryos no significant changes can be observed in the mode of the distribution of medullary vessels. 5) Quite many nutirtion canals can be discerned but in general there are a few nutrition canals, though the number differs somewhat according to individual case. Whenever nutrition canals exist, they are usually seen located in a fixed location. 6) Cartilaignous canals begin to enter in the beginning of the fourth gravid month, and with the progress of development they send out numerous branches; and in the later stages a part of these canals become communicated with medullary vessels.