Page:Natural History Review (1861).djvu/335

Rh acid, will prove that the before-mentioned arterial branch ramifies through the diplöe, reaching as far as the parietal bone. I have, for this reason, called it the ''Art. diplöetica magna'', and I consider it to be an attempt of nature to reproduce, in man, the great diplöetic artery which some years ago I discovered in the large Edentata, as a branch of the very large occipital artery, and which, in these animals, penetrates the very dense diplöe of the bones of the cranium as far as the lamina cribrosa of the ethmoid, when it escapes, and is lost, with the olfactory nerves, in the mucous membrane of the nose.

Even when, as is sometimes the case, this branch of the human occipital artery passes right through the mastoid foramen, and actually reaches the dura mater, yet a comparison of the diameter of the artery as it enters, with that of the artery as it makes its exit through the foramen, will show a very striking difference in size; the artery, as it makes its appearance at the inner side of the mastoid foramen, not having half the diameter that it possessed on its entrance into the foramen, and, even in these cases, it sends a very considerable off-shoot to the diplöe.

It is said in most works on anatomy, that this ligament serves to conduct nutritive blood-vessels to the head and neck of the femur. I venture to doubt this general assertion, on the strength of isolated injections of the arteria obturatoria, under the pectineus muscle. These injections have proved, that all the capillary vessels in the ligamentum teres are, at the point where this latter is inserted into the oval depression on the head of the femur, reflected back again into veins, forming a large number of fine capillary loops, which form a very interesting object. When a vertical section of this ligament is made, no arterial vessel can be singled out, passing from the ligament to the bony substance of the head of the femur; but if you inject the perforating artery, of which the nutritive artery of the femur is a branch, you will obtain a very satisfactory microscopical injection of the interior of the bone; and, in a vertical section of the injected femur, one may trace the vessels to the very insertion of the ligamentum teres itself, without finding a trace of even the minutest branch passing into it. Further there is no anastomosis between the vessels of the round ligament and those of the medullary cavity, which must have been the case were the blood-vessels of the former destined to nourish the frame-work of the reticulated interior of the head of the femur.