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In the uteri of children, of which I have several well injected preparations, the right and left arteries appear to he as independent as those of the heart. An injection of the arteries of one side is always followed by the perfect filling of the vessels of that side, and the absence of injection in the other. However, in the vagina, and more especially in the bladder, there are large anastomoses between the right and left arteries of these organs, a circumstance which is of some importance in the development of certain pathological changes. When, in man, there are two, three, four, or even (as sometimes) five renal arteries, you may inject one, and yet none of the others will be filled, every one of these arteries having a distinct province of its own. It is the same case in other Mammalia, when their kidneys have more than one artery entering at different portions of their surface; for instance, when an injection of the horse's kidney is made, one can spare the injected matter, by selecting any small artery which enters the external surface of the organ (not in the hilus). A minute injection of a very limited portion of the cortex is thus obtained, and there is no risk of wasting the injected material by filling other parts, not required for the preparation.

An isolated injection of the middle meningeal artery makes it evident, that this artery is not only destined to be the nutritive artery of the cranium, but also, that very numerous off-sets of the diplöetic branches pass out to the external surface of the calvarium and ramify freely throughout the pericranium. When a well injected preparation of this artery is exposed to the action of weak hydrochloric acid, the destruction of the earthy matter gives to the skull (after being well dried and saturated with turpentine) such a degree of transparency, that the perforating branches of the diplöetic arteries can be distinguished with the greatest facility.

It happens very often, that the occipital artery seems to send a branch through the mastoid foramen; it is very commonly believed that this branch appertains to the dura mater, and is an accessory nutritive artery (Art. meningea externa accessoria). Now, when a series of isolated injections of the occipital artery are made, it is easy to show that, in many instances, the artery which passes into the mastoid foramen does not pass through it, and that it is, therefore, no meningeal artery. The hammer and chisel, or the help of muriatic