It is this consideration that has induced me not to describe the nerves of the spine as it is usually done, that is, as going from such or such pairs. I describe at first in each region the plexus that the nerves form there in going out of the spine; thus, I expose before the cervical nerves, the deep cervical plexus, before the brachial the brachial plexus, and before the lumbar and sacral the plexuses of the same name. The general arrangement, the form, the relations of these plexuses being known, I pass to the description of the nerves that go from them before, behind, without, within, &c. without regard to the pairs of nerves that come through the foramina. This method has appeared to me, moreover, to be extremely convenient for students. Nothing, for example, is more complicated than the description of the cervical nerves, by referring them to the pairs that first furnished them. But understand well at first the deep plexus, arising from the anastomoses of these pairs at their exit; afterwards class the nerves, 1st. into internal, which go to the great sympathetic; 2d. into external, which are distributed upon the acromion and the triangular space, bounded in front by the sterno-mastoideus and behind by the trapezius; 3d. into anterior, which, winding upon the sterno-mastoideus, form there with the branches of the facial a kind of superficial plexus; 4th. into posterior, which go either to the occiput, or to the posterior muscles of the neck; 5th. into those that go inferiorly, as the diaphragmatic, as those that communicate with the nervous branches of the hypo-glossal, &c. &c. In this way, you will easily retain all the nervous distributions, because you will have one point to which your memory will refer them all, and not to as many centres as there are pairs. _Internal communications of the nervous cords._