I would observe with regard to this, that it is necessary to distinguish accurately these communications from anastomoses, in which two nervous filaments coming in an opposite direction, are confounded and identified with each other, which is seen between those of the facial, the sub-orbitary, the mental, &c. _Nervous trunks._ After having thus communicated at their exit, the nerves separate from each other and go towards the different organs. They form at first considerable trunks, which pass through the great cellular interstices and go over a greater or less extent. The form of these trunks is sometimes flattened as in the sciatic; but it is most commonly rounded; but the form does not affect nervous action, for the nerves that are naturally round, when flattened by a tumour, perform their functions as usual. In general, whenever it does not interfere with her design, nature chooses the round form for the organs of animals. I would observe also, that this form requires a system generally diffused, and destined to fill up the spaces that necessarily exist between round organs; this system is the cellular. It would be infinitely less necessary, if the form of our organs was square, because there would be less space between them. The nervous trunks are of different length. Those of the extremities hold the first rank in this respect, because the extremities being very distant from the origin of the nerves, these trunks must of course go over a certain extent before distributing their filaments. In the trunk and the head, on the other hand, as the organs are presented immediately to the nerves that enter them, the division into branches is immediate, and the trunks are very short. The nervous trunks are sometimes accompanied by a corresponding arterial and venous trunk, as the brachial, crural trunks, &c.; at other times, as the sciatics, and those of the par vagum, they go separate. _Of the nervous branches, &c._ As the trunks advance, they furnish here and there different branches; these give out smaller ones, which send off those that are still smaller, from which arise the last divisions. All these different divisions take place at very different angles. The acute angle is the most common. It is not a real origin, but merely a separation of many cords united, that forms the branches, of one or two of these for the smaller ones, of one cord only for the still smaller, and of separate filaments for the last divisions. Thus this separation is made more or less high, in different subjects. The place where it happens is never exactly determined. According to these divisions, the filaments which compose the cords of each nerve and these cords themselves, are of different lengths; the shortest separate first, then the middling; in fine, the longest filaments of all go the whole extent of the nerve, and only terminate where it ends. The brachial and crural nerves exhibit this arrangement in a remarkable manner.