2024. The nerves are filaments that, upon the separation of the parts of the body, have remained behind, just like the arteries are tubes individualized in the general parenchyma, throughout which the sap was previously dispersed as in the vegetable trunk. The first individualization necessarily takes place at the oral extremity. The first nerve is a ring surrounding the pharynx or gullet. Thus, if the body consists of several consecutive rings or cysts, as in the Worms, each ring will or can have its nervous ring, which inferiorly gives off nerves to the vegetative organs, and superiorly to the animal, if these be present. Such a point for giving off nerves is called a ganglion; since also every ganglion sends off nerves to join other ganglia; so both below and above a nervous cord or string will originate in the longitudinal direction. The nerves, which have been left behind in the vegetative parts, form the vegetative nervous system; those that remain in the animal parts, the animal system. a. _Vegetative Nervous System._ 2025. The vegetative nervous system is the nervous mass that has remained behind, after the greatest part of it has become converted into tegumentary formations. Now, as these tegumentary formations, being surrounded in the higher animals by flesh, were thus viscera, so may the vegetative nerves be called also _Visceral_ or _Splanchnic nerves_. 2026. These visceral nerves govern the vessels, the intestine, and lung; with the sexual parts also, yet in their case in combination with the animal nerves, because the sexual parts are at one and the same time organs of vegetative and animal life. 2027. These visceral nerves everywhere accompany the vessels, and are therefore like these distributed in a cystic manner between intestine and skin. They form a large cyst which concentrically surrounds the intestine. 2028. They do not, however, like the intestine, form any closed cyst, but only a cystimorphous net, like the vessels. 2029. The two nervous masses are in them separated from each other, like as the branchiæ have been distributed along the whole body and separated from the intestine. The gray or branchoid substance has separated itself from the white medullary substance into individual _ganglia_, or as it were into individual nervous branchiæ. The medullary substance has also retained its connexion though only in a ramular manner, and not uninterruptedly like an integument. It is called _plexus_. 2030. The ganglia and the plexuses stand in mutual opposition, like the branchiæ and intestine, like artery and vein, like blood and lymphatic vessels. The ganglia oxydize, polarize; they are the active. The plexuses suffer, digest, and are the recipient. 2031. The visceral nerves, like the viscera, act for themselves, being unconcerned for the animal systems. 2032. The visceral nerves have a vegetable sensation for themselves, a sense of touch, such as the blossom might have in the instant of the pollenization.