OF THE NERVOUS SYSTEM IN GENERAL. 465 



name of medulla oblongata. In this last part, besides the an- 

 terior and posterior fascicles, there is on each side a lateral 

 fascicle. 



The lateral fascicles, increased by the corpora olivaria, are 

 prolonged, for the most part, into the tubercula quadrigemina, 

 and terminate there. The posterior fascicles, after being en- 

 larged in the corpus rhomboideus, expand in the cerebellum 

 and form it; extending beyond, they unite on the one hand at 

 the median line, under the medulla oblongata, where they form 

 the annular protuberance or pons varolii, and on the other hand 

 they unite with the tubercula quadrigemina. The anterior fasci- 

 cles, after mutually crossing each other, united with a part of 

 the lateral, enlarged in the optic thalami, and the corpora 

 striata, expand in a radiated manner to form the hemispheres 

 of the brain, and unite at the median line in the corpus cal- 

 losum. 



The nervous cords or the nerves, to the number of forty 

 pairs and upwards, join the medulla by one extremity; they 

 present a certain number of plexuses where they communicate 

 with each other; numerous ganglions are met with in their 

 course; [tine cords terminate by another extremity in the two 

 teguments, the organs of sense, the muscles, and in the coats 

 of the vessels, especially of the arteries. 



743. The form of the nervous system is, in general, sym- 

 metrical; the symmetry is especially marked in the central 

 parts, still more so in the spinal marrow than in the encepha- 

 lon, where the surface of the lobes of the brain, and cerebellum 

 always presents irregularities. The nerves which are derived 

 immediately from the spinal marrow, are all symmetrical, ex- 

 cept the pneumo-gastric, which is distributed to asymmetrical 

 organs: all, however, in their ultimate divisions, cease to be as 

 rigorously symmetrical as in their trunks. The ganglions and 

 the nerves, which belong to the asymmetrical organs of vege- 

 tative functions, participate in their central parts,but especially 

 in their divisions and peripherical extremities, in the irregu- 

 larity of these organs. 



744. The situation of the nervous system is interior and 

 central with respeet to its masses, and the nervous cords also 



