ti T : N E R A L A X A T M Y .- 



brain, which is therefore the nervous centre. Me attempted 

 to establish a distinction between the nerves of feeling and 

 those of motion, and first described and named the nervous 

 ganglia. He had also made considerable progress in the know- 

 ledge of the nerves in particular. The anatomists of the Ita- 

 lian school having found neurology much in the state to which 

 Galen had brought it, greatly improved its condition. G. 

 Bartholin reproduced the opinion of Praxagoras and some 

 others of the ancients, that the spinal marrow is the centre of 

 the nervous system, and that the brain is only a continuation 

 of it. From this period, the anatomy of the nervous system, 

 whether in animals, or in the human species, has been contin- 

 ually enriched by new facts. 



737. The most simple animals have no distinct nervous 

 system (28.) 



The first in which it begins to make its appearance are the 

 radiated animals, and in particular the asteriaB or sea-stars, in 

 which it consists of soft threads and small enlargements dis- 

 posed around the mouth, both white and destitute of cincritious 

 matter. 



In all the other invertebrate animals, the nervous system 

 consists of two more or less approximated cords, brought to- 

 gether into a greater or less number of knots or ganglia, im- 

 properly called spinal marrow in the articulata, always united 

 around the oesophagus or above the mouth by a nervous ring 

 at least, and often by a ganglion, of which the volume is pro- 

 portionate to the greater or less degree of complexity of the 

 head, and which, in the mollusca, receives the name of brain. 



In all these animals, the two teguments and their muscles, 

 the organs of the vegetative functions and those of the animal 

 functions, receive similar nerves. . 



However, there already occurs in the nervous ganglion of 

 the cephalopoda, (50) an evident indication of a nervous cen- 

 tre peculiar to the organs of sensation and motion. 



738. In the vertebrate animals,* the nervous system con- 



* See M. Tiedemann's excellent work: Anatomic und Bildungsgcschicli!< 

 des gehirns t &c. Niirnberg, 1816; translated into French by M. Jourdan: 

 Anatomic du cerveau, contenant thistoire de son dcvdoppemcnt dans lefatus, 



