HISTOLOGY OF THE N Eli VOL'S SYSTEM. 



95 



2. Flhwiis Portion. This occupies the central part. It 

 consists of a close and complicated network of nerve-libres inter- 

 mingled with connective tissue. Some of these li])res communi- 

 cate with branches of the nerve-cells, as stated al«n'e; otiiers 

 run out into the lateral nerves, while still others run alunf*- the 

 connnissui'es to connect with libres from other irantrlia 



Fig. 42.— Two of the ventral ganglia (I, II) of Lumhrkns with the lateral nerves, 

 showing some of the motor nerve-cells and fibres (black), a sends fibres for- 

 wards and backwards within the nerve-cord; /», a fibre into one of tlie double 

 nerves on its own side ; c and d, fibres that cross to the nerves of the opposite side. 

 (After Retzius.) 



According to the latest researches (of Lenhossek and Retzius) most if 

 not all of the nerve-cells of the ventral cord are motor in function. Near 

 the centre of each ganglion (Fig. 42, e) in a sinirle large multipolar cell of 

 doubtful nature. All the other cells are either bipolar or unipolar, in the 

 latter case sending out a single branch which soon divides into two. In 

 every case one of the branches breaks up into fine sub-divisions within the 

 cord. The other branch in most cases passes out of the cord through one 

 of the lateral nerves to the muscles or other peripheral organs, either 



