82 ON THE ANATOMY OP THB FLY. 



nerves are sensory, or motor, or both ; they seem to be lost amongst the 

 muscles. 



The ninth arise beneath, between the third and fourth ginglia, chiefly 

 from the third; tl>3y supply the posterior legs, and are distributed 

 similarly to the third and fifth nerves. 



The tenth pair are small cords, which arise from the fourth pair of 

 ranglia behind ; they enter the abdomen, and are apparently chiefly lost 

 amongst the cells and fibres of the sympathetic plexus. I have distinctly 

 traced a connection between the two systems at this point. 



The ventral cord is continued from the posterior extremity 

 of the thoracic nerve centre ; its fibres may be traced passing 

 backwards from the surface of the latter. It is the great 

 abdominal nerve, and gives off a pair of nerves for each segment ; 

 it terminates in numerous branches to the generative organs. 

 No ganglionic swellings exist in this nerve. 



The sympathetic or visceral system of nerves has three 

 large and a multitude of small nerve centres. 



The largest, which I shall call the great splanchnic, should 

 probably be considered as a pair of ganglia. It is situated in 

 the posterior opening of the thorax, and is covered beneath by 

 a layer of orange brown hexagonal pigment cells. It is largely 

 supplied with minute tracheal vessels, which form a loose 

 network, between the meshes of which, a vast number of nerve 

 cells and fibres lie. The great splanchnic seems to be connected 

 with all the visceral ganglia, and to send branches over the 

 surface of all the viscera. 



A pair of large ganglia are spread out upon the surface of 

 the crura, which connect the oesophagus and lateral lobes of 

 the sucking stomach, one on each side of that organ. These 

 are closely connected with the great splanchnic ganglion. 



Numerous small ganglia abound upon the viscera, and 



