59 



ganglion is a chain of four closely connected ganglia. Lead- 

 ing back from the hindmost of these ganglia are paired, but 

 closely opposed, longitudinal nerve-cords. On these cords 

 in the sixth body-segment is another ganglion, and following 

 this are five others similar to it, each lying over the center of 

 the sternal part of a segment. These ventral ganglia, from 

 the subcesophageal back, and the connecting longitudinal 

 commissures constitute the ventral nerve chain which with the 

 brain and circumoesophageal ganglia compose the central 

 nervous system of the insect. In addition to this central sys- 

 tem there is another smaller system, the sympathetic nervous 

 system, which we shall not study in this elementary dissection. 

 Each ganglion of the ventral chain, behind the suboesophageal 

 ganglion, gives off four very conspicuous nerves; one on 

 each side arising from the middle of the ganglion going to 

 the muscles of the body-wall, and another arising from the 

 anterior end of the ganglion going to the viscera. The 1'ast 

 ganglion lying in the antepenultimate body-segment, in ad- 

 dition to the four lateral trunks, gives off from its posterior 

 part two large divergent ones running backwards to the two 

 following segments. The brain and subcesophageal ganglion 

 give off nerves to the organs of the head. 



Make a drawing of the nervous system. 



The muscular system. Along each side of the dorsal 

 and ventral median line of the body is a wide band of longi- 

 tudinal muscles. The most conspicuous fibers reach from 

 the anterior to the posterior border of each segment, but the 

 others reach from either end to the middle, while others ex- 

 tend from the middle of one segment to the middle of the 

 preceding or following segment, while still others are attached 

 to various points of the body-wall between the attachments 

 of the sets already mentioned. Finally, there is an inner- 

 most set of lateral transverse muscles in the anterior half of 

 each segment. 



