86 INTERNAL ORGANS. 



large globular lobes, which constitute the brain ; 

 in front of these are one or two other exceeding- 

 ly minute disks, similarly connected, called the 

 frontal ganglia. From either side of the brain 

 three principal nervous cords are emitted, one to 

 the ocelli, one to the antennae, and one to the base 

 of the tendinous cord which connects the princi- 

 pal muscles of the head with the mandibles ; the 

 one passing to the ocelli is the largest, tapers 

 until it approaches them, and then expands over 

 a broad area inclosing them all. 



Theoretically there is one ganglion to each seg- 

 ment of the body ; but when we reach the seventh 

 abdominal segment there are two, one close behind 

 the other, and in the succeeding segments none 

 at all ; the hinder and slightly larger one in fact- 

 represents the combined ganglia of the posterior 

 segments, and from it the nervous threads pass to 

 the very extremity of the body. At the sides of 

 all the ganglia, and from the nervous cord just in 

 advance of each ganglion, lateral threads are emit- 

 ted and pass outward toward the walls of the 

 body, branching in every direction, covering each 

 organ and muscle with filaments of nervous tis- 

 sue ; there are two of these principal branching 

 threads on either side of each ganglion, the an- 

 terior generally feeding the upper and the pos- 

 terior the lower half of the body. 



The only organs of special secretion in cater- 



