— 32 — 



' On the meson just entad of the ventral wall of the body, 

 there are two white cords, extending nearly the whole length 

 of the body. At intervals, which approximate the segments 

 in length, these cords are united ; at the points of union they 

 are greatly enlarged ; from these enlargements there arise 

 numerous, small, white cords, which extend in various direc- 

 tions. The two longitudinal cords, the enlargements upon 

 them, and the numerous cords branching from these enlarge- 

 ments constitute the nervous system ; the cords are nerves 

 and the enlargements are ganglia. The nervous system will 

 be studied later in a specimen which has been opened on the 

 dorsal side. 



Cut away from the ganglia the nerves that extend to one 

 side ; do this with the scissors, first placing one blade under 

 the nerves and lifting them away from the other viscera. 



Take a strip of sheet-cork a little longer than the insect 

 and twice as wide, and pin it to the beeswax lining of the 

 dissecting dish, and cover it deeply with water. Place the 

 specimen' on the cork and fasten with a pin at each end. 

 Turn laterad each half of the ventral wall and pin it down 

 to the cork, using ribbon-pins. 



NOTE. — At the close of the day's work on this subject the student 

 should remove the strip of cork from the dissecting dish and place it 

 with the specimen still spread^ut upon it in a wide-mouthed bottle of 

 chloral hydrate solution. Bj^Poing this the work can be resumed 

 without the necessity of making a new dissection. 



Ramifying through all parts of the body are numerous 

 trachea ; the larger tracheae are of a dusky color ; but many 

 of the smaller ones contain air, which renders them silvery 

 white. On -each side of the body, extending the entire 

 length of the thorax, are two very large tracheae ; from each 

 side of each abdominal segment except the last there arises 

 a large trachea, which divides and subdivides into numerous 

 branches. Cut a short piece from one of the large abdominal 

 tracheae, examine it with a compound microscope, and note 



