35 



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 speci- 

 men still spread out upon it in a wide-mouthed bottle of chloral hydrate 

 solution. By doing this the work can be resumed without the necessity of 

 making a new dissection. 



Ramifying through all parts of the, body ^re numerous 

 trachecc ; 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 abdom- 

 inal tracheae, examine it with a compound microscope, and 

 note its characteristic appearance, so as to be able to distin- 

 guish tracheae. 



In the dissection of this specimen, the student may cut 

 tracheae and nerves freely ; but great care should be used 

 not to cut other vessels unless specially directed to do so. 



In the center of the perivisceral cavity and extending the 

 whole length of the body, there is a large tube ; this is the 

 alimentary canal. 



Adipose tissue. — Surrounding the caudal half of the 

 alimentary canal and attached to the lateral and dorsal walls 

 of the abdomen and thorax, there are large, flocculent 

 masses of a white substance ; this is the adipose tissue ox fat. 



Examine a preparation of adipose tissue, with a compound 

 microscope, using a high power, and make a drawing show- 

 ing the minute structure of the tissue. 



