— 33 — 



its characteristic appearance, so as to be able to distinguish 

 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 ali- 

 mentary 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 or fat. 



Make a drawing of a piece of adipose tissue showing the 

 general form of the masses. 



Examine a bit of adipose tissue with a compound micro- 

 scope, using a high power, and make a drawing showing the 

 minute structure of the tissue ; in preparing the specimen 

 care must be taken to avoid crushing the fat cells by pressure 

 on the cover-glass. 



In the farther dissection of this specimen the adipose tissue 

 may be cut away when necessary to see the parts studied. 



Form of the Alimentary Canal. — Remove the ventral 

 wall of the head so as to exnose the alimentary canal 

 throughout its entire length. ^^F 



Make a drawing of the alimentary canal and label the fol- 

 lowing parts : — 



Pharynx. — The somewhat trumpet-shaped part of the ali- 

 mentary canal immediately caudad of the mouth is the. phar- 

 ynx. 



(Esophagus. — That part of the alimentary canal which is 

 immediately caudad of the pharynx and which traverses the 

 caudal part of the head and the cephalic part of the thorax 

 is the oesophagus. It is a straight tube of nearly uniform 

 diameter except when some portion of it is distended by 

 food. 



