24 ELEMENTARY ZOOLOGY 



a long straight tube, the large intestine, which opens to 

 the exterior through the anus. 



TECHNICAL NOTE. Remove the alimentary canal, detaching it 

 from the anal end first, and working forward. 



Cut the stomach open. Note an anterior portion, the 

 cardiac cJiamber, and a smaller posterior portion, the 

 pyloric chamber. Examine its inner surface. What do 

 you find here ? This structure is called the gastric mill. 

 Food, which for the most part consists of any dead 

 organic matter, is chewed by the ' ' stomach-teeth ' ' into 

 fine bits, and is then passed into the pyloric chamber. It 

 is here that the digestive glands empty their secretion into 

 the food. These glands have the same office as have the 

 liver and pancreas combined in the toad, and so they are 

 often called the hepato-pancreas. When the stomach has 

 been removed there will be noted in the anterior portion 

 of the body paired, flattened bodies, already mentioned, 

 which connect with openings at the base of each of the 

 antennae by means of wide thin-walled sacs, the ureters. 

 These organs are the kidneys, or green glands. Their 

 office is similar to that of the kidneys in the toad, namely, 

 the elimination of waste from the body. 



TECHNICAL NOTE. Carefully remove all of the alimentary canal, 

 digestive glands, and reproductive organs. This process will expose 

 the floor of the cephalothorax. Now cut away from either side the 

 horny floor or bridge at the bottom of the cephalothorax. If the 

 specimen has not already been immersed, place it in clear water for 

 further dissection. 



The foregoing dissection will expose the central nervous 

 system. It extends as a series of paired ganglia con- 

 nected by a double nerve-cord along the ventral median 

 line from the oesophagus to the last segment of the 

 abdomen. From what points do the lateral nerves arise ? 

 Anteriorly the double nerve-cord divides, the two parts 



