THE COMMON COCKROACH 137 



The gizzard opens behind into a short narrow tube of 

 about the same diameter as the resophagus, and called 

 the mesenteron, or mid-gut. Where this joins the 

 gizzard, there are eight blind tubes radiating from it, 

 tubes, i.e., that are closed at their outer extremity but 

 open at the other end into the mesenteron. They 

 are called hepatic cceca, and secrete a juice which is 

 needed in digestion, and which, when food has to be 

 digested, is forced up into the crop, and there performs 

 that operation, the passage leading into the gizzard being 

 meanwhile closed, that no food may pass the junction 

 till it has been suitably modified. The gizzard would 

 seem to be not very correctly named, as it appears to 

 act more as a strainer than as a triturator. At the end 

 of the mesenteron we again meet with a circle of blind 

 tubes, but these are far more minute and far more 

 numerous than those at its commencement. They are 

 some sixty or more in number, and are arranged in six 

 sets. They are so fine that they look simply like a 

 tangle of the finest gossamer threads. Individually they 

 are very long, and twist about in all directions, and 

 amongst the other organs situated in their neighbour- 

 hood. They are called Malpigliian tubules, and though so 

 fine, are in reality tubes, closed at their outer end, but 

 opening into the intestine. They are excretory in func- 

 tion, and appear to perform the office of kidneys. Suc- 

 ceeding the mesenteron, we get the intestine, which is 

 divisible into three regions. The first is a short narrow 

 tube, called the ileum ; the second a much longer and 

 broader one, the colon, with loose baggy walls, and con- 

 tracted towards its hinder extremity ; and the third a 

 pear-shaped body, with its internal walls set into six 

 prominent ridges or folds ; this is called the rectum. 



The whole alimentary canal, from the commencement 



