TOO 



2. The Mid-gut. This extends from the level 

 of the first pair of legs to the posterior border of the 

 sixth abdominal segment. 



(i) An anterior narrow portion resembling an 

 oesophagus. 



(ii) A posterior dilated portion at the level of 

 the sixth (and fifth) abdominal segments in which, 

 if the last meal of blood is not quite digested, a black 

 mass will be seen. If any blood remains in this portion, 

 i.e., c the stomach,' discard the specimen for one 

 kept longer without food, as it is otherwise very 

 difficult to see zygotes. 



(iii) At the commencement of the mid-gut a 

 ring-like, thickened portion (the proventriculus). It 

 acts as a valve between the oesophagus and mid-gut. 



3. Malpigbian tubules. Passing between the 

 mid-gut and the separated segments, note five 

 brilliantly white threads the malpighian tubules. 



4. Hind-gut. Between the malpighian tubules 

 the transparent intestine which may exhibit active 

 peristalsis. 



5. Oesopbageal diverticula. Attached to the 

 proventriculus an exceedingly delicate membrane, the 

 dilated oesophagus and three diverticula of the same, 

 which usually contain gas bubbles. Schaudinn has 

 shewn by adding baryta water to these bubbles that 

 they are really carbonic acid gas. Further, also, the 

 bacteria in these diverticula produce enzymes which 

 are the cause of the * irritation ' of the bite, as may 

 be shown by rubbing a diverticulum into a scratch on 

 the skin. The salivary secretion as has been generally 

 supposed has not this property. 



The ventral "diverticulum extends as far back 

 as the fifth abdominal segment. 



