io8 



4. Between the malpighian tubules the 

 transparent intestine which may exhibit active 

 peristalsis (Fig. 30). 



5. Attached to the proventriculus an exceed- 

 ingly 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 shewn 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. 



To Prepare the Mid-Gut for Examination 



I. Cut (by pressing with the needle) across 

 the intestine and malpighian tubes just below 

 the termination of the saccular mid-gut. This 

 will separate the mid- gut from the rest of the 

 viscera. 



Remove everything from the slide but the 

 mid- gut. Remove excess of fluid, and see that 

 no ova or extraneous matters are left upon the 

 slide. Add a small drop of clean salt solution, 

 and place a thin coverglass upon the preparation. 

 The mid-gut will flatten out considerably. Re- 

 move with filter paper applied to the edge of the 

 coverglass any excess of fluid. Examine under 

 one-third inch objective and afterwards under 

 one-twelfth. 



