316 



ZOOLOGY. 



The intestine (ileum) lies in the fifth and sixth abdominal 

 segments. 



Behind the intestine is the colon, which is smaller than 

 the intestine proper, and makes a partial twist. The colon 

 suddenly expands into the rectum, with six large rectal 

 glands on the inside, held in place by six muscular bands 

 attached anteriorly to the hinder end of the colon. The 

 rectum turns up toward its end, and the vent is situated 

 just below the supra^anal plate. 



Having described the digestive canal of the locust, we 

 may state in a summary way the functions of the difEerent 



divisions of the tract. The 

 food after being cut up by the 

 jaws is acted upon while in 

 the crop by the salivary fluid, 

 which is alkaline, and pos- 

 sesses the property, as in ver- 

 tebrates, of rapidly transform- 

 ing the starchy elements of 

 the food into soluble and as- 

 similable glucose. The diges- 

 tive action carried on in the 

 crop [ingluvies) then, in a veg- 

 etable-feeding insect like the 



Pig 377. --Trall^<v. r e, section of the loCUSt, rCSults in the COnVCr- 

 cm-p of Oryll'isclnereiiso! E\\TOfe\rmic, . » :i j. i ij_ 



muBcnlar walls ; r. horny ridge between SlOn 01 the Starcny matters 

 the largo teeth. — After Minot. • , i rm • 



into glucose or sugar. This 

 process goes on very slowly. When digestion in the crop 

 has ended, the matters submitted to an energetic pressure 

 by the walls of the crop, which make peristaltic contrac- 

 tions, filter gradually through the short, small proventricu- 

 lus, directed by the furrows and chitinous projections lining 

 it. The apparatus of teeth does not triturate the food, 

 which has been sufficiently comminuted by the jaws. This 

 is proved by the fact, says Plateau, that the parcels of food 

 are of the same form and size as those in the crop, before 

 passing through the proventriculus. The six large lateral 

 pouches (coeca) emptying into the commencement of the 

 stomach (ventriculus) are true glands, which secrete an al- 



