106 
CHAPTER XVII. 
DIGESTIVE APPARATUS. 
Object of Digestion — CEsophagus — Honey Sac — Sto77iach Aloiith 
— Its Use a7id Volu7ita7y Actio7i — Muscles — P7'olo7tgatio7i — 
St7nictu7'e of Chyle Sto77iach —Sec7'etmg Cells — Gastric Juice 
— Chy77ie — S77iall a7td La7ge Htestmes — Malpighia7t Tubes 
— Gastric Teeth — Chyle — Rectal Glands. 
The object of digestion is to separate the nutrient 
part of food from the non-nutrient, and to convert 
the former into a liquid fit to mingle with the 
blood, and thus to nourish the body of the insect. 
This elaboration takes place in a cavity communi- 
cating with the exterior, into which the food is re- 
ceived, and from which the non-nutrient portions are 
expelled. 
Many writers have described the digestive system, 
amongst whom are Swammerdam (158), Treviranus 
( 163, 164), Brandt and Ratzeburg, Dufour (32), 
Reaumur (139), and others. 
It is divided into four principal parts. ' The oeso- 
phagus.^ or gullet (frontispiece, /), which passes 
through the thorax, expands into an enlargement 
called the honey sac^ or hotiey stomach (g) connected 
by a short neck to the chyle siomach (/), the small 
intestine, or ileum (k)^ and the large intestine, called 
rectum., or colon. 
The food taken by the mouth enters the oesopha- 
gus, which continues through the thorax as a narrow 
tube, and expands, after it has reached the abdomen. 
