




































12 THE INSECT WORLD. 
aad 

and the intestine, and urine alone when they are placed near the 
posterior extremity of the alimentary canal. 
Fig. 11 represents part of the preceding figure more highly 
magnified, showing the manner in which these tubes enter the 
chylific ventricle. 
In our rapid description of the digestive apparatus of insects, it 
only remains for us to mention certain purifying organs which 
secrete those fluids, generally 
blackish, caustic, or of peculiar 
smell, which some insects emit 
when they are irritated, and which 
cause a smarting when they get 
into one’s eyes. 
Less widely diffused than the 
salivary organs, they are often of 
a very complicated structure. In 
Fig. 12 is represented the secre- 
tory apparatus of the Carabus 
auratus, which will serve for an 
example : a represents the secre- 
tory sacs aggregated together like 
a bunch of grapes, B the canal, c 
the pouch which receives the secre- 
tion, p the excretory duct. 
Tiito Cites tctene aeparaci or Oarabrs Sometimes the secretion is 
OR iy a liquid, and has a foetid or ammo- 
niacal odour; sometimes, as in the Bombadier beetle (Brachinus 
crepitans), it is gaseous, and is emitted with an explosion in the 
form of a whitish vapour, having a strong pungent odour ana- 
logous to that of azotic or nitric acid, and the same properties. 
It reddens litmus paper, and burns and reddens the skin, which 
after a time becomes brown, and continues so for a considerable 

time. 
About the middle of the seventeenth century Malpighi at 
Bologna, and Swamerdam at Utrecht, each discovered in different 
insects a pulsatory organ occupying the median line of the back, 
which appeared to them to be a heart. Nevertheless, Cuvier, 
haying declared some time afterwards that there was no circula- 


