INTBODUCTIOK 



11 



insects. "We will only speak of some of the appendages of this 

 apparatus. 



The salivary glands pour into the digestive tube a liquid, gene- 

 rally colourless, which, from the place where it is secreted, and its 

 alkaline nature, corresponds to the saliva in vertebrate animals. It 

 is this liquid which comes in the form of drops from the tongue of 

 sucking insects. 



These vessels are always two in number. Their form is as 

 variable as complicated. The most simple is that of a closed 

 flexible tube, generally rolled into a ball, 

 and opening on the sides of the oeso- 

 phagus. 



At the posterior extremity of the 

 chylific ventricle are inserted a vari- 

 able number of capillary tubes, usually 

 elongated and flexible, and terminating 

 in culs-de-sac. Their colour, which de- 

 pends on the liquid which they contain, 

 is sometimes white, but more frequently 

 brown, blackish, or green. They appear 

 to be composed of a very slight and deli- 

 cate membrane, as they are very easily 

 torn, and nothing is more difficult than 

 to unroll and to disengage them from 

 the fatty or other tissues by which they 

 are enveloped. 



The function of these vessels is un- 

 certain. Cuvier and Leon Dufour sup- 

 posed them to be analogous to the liver, 

 and on that account they have been called 

 biliary vessels ; but as this opinion is not 

 generally held, it has been agreed to call 

 them the Malpighian vessels, after the 

 name of their discoverer. 



According to M. Lacordaire, their func- 

 tions vary with their position. When 

 they enter the chylific ventricle, they furnish only bile ; bile and 

 a urinary liquid when they enter the posterior part of the ventricle 



Malpighh 



