.44 
ANATOMY AND PHYSIOLOGY 
visable to add some further explanation relating to 
the physiological functions of its respective parts 
besides the incidental notices on this head already 
given. The food to be transmitted through its 
various chambers, if of a solid substance, undergoes 
a process of mastication bv the oral instruments ; but 
this process is not in all cases equally complete. 
Many predaceous kinds, particularly among the Cole- 
optera, masticate their food very imperfectly, merely 
dividing it into such pieces as admit of being swal- 
lowed. Further mastication is doubtless rendered 
unnecessary in their case by the presence of a 
gizzard where the trituration is afterwards per- 
fected. Raptorious species destitute of the organ just 
named, (such as Dragon-flies) thoroughly comminute 
their food before swallowing it. Solid vegetable 
matters are of course always considerably reduced in 
the mouth ; but those insects which feed on green 
leaves, particularly the caterpillars of Lepidoj)tera, 
swallow the small pieces they detach almost or en- 
tirely unchanged. In suctorial insects, as well as 
those which have been termed Lappers (the Stag- 
beetle is an example), mastication obviously becomes 
superfluous. 
But it is not the mechanical action of the trophi 
(as the oral organs are sometimes called) alone that 
the food is subjected to in the mouth ; it is here that 
it mingles with the secretions of the salivary vessels. 
These secretions consist of a whitish, frequently a 
purely hyaline fluid, said to be of an alkaline nature. 
The intermixture, to adopt Burmeister’s words, has 
