OF INSECTS. 
147 
selves into tlie canal in front of the chylifying por- 
tion of it. In support of the older and more gene- 
rally received opinion, that the function of these 
vessels is analogous to that of the liver, it is alleged, 
that by their insertion in the intestinal canal they 
correspond to the gall-secreting organs of other 
animals; that there is often a bladder-shaped dis- 
tention where they join the canal, forming a kind of 
gall-bladder; that the vena porta which conducts 
the blood to the liver takes its rise from the fatty 
matter within the ventral cavity, as is the case with 
the vessels in question ; and that the liver of closely 
allied animals (such as crabs, and annelides) consists 
likewise of such vascular appendages to the intes- 
tine.* Amid these conflicting sentiments, a mixed 
opinion best harmonises with the facts, and such 
has accordingly been adopted by Meckel, Tiedemann, 
J. Muller, and Burmeistcr ; viz. that the vessels in 
question have a double function, sometimes secret- 
ing bile, at other times urine. Whether they secrete 
the one or the other probably depends on the point 
of their opening into the canal being within the 
region of the chylific ventricle, or posterior to it. 
In these circumstances, the name suggested hv M. 
Audouin might be advantageously substituted for 
the present, for the most accurate knowledge we 
now possess of the functions of these vessels thus 
proves them to be urino-biliary . 
The changes which the alimentary substances 
undergo in the part of the canal behind the insertion 
of the vessels just spoken of, depends in some 
* Burmeister’s Manual, p. 371. 
