_ INSECTS. - 257 
physiological, and would never have been entertained but for the 
attempt to reconcile two conflicting views, and which ought always 
to be distrusted when it interferes with more extended enquiry. 
But if we suppose an organ answering to the liver to be alto- 
gether wanting in insects, then it must be proved that the separa- 
tion of bile is more important in the animal economy than the 
excretion of urea, before an argument can be borrowed therefrom 
against the function ascribed to the Malpighian vessels. We do 
not forget that by respiration and the elaboration of bile the 
quantity of carbon in the living body is diminished, and that from 
the large development of the respiratory organs in insects the 
excretory office of the liver is in a great measure dropped}. 
Nevertheless it is still highly probable that parts, whose function 
agrees with that of a liver, are not altogether absent in Insects. 
In the first place we might here refer to the great quantity of 
fat—the adipose body—situated between the skin and the intes- 
tine, which invests every organ and is of very great extent, more 
especially in larvee whose respiration is less perfect; the carbon 
and hydrogen which in other instances is combined with oxygen to 
quit the body by respiration, here forms that provision of com- 
bustible matter so necessary in the animal economy for the support 
of respiration, especially in the case of Insects, which as Nymphs 
take scarcely any food. Since then this production of fat exerts 
the same influence on the composition of the fluids as the separa- 
tion. of bile, it is not to be considered as a proceeding entirely 
arbitrary if some recognise in the adipose body an analogon of 
the liver?. The adipose body consists of a multitude of minute 
sacs or vesicles bound together by air-tubes which spread them- 
selves as a fine network on their surface. In the second place, ccecal 
appendages are seen below the muscular stomach in the Orthoptere 
(eight in Mantis, six in Gryllus, two in Acheta) which involuntarily 
call to mind the appendices pyloric of osseous fishes: they pro- 
bably secrete a fluid that performs the office of the bile in diges- 
tion’, In other insects, finally, as in the Caradict among the 
1 BuRMEISTER Handb. der Entomol. i. p. 403. 
2 OKEN Lehrb. der Naturphilosophie, 111. 1811, 8. 270 (3tte Auflage, s. 425). 
* That these blind appendages arise from an immediate extension (protrusion) of the 
intestinal canal is no proof, as Léon Durovr supposes, that they cannot be secretory 
YOLST 17 
