OF DIGESTION. 373 



digestion, it may be asked what is the function of the biliary vessels ? 

 Are they urinary organs or kidneys ? Certainly not; for where shall we 

 find, throughout the whole animal kingdom, an instance of the ureter 

 emptying itself into the middle of the intestinal canal? And is not this the 

 case with the biliary vessels in many, indeed the majority, of instances ? 

 The uric acid which chemists have found therein proves nothing, for 

 many parts of the body of insects contain this acid, as Rudolph! * also 

 correctly observes, it islikewise found in many other fluids besides urine f. 

 Lastly, the resemblance of the biliary vessels to the urinary organs is 

 too trifling, and the latter are always in closer connexion with the 

 sexual organs than with the intestinal canal ; besides, in some insects, 

 namely, in the Carabodea, Dytici, and Slaphylini, distinct urinary 

 organs have been found ( J13), the secretion of which indeed has not 

 yet been proved by analysis to be urine, but which, both by their resem- 

 blance in form, and partly by their situation, have proved themselves 

 urinary organs. Joh. Muller J, who has most strongly supported the 

 consideration of the biliary vessels as kidneys, will not admit of these 

 organs being considered as secreting urine, but explains them to be 

 peculiar glands which secrete a sharp liquid, and compares them with 

 the poison glands of the Hymenoptera ; but even if we admit of this 

 analogy we must yet oppose his assertion that the insects which are 

 provided with these organs secreting a sharp liquid, for it is supported by 

 no other observation than at most the explosion of the Brachini. As 

 this exploding secretion is gaseous, it cannot necessarily be secreted by 

 these organs, but may be merely be the air contained within the broad 

 colon. Whereas the Dytici, upon being seized^ as I have frequently 

 observed, eject their hyaline livid urine, which has a peculiar pungent 

 smell, very like feverish or corrupt human urine, but which never 

 acts acutely or poisonously, and inflammatory. We may here justly 

 ask why these few insects only have urinary organs, and the majority 

 want them, which is absolutely a difficult problem to solve ; but 

 in some others, for example, Bombylius, Leptis, the same organs are 

 again found, and in Gryllus migratorius, Fab., I observed a single 

 serpentine vessel, which originated from a small kidney-shaped organ, 

 and which opened at an analogous spot near the anus. It is therefore 



* Physiologic, vol. ii. part ii. p. 145, note 1. 



f Guiel. Handb. d. Theor. Chcmie, vol. ii. part ii. i>. 1473 



J De Gland, secern, struct, pen., p. <J!>. 



