NATURAL THEOLOGY. 185 



juice of the sheep and the ox speedily dissolved 

 vegetables, but made no impression upon beef, 

 mutton, and other animal bodies. Mr. Hunter dis- 

 covered a property of this fluid, of a most curious 

 kind — viz., that in the stomachs of animals which 

 feed upon flesh, irresistibly as this fluid acts upon 

 animal substances, it is only upon the ^Zea^Z substance 

 that it operates at all. The living fibre suffers no 

 injury from lying in contact with it. Worms and 

 insects are found alive in the stomachs of such ani- 

 mals. The coats of the human stomach, in a healthy 

 state, are insensible to its presence ; yet in cases of 

 sudden death, (wherein the gastric juice, not hav- 

 ing been weakened by disease, retains its activity,) 

 it has been known to eat a hole through the bowel 

 which contains it.* How nice is this discrimina- 

 tion of action, yet how necessary! 



But to return to our hydraulics. 



IV. The gall-bladder is a very remarkable con- 

 trivance. It is the reservoir of a canal. It does 

 not form the channel itself — i, c, the direct com- 

 munication between the liver atid the intestine, 

 which is by another passage — viz., the ductus he- 

 paticus, continued under the name of the ductus 

 communis ; but it lies adjacent to this channel, join- 

 ing it by a duct of its own, the ductus cysticus : 

 by which structure it is enabled, as occasion may 

 require, to add its contents to and increase the flow 

 of bile into the the duodenum. And the position 



* Phil. Trans, vol. Ixii. p. 447. 

 *16 



