220 



THE VITAL FUNCTIONS. 



329 



general description. The only examples I 

 think it necessary to give, in this class, are those 

 of the Patella, or Limpet, and 

 of the Pleurohranchus. The in- 

 testinal tube of the Patella is 

 delineated in Fig. 329 ; where 

 M is the mouth ; t, the tongue 

 folded back ; o, the oesophagus ; 

 and s, the stomach, from which 

 the tortuous intestinal tube is 

 seen to be continued. All the 

 convolutions of this tube, as 

 well as the stomach itself, are enclosed, or rather 

 imbedded in the substance of the liver, which 

 is the largest organ of the body. 



The P leurobvanchus Peronii {C\xw .) is remark- 

 able for the number and compli- 

 cation of its organs of digestion. 

 They are seen laid open in Fig. 

 330 ; where c is the crop ; g, the 

 gizzard ; p, a plicated stomach, re- 

 sembling the third stomach of ru- 

 minant quadrupeds ; and d, a fourth 

 cavity, being that in which diges- 

 tion is completed. A canal of com- 

 munication is seen at t, leading from 

 the crop to this last cavity : b is the 

 point where the biliary duct enters. 



In the Cephalopoda, the structure of these 



