INTRODUCTION, 43 



sucked in when the animal takes it in a liquid 

 form, is swallowed by muscular motion of the hin- 

 der part of the mouth and of the throat, and 

 deposited in the upper region of the alimentary 

 canal, which usually consists of,one, and sometimes 

 of many stomachs ; there the food is penetrated by 

 juices calculated to dissolve it ; carried then into 

 the remaining part of the canal it receives an ac- 

 cession of other juices to complete its preparation 

 for being absorbed ; the coats of this canal are po- 

 rous., and thus absorb from the alimentary mass 

 such parts as are suitable for the purposes of nutri- 

 tion ; the useless residue is rejected by muscular 

 action in the form of excrement. 



The canal in which this first act of nutrition is 

 performed is a continuation of the skin, and is com- 

 posed of similar laminae . The very fibres which 

 surround it are analogous to those which are attached 

 to the internal surface of the skin, and which are 

 sometimes called the fleshy pannicle. A transu- 

 dation takes place through all the interior of this 

 canal, bearing a strong relation or sympathy with 

 the cutaneous perspiration, for it always becomes 

 more abundant when this latter secretion is dimi- 

 nished or suppressed. The absorption of the skin 

 bears likewise a strong analogy to that of the in- 

 testines. 



It is only among animals of the very lowest rank 

 that the excrement passes off by the mouth, the 

 intestines in such creatures having no other out-* 

 let, 



