130 M. straus-durckheim's 



laws of relation, and even these are subject to considerable 

 exceptions. 



The food which reaches the intestinal canal retains only its 

 chemical properties, the influence of these is sometimes very 

 sensible ; but two kinds of food which influence much the oral 

 organs, may be reduced to very nearly the same state when 

 they reach the stomach. 



We may consider the Annulosa and Annelida as being 

 divided into two divisions according to the form of the ali- 

 mentary canal : the first division contains those which have 

 all the segments nearly alike in form; the second, those where 

 the segments are dissimilar. In the former, the intestinal 

 canal makes very slight, if any folds, and mostly stretches in 

 a nearly straight line from the mouth to the amis ; whilst, on 

 the contrary, in the others it makes a number of convolutions, 

 which are more or less considerable according to the nature of 

 the food; that is to say, they are numerous in the herbivorous, 

 and few in the carnivorous. This rule has, however, some 

 remarkable exceptions, the shortness of the canal being some- 

 times compensated by an increase in breadth. In both divi- 

 sions it presents more or less distinct dilatations which mark 

 out a distinction of parts, to w^hich we may give the names of 

 oesophagus, inglumes, {jabot), i^entriculus, {jabot succen- 

 iurie), ventriculus bulbosus {gesier), and the Intestine, divided 

 into duodenum, colon, coecum, and rectum, but some of these 

 are often wanting, or have their functions performed by the 

 others. 



The relation existing between the alimentary canal and the 

 external form of the body, is a consequence naturally arising 

 from the proportion which must exist between the intestines 

 and the mass of the body. Where the segments are all nearly 

 similar, as in the Annelida and Mijriajioda, the body is 

 generally very elongate, and the alimentary canal has sufficient 

 length when extending from the mouth to the anus. Where 

 the segments are dissimilar, the body is mostly short, and 

 inflated in certain parts only, so that the intestine, in order to 

 preserve a length proportioned to the bulk of the body, is of 

 necessity expanded in certain parts, and folded upon itself, that 

 it may be confined in a shorter space. From this it follows 

 that the principal expansions of the alimentary canal are found 

 in the most dilated part of the body. In the Crustacea this 



