40 



HIGH SCHOOL ZOOLOGY. 



or peritoneal lining l.y means of a double fold thereof, known 

 as the mesentery. If, as in most animals the intestinal canal 

 be longer than the coelom, it is evident that the m&sentery must 

 be longer along the line of its intestinal attachment tli.tn ;tlong 

 that where it is continuous with the ccelomic lining. If then 

 the intestine be thrown into coils, so as to be accommodated with- 

 in the ctelom, the mesentery must likewise })e coinplicated in its 

 form. Between the two folds of the mesentery the blood-vessels 

 and nerves which pass to and from the intestine are accom- 

 modated. Immediately within the serous coat of the intestine 

 is the muscular coat, in which two lay era are recognized, an 

 outer of longitudinal, and an inner of circular fibres, Thase 

 fibres are of the involuntary order, except in the oesophagus 

 where the inner circular coat is wanting and the lonjritudinal 

 fibres are surrounded by voluntary or striped fibres. Within 

 the muscular coat we find more or less submucous tissue, 



answering to the subQutaneous tissue 

 of the skin, and finally the mucous 

 coat which forms the lining of the 

 inte^stine, and in which, as in the 

 skin, we recognize two layei^s, a con- 

 nective-tissue and an epithelial. The 

 latter is the characteristic tissue of 

 the intestine, and forms the bulk of 

 those glands which contribute the 

 various digestive juic&s. (Fig. IG). 



51. Although there is no marked 

 boundaiy between the stomach and 

 cesophagus, the former is decidedfy 

 "wider, and much more abundantly 

 Fig. ic— Lon^tudinal Section of supplied with blood. This is neces- 



Intestinal Wall of Catfish. /• .i t i r» ,i 



.sary tor the proper discharge oi the 



Ep, epithelium; ra, mucosa; „ . r \ • i i 



cm, drouiar, im, longitudinal mus- function of the gastnc gland.s, tubes 



cle& 



