Food-Canal 



crosswise at right angles, a middle epithelial layer 

 of large rounded or oval flattened cells, and an inner 

 layer of chitin (continuous with the outer skin) 

 whence hairs project into the cavity of the organ. 

 Gizzard. — I3ehind the crop comes the gizzard, 

 which is small and bluntly conical, its base being 

 attached to the crop. Its walls are exceedingly 

 thick, consisting largely of muscles whose fibres are 

 arranged circularly. The inner lining is chitinous 

 and is deeply folded so as to form six large teeth, 

 which project far into the cavity of the gizzard, their 

 points nearly meeting in the centre (fig. 44). Behind 



Fig. 4^. — Cross section through part of Cockroach's gizzard, showing one tooth 

 and two intermediate spaces. Cc. Chitinous Hning ; C. layer of chitin- 

 forming cells ; am. muscles ; /. peritoneal layer. Magnified 75 times. 

 From Miall & Denny. 



the teeth the folds of the chitinous lining form ridges 

 beset with numerous hairs. The gizzard ends behind 

 in a narrow neck which projects into the cavity of the 

 stomach. 



Stomach. — The stomach is a simple tube whose 

 walls consist of an outer, thin, muscular layer, and 

 an inner layer of elongate epithelial cells, which are 

 often clustered together so as to form ridges (fig. 46). 

 From the front end of the stomach open eight short 

 blind tubes {enseal tubes) whose walls show similar 

 structure. 



