58 



The Larva of Cliiyononms 



Musculiii' 

 coat, of 

 stomach. 



does not at once come into contact with, the food ; it 

 is separated therefrom by the peritrophic membrane, 

 which, extends throughout the stomach. Between the 

 epithelium and the membrane is a narrow space, which 

 is occupied by a granular iiuid, probably derived 

 from the protrusions ; it contains also granules of 

 larger size, which we suppose to come from the food. 

 It is not necessary to suppose with Gehuchten that 

 the secreted fluid diffuses through the peritroj^hic 



membrane ; the granules 

 just noted indicate that 

 another communication 

 exists. We think it prob- 

 able that fluid squeezed out 

 from the food in the oeso- 

 phagus and oesophageal 

 valve passes down the 

 cylindrical tube formed by 

 the peritrophic membrane, 

 and that it is regurgitated 

 into the outer space by the contractions of the mus- 

 cular chamber in which the small intestine begins (see 

 p. 66). 



The muscular coat of the stomach consists of two layers, 

 an internal layer of annular fibres with frequent anasto- 

 moses, and an external longitudinal layer (fig. 44). A 

 connective-tissue membrane invests both the inside and 

 outside of the muscular layer, and is sometimes seen 

 detached from the underlying epithelium in the meshes 

 between the muscles \ 

 Peritrophic Tlic proper chitinous lining of the stomodaeum usually 



membrane . . "^ 



of stomach, ccases in insects at the lower end of the oesophagus. 

 Nevertheless it is not uncommon ^ to find that the stomach 



' e. g. wlien the epithelium is macerated in weak alkali. 



' Examples have been discovered in all the chief orders of insects (see 



Fig. 44. — Muscular coat of stomach 

 of larva, after immersion in i per cent. 

 sodic carbonate, showing longitudinal 

 and transverse fibres^ The basement- 

 membrane bulges out between the 

 muscles on the sides. 



