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mid-gut is the only portion of the alimentary canal not 

 lined with chitin, and therefore the absorption of the 

 soluble products of digestion can only take place in this 

 region. It is inconceivable that the short mid-gut, even 

 with the mid-gut caeca, can be the only region where the 

 process of absorption is carried on. The digestive gland, 

 which is merely an outgrowth from the mid-gut, is richly 

 supplied with blood, and it is an easy matter for the fluids 

 to pass from the mid-gut into the tubules and through 

 the cells into the blood stream. Thus the digestive gland 

 becomes an accessory absorptive organ of no mean 

 importance. 



Excretory function. It was observed by Cuenot and 

 MacMunn that when a Crustacean was injected with 

 certain colouring matters, the latter were discovered in 

 the ferment cells of the digestive gland as well as in the 

 cells of the recognised excretory organ. Cuenot is of the 

 opinion that the pigment contained in the excretory cells 

 is of an excretory nature, and that when the contents of 

 these cells ultimately find their way into the alimentary 

 canal, the excretory pigment becomes separated from the 

 ferments and passes down the hind-gut to the exterior. 



Function of elimination. During the process of 

 absorption, Cuenot states that the cells of the digestive 

 gland keep back many useless products which are after- 

 wards carried to the exterior together with the excretory 

 products. This is quite distinct from the excretory 

 function. 



Function of regulation. In addition to the other 

 functions it is probable that the digestive gland is capable 

 of regulating the composition of the blood, especially with 

 regard to the quantity of water contained in the blood. 



Summary. As the food enters in at the mouth 

 it will come into contact with the secretion from the 



