429 



abdomen, then gradually bending backwards passes as a long 

 tube into the rectum. The small intestine is about as wide 

 as the gizzard, but in the region of its junction with the 

 stomach it is considerably dilated. 



The rectum is a short spacious chamber. Into it pro- 

 ject, from its anterior walls, a single pair of remarkable 

 organs, the reetal glands (figs. 22, 164). Behind, the chamber 

 narrows, and opens by a short duct to the exterior. 



Two structures must be considered in connection with the 

 intestine : the salivary glands and the malpighian tubes. 



The salivary gland is in the form of a single rounded 

 clump_pf cells, lying in the postero- ventral region of the head', 

 in' the midline. It opens by a single duct into the buccal 

 cavity. The salivary duct, however, extends far past the 

 salivary glands; it travels upwards, along the posterior portion 

 of the head, and ends blindly, after making a few irregular 

 turns in the anterior portion of the thorax dorsal to the 

 intestine. This distal prolongation must evidently serve as a 

 salivary receptacle, and itself also contains some gland cells. 



The maljnghian tubes are in the form of eight slender 

 thread-like structures bending in various directions and all 

 opening into the anterior part of the small intestine, close to 

 its opening into the stomach. 



The minute structure of these parts varies considerably. 

 The buccal cavity is lined internally by ohitin which develops 

 numerous thorn-like bristles, all projecting forwards. The 

 pharynx is a great dilated portion of this buccal cavity. Its 

 walls consist of a single layer of cubical epithelial cells, larger 

 behind than in front. The pharynx, as well as all the suc- 

 ceeding portion of the foregut, is lined with a thin chitin 

 sheath (fig. 124). 



Tlie epithelium of the oesophagus consists in the liead- 

 and-''neck" region of more flattened cells; in the ventral 

 portion of the oesophagus before it enters the ''neck" there 

 is a thickening of this epithelium; and within the thickening 

 lies a prominent chitinous bar, terminating in front in the 

 region of the circumoesophageal connectives, and connected 

 behind, by two very short chitin pieces, with the rear of the 

 head. The remainder of the oesophagus is a simple fine hair- 

 like tube which traverses the thorax close above the nerve 

 cord, and enters the crop, within the abdomen. Its walls con- 

 sist of extremely minute delicate spindle-shaped cells, with 

 their long axes arranged longitudinally (fig. 158). Only with 

 the greatest difficulty can nucleus and cytoplasm be observed. 

 Internally it is lined by an extremely delicate chitin sheath. 



