1913] Kershaw — The Alimentary Canal of Flata and other" Horn opt era 181 



much of the starch into sugar before its entrance to the mesen- 

 teron, since the secretion is poured out on the hypopharynx, 

 where it mingles with the food, and has then to traverse the 

 pharynx and long oesophagus before entering the mesenteron. 

 The oesophageal valve does not usually lie exactly beneath the 

 reservoir as shown for the sake of clearness in figure 3, but both 

 oesophagus and reservoir twist slightly near the valve, i. e., as 

 soon as they leave the thorax with its mass of muscles and enter 

 the abdomen and have more space, so that the valve and reservoir 

 generally lie somewhat on the right-hand side. 



The mesenteric musculature (fig. 4) consists of an inner transverse 

 and an outer longitudinal layer of rather slender fibres. In the 

 rectum this disposition of the muscles is reversed. 



The four malpighian tubes (fig. 3) for the greater part of their 

 length are plain, rather large diameter tubes, but the short distal 

 portion is of smaller diameter and lobulate, the cells of one side 

 alternating with those of the other. The nuclei of the main 

 portion are more or less globular, those of the distal portion long 

 or oval, but these latter sometimes become very irregular and 

 much branched, probably when actively secreting. This distal 

 part seems to secrete from the blood and excrete into the lumen 

 of the tube a resinous-waxy substance, allied to that of the cuticular 

 wax-glands; it was obtained by boiling several of the distal ends 

 in ether in a small test-tube. The whole tube is at times of a 

 hyaline appearance, of smaller diameter and in color pale yellowish. 

 Generally the main portion is opaque white and often greatly 

 distended for its whole length with urates, calcium oxalate and 

 other waste products, whilst these are not found in the distal 

 portion, which always remains hyaline. The proximal part of 

 the tube, just at its entrance to the gut, somewhat resembles the 

 distal part. The tubes are covered externally by peritoneal mem- 

 brane, with a few elastic fibres and tracheae; they have a chi- 

 tinous basement-membrane, apparently secreted by the epithelium 

 which rests upon it; the lumen of the tube is lined by a thick 

 chitinous secretion of the epithelial cells, and has a distinctly 

 striated appearance. When treated with potash and examined 

 under a high power, the intima is seen to be creased or furrowed 

 longitudinally, so that it has the appearance of being formed of 

 six strands fused together spirally — much like a piece of rope. 



