344 ORGANS OF DIGESTION'. 



to the anus, where distinct levator and sphincter muscles 

 are perceptible. The exterior of this intestinal portion, 

 from the stomach to near the anus, is surrounded with small 

 short biliary follicles, generally filled with their yellowish- 

 brown coloured secretion. The whole alimentary canal of this 

 animal is commonly found filled with the moist black earthy 

 soil in which it lives, and which it incessantly conveys 

 through its body to derive nourishment from the organized 

 particles so abundant in that matter. The alimentary canal 

 is more tortuous in its course, more capacious throughout, 

 with its gastric portion less distinctly marked, in the delicate 

 transparent short body of the pectinaria, and even in the 

 long distensible trunk of the arenicola, which, like many 

 other worms and echinoderma, transmit incessantly the 

 moist sands of the sea through their intestine, to extract 

 as food the innumerable minute animals contained in that 

 medium. The coriaceous lining is seen in the lower portion 

 of the more lengthened stomach of the arenicola, as in the 

 earth-w r orm ; and below this part are the openings of two 

 yellow-coloured biliary follicles, lengthened in form like 

 those of insects. Within the muscular sucking disk of the 

 mouth, in the medicinal leech, there are three crescentic 

 horny jaws, supporting each a row of sharp acuminated 

 teeth, with which it files its triradiate wound. The intestine 

 passes straight through the long axis of the body, sacculated 

 in a regular manner, and furnished with short wide lateral coeca, 

 nearly throughout its whole course. There are ten of these 

 coeca on each side, and smaller enlargements of the intestine 

 are interposed between each pair ; the coeca increase gradually 

 in size from the first or anterior to the ninth pair ; and the 

 two posterior coeca, which are much larger than any of the 

 others, extend backwards along sides of the remaining 

 short portion of the intestine. This sacculated part of the 

 intestine occupies about two thirds of its whole length, 

 and terminates, like a stomach, in the succeeding straight 

 portion, by a narrow elongated valvular pylorus. The short 

 and wide oesophagus is marked internally with longitudinal 

 plicae of its mucous coat, and the duodenal portion of the 

 intestine, beyond the pyloric valve of the long sacculated sto- 

 mach, is furnished with numerous transverse folds confined 

 also to its inner membrane. The colon enlarges into a small 

 round sac before it reaches the anus. The number of the gas- 



