.DIGESTIVE SYSTEM 113 



III. DISSECTION OF THE DIGESTIVE SYSTEM. 



Cut away the part of the collar to the left of the pul- 

 monary aperture. Detach the right side of the collar, with 

 the anal aperture, from the body-wall. Separate the rectum 

 from the body by cutting along the right side of the mantle, 

 just to the left of the rectum, as far back as thz hinder end of 

 the mantle-cavity. Turn the rectum back, and pin it down. 



Make a median longitudinal incision through the floor of 

 the mantle-cavity, and continue it forwards along the head to 

 its anterior end. Dissect the flaps away from the underlying 

 parts, and pin them out right and left. 



Carefully dissect off the thin skin covering the spiral 

 visceral mass ; and unravel the reproductive organs, which 

 are white in colour and very bulky, and the alimentary canal, 

 the coils of which are very intimately connected with the liver. 



Arrange the reproductive organs on the right, the digestive 

 organs on the left side of the dissection. 



The removal of the integument from the visceral mass 

 requires care, but presents no great difficulty. Special care is 

 needed at the posterior end of the mantle- cavity , where the 

 parts are rather firmly bound together. 



The dissection is greatly facilitated by frequent washing 

 under the tap. 



A. The Alimentary Canal. 



The alimentary canal is a convoluted tube, of nearly 

 uniform size along the greater part of its length, but presenting 

 special features in its anterior portion. 



FIG. 23. Helix pomatia. Dissection from the right side to show the 

 digestive and reproductive systems. (A. M. M.) 



A, anus. AG, albumen gland. B, buccal mass. C, sac of odontophore. 

 CG, cerebral ganglion. D, jaw. E, mouth. F, flagellum. G, genital 

 aperture. H, crop. HD, hermaphrodite duct. HGr, hermaphrodite gland. 

 I, intestine. K, dart sac. L, mucous glands. LD, left bile-duct. LL, left 

 lobe of liver. M, female portion of the common duct. N, male portion of 

 the common duct. 0,'receptaeulum seminis. O', dilated end of receptaculum 

 seminis. P, penis. PG, pedal ganglion. R, rectum. RD, right bile-duct. 

 BL, right lobe of liver. S, 'stomach.' SD, salivary duct. SG, salivary 

 gland. T, tentacle. VD, vas deferens. VG, visceral ganglion. Y, eye. 

 Z, posterior end of foot. 



I 



