NERVOUS SYSTEM 95 



4. The visceral or parieto-splanclmic ganglia are a pair 



of closely apposed ganglia, situated on the under 

 surface of the posterior adductor muscle about the 

 middle of its length. 



Pass a seeker into the cloacal cavity, and along the median 

 supra-branchial passage, and lay open this latter, if it has 

 not already been done. The visceral ganglia are then readily 

 found in the position noted above. 



From the gangUa nerves are distributed to the 

 posterior adductor, the mantle, and other parts. 



5. The cerebro-visceral connectives are a pair of long 



nerve- cords which connect the cerebral with the 

 visceral ganglia. 



From each cerebral ganghon the connective 

 curves upwards and backwards through the visceral 

 mass, lying close to the surface. It then runs 

 straight back along the inner surface of the kidney 

 to the visceral ganglion. The part in relation 

 with the kidney is very easy to dissect : in front of 

 the kidney the dissection is more troublesome, but 

 presents no serious difficulty. 



P. The Digestive System. 



1. The alimentary canal is a convoluted tube the greater 

 part of which lies in the visceral mass, imbedded in 

 the liver and generative organ, while the terminal 

 portion runs back through the pericardial cavity to 

 the anus. 



Insert a seeker into the mouth, and using this as a guide 

 slit up the oesophagus and stomach with scissors. Slit open 

 in a similar fashion the whole length of the intestine, begin- 

 ning at the rectum and working backwards to the stomach 

 {cf fig. 21, p. 21). 



a. The mouth lies immediately behind the anterior 

 adductor, and between the lips formed by the 

 palps : there are no jaws. The food, which con- 

 sists of minute organisms of various kinds, both 



