SENSE ORGANS 263 



dorsal and ventral surfaces of the head. The tubes are filled 

 with a transparent gelatinous matter, which can readily be 

 squeezed out from their openings on pressure. 



Their function is not known with certainty, but they are 

 generally believed to be sense organs of some kind. The nerves 

 supplying them are the ophthalmic branches of the fifth and 

 seventh nerves, and the maxillary division of the fifth. 



Squeeze the head of a fresh specimen, so as to make the 

 gelatinous matter exude, and so render the openings visible. 



Bemove the skin from the dorsal and ventral surfaces of the 

 head, an operation much facilitated by dipping the head into 

 hot water for a few moments : identify the masses of ampullae 

 and the nerves in connection with them, and trace the tubes 

 outwards and backwards to their openings. Some of the tubes 

 which run along the dorsal surface of the skull, between the 

 cranium and the orbit, are some inches in length. 



Cut out a small piece of the mass of ampullm : put it on a 

 slide in a drop of water : separate the parts with needles : 

 cover, and examine under the microscope. Note the ampulla, 

 their internal divisions, the nerves supplying them, and the 



