[387] 



ALIMENTARY CANAL, LIVER, PANCREAS, 



AND AIR-BLADDER OF AMIURUS CATUS. 



BY A. B. MACALLUM, B.A. 



[Read before the Canadian Institute, April the 5th, ISSi..] 



THE ALIMENTARY CANAL. 



COARSE ANATOMY. 



The cavity of the mouth is very capacious. Its entrance is guarded 

 "by plates of teeth situated on the maxillaries above and on the 

 mandibles below. These are the only regions of the mouth where 

 teeth are found. In front of them above and below along the 

 margin of the mouth portions of skin, frequently pale or discolored, 

 are transitional between the outer skin and the membrane of the 

 mouth, and function as lips. 



Behind the pads of teeth and running concentrically with them 

 are folds, one above and one below, arising from a relaxation of the 

 lining membrane ; that behind the maxillae is largest, but both may 

 be absent. In one specimen of Amiurus nigricans, the fold reached 

 downward and backward into the cavity of the mouth fully one-half 

 inch. 



The lining membrane of the mouth is generally colorless. That 

 •of the sunken palate may have a dark color. When hardened the 

 membrane shows minute blotches on a white ground, caused by 

 beaker organs (taste-buds ]) and the vascular papilla? of the subjacent 

 tissue. 



The ' tongue ' is most distinctly observable when the hyoid bone 

 is pushed up by the finger from below, and is then an oblong flat- 

 tened elevation. A ridge or rather a row of papillae runs medially 

 over its surface backward into the pharynx. This is the seat of 

 numerous beaker organs, especially in the young cat-fish. 



The palate is sunk from the maxilla? and is divided into two 

 shallow depressions by the parasphenoid. 



The surface of the pharyngeal floor anteriorly inclines on each 

 side somewhat towai-d the base of the srill arches. 



