OF THE STURGEON. 
337 
the former rendering the inner surface of the oesophagus 
rough and irregular. The disposition of these pyramidal 
eminences and tubercles may be said to be both in trans- 
verse and in longitudinal rows. Of the latter, three are 
very distinct, and are separated by long furrows, the sur- 
face of which, as of that of the intervals between the emi- 
nences, is smooth, and of a more decided opaque pearly 
colour than the other portions of the membrane. Most of 
the papilla have acuminated apices, and some are bifid. 
They are firm and semicartilaginous in consistence. (PI. IV. 
Fig. 1.) 
These papillae are evidently intended to contribute to the 
mechanical division of the food. The sturgeon is destitute 
of teeth, and consequently swallows his food entire. The 
oesophagus contained, in the case of the individual dissected 
by me, several small fishes of the sand-eel genus {Ammody- 
tes Tobianus), which had been swallowed entire, and were 
destined, in all probability, to undergo a preliminary mecha- 
nical digestion in the interior of the tube. The thickness 
of the muscular layer shews that it possesses considerable 
contractile power ; and it is easy to see that the papillae and 
tubercles of the inner membrane, if forcibly rubbed against 
articles of food by this powerful agent, must quickly reduce 
them to fragments fitted to enter the stomach, and undergo 
the chemical solution of that organ. 
At the same time, I do not feel myself quite justified in 
asserting, that this apparatus must divide the food pre- 
vious to its transmission into the stomach ; for, in the latter 
organ, amidst much digested and dissolved food, were 
found also several small fishes, apparently sand-eels, still in 
a state of great integrity. 
These conical papillae and tubercles, nevertheless, with 
the opaque pearl-white aspect of the inner membrane, con- 
stitute the most distinct anatomical character of the oeso- 
voL. VI. y 
