OF THE STUUGEON. 
341 
great and rather sudden changes of capacity ; and, from 
the voracity of fishes, which gorge, in general, until not 
only the stomach, but the oesophagus, is actually crammed 
to the throat, this viscus is, in these animals, occasionally 
stretched to a very great degree. When the muscular 
coat is stretched, if not beyond its bounds, it naturally 
contracts when the distending cause ceases to operate ; 
and even the distention, in this case, is not altogether unfa- 
vourable to its action. The peritoneum also, we know 
from the phenomena of uterogestation, is both distensible 
and contractile. With the mucous membrane, however, 
it appears to be different ; and the only mode by which 
this tissue seems with safety to undergo alternate disten- 
tion and contraction, is by its being provided with greater 
actual extent, and by the contractile power of the enclosing 
muscular layer, drawing it into folds of various size and in 
different directions. The reason why these folds are lon- 
gitudinal in the sturgeon, is, that the muscular layer is ar- 
ranged in circular fibres round the axis of the stomach. 
Towards the pyloric end the villous coat becomes firm, 
and the muscular layer acquires extraordinary thickness 
and strength, approaching to fully half an inch of solid 
muscular substance, at one inch from the pyloric termina- 
tion. At the same time the organ contracts, tapering like 
the apex of a cone, and, after making a slight bend, forms 
the pyloric orifice, which terminates in the duodenum by a 
valvular opening of peculiar figure and structure. This 
consists in the muscular and mucous tissue being contracted 
into a tubular opening, so much that the tip of the little 
finger may be inserted from the gastric end, but cannot be 
carried through. This opening, indeed, is so small, that it 
allows only a good sized pencil to be introduced. The 
pyloric opening is thus formed into an annular tube, which 
not only, by a further bend, completes the arch partially 
