982 
tube passing directly from the stomach to the 
anus. In the Mullets ( Mugil), on the con- 
trary, the intestine is of great length and is very 
curiously folded, being intervolved with the 
folds of the liver so as to form a mass of trian- 
gular form moulded to the shape of the abdo- 
minal cavity, and affording an example of the 
longest and, in its disposition, the most complex 
intestinal canal of any of the class. 
This arrangement, as Kathke very justly ob- 
serves, is an obvious approximation to the dis- 
sition of the viscera most generally met with 
in molluscous animals, in which the folds of 
the intestine are prolonged into and almost bu- 
tied among the folds of their very large liver. 
In the Electric Eel (Gymnotus electricus ) 
the disposition and termination of the intestinal: 
tube is curious. First descending to the lower 
end of the stomach, it passes to the left side 
and ascends again as far as the esophagus ; it 
then winds downwards and backwards so as to 
encircle the stomach, and, lastly, advancing for- 
wards along the ventral aspect of the abdomen, 
it terminates, as in the Cephalopoda, beneath 
the throat, in the immediate vicinity of the 
heart and root of the tongue. 
No fish has anything like a colon or cecum. 
The only distinction between small and large 
intestines is met with just at the termination of 
the alimentary tube, where it opens into a kind 
of cloacal cavity, usually called the rectum. At 
this point there is generally a prominent cir- 
cular fold of the lining membrane constituting 
a kind of valve. In the Salmon several of these 
valvular zones succeed each other, giving to this 
part of the gut an appearance similar to that of 
the intestine of the Plagiostome cartilaginous 
Fishes immediately to be described. 
In the Sharks and Rays, the Plagiostomes 
Fig. 519. — 
Alimentary canal of Shark. 
a, cesophugus ; b, b, cavity of stomach, at the 
commencement of which are placed the valvular 
fringes mentioned in the text; c, passage leading to 
pylorus; d, spleen; e, pyloric cavity; f, dilated 
chamber ; g, h, bile-ducts; i, orifice of pancreatic 
duct ; k, k, valvular intestine. 
PISCES. 
just referred to, and also in the Sturgeon, the 
intestine presents a very remarkable structure. 
Externally it resembles a wide bag nearly simi- 
lar in shape and size to the stomach itself, and 
so short and stunted that, without some special 
arrangement, obviously a sufficient surface 
would not be afforded for the re mt of the 
nutritious portions of the food. By the me-— 
chanism adopted, however, this is abundantly 
provided. of the © 
roughout the whole bm 
gut the mucous membrane is arranged in deep 
spiral folds (fig. 519), which wind from end to 
end, only leaving a small orifice in the centre of 
each valvular projection, whereby the different © 
compartments formed between the spiral lamina — 
can communicate with each other, so that the 
digested food by this unusual arrai t is 
spread over a very great superficial area, and all 
e benefits of a long and convoluted intestinal 
tube are secured. Each fold of this extensive 
spiral valve contains between the layers of mu=— 
cous membrane that compose it an elastic 
substance, whereby it is kept constantly spread 
,out and restored to its orginal position when 
displaced by the passage of food through the 
central channel that permeates the whole series. 
In the Sturgeons a similar valve exists, bul 
its spiral folds are not so closely arranged: the 
intestine, moreover, is remarkable on 
of the great thickness of its muscular and in- 
ternal tunics, the latter of which presents 
reticulated or honey-combed appearance, thi 
larger meshes including irregular spaces, whic 
are again subdivided into smaller cells. Sligh 
vestiges of the spiral intestinal valve are visibl 
even in the Lamprey. 4 
Salivary glands—From the circumstance 
under which Fishes swallow their food, th 
presence of any sali rd Be is evidentl 
uncalled for; no fish, therefore, 
salivary glands. Nevertheless, in the Cypr 
nide and some other races the whole palate 
covered with a soft spongy substance, fic 
which a kind of mucosity is discharged throug 
imperceptible pores, which has been regarde 
by Rathke and others as a salivary orgar 
Cuvier, however, denies the glandular charae 
of this substance, regarding it as a peculiar at 
highly sensible tissue destined to be the seat 
a sense more or less analogous to that of ta 
—a supposition that is rendered more proba 
from the great number of nerves that enter 
substance. 
Pancreas—In the osseous Fishes no- 
creas, such as that met with in the hi 
classes of vertebrate animals, exists; i 
however, represented by a variable numb 
cecal sd begirn doe which open into the du 
num in the vicinity of the pylorus. Thel 
membrane of these pyloric caeca is of a 
dular character, and secretes an abund: 
a thin glairy fluid analogous to the pane 
secretion. The existence of the appendagi 
uestion is, however, by no means cons 
thus in the Labride, the Siluride, the Cyp 
nide, and many members of the pike 
they are altogether wanting. When 
moreover, their number varies very remark 
in different Fishes ; thus, sometimes, as 1 
count 
