22 G L A N D U L A R O R G A N S AND
upper part hear the eyes there are upwards of thirty fmall duds fent off, which
open upon the furface of tlie Hcin. The liquor difcharged from thefe has nearly
the fame degree of vifddity as the fynovia in man.
But befides the very pidlurcfque du& I have been defcnbing, I have remarked,
on each fide of the fifli, a little farther forwards than the foremoft of the five
breathing holes, a central part (¿), from which a prodigious number of duds
ilTues, to terminate on almoft the whole furface of the ikin, excepting only the
fnout or upper jaw. At thefe centres all the duds are i luit; and iri their courfe
they have no communication with each other (c). In thefe two central parts,
or on the beginning of the mucous duels, a pair of nei-ves (¿Z), nearly as large as
the optic, terminate; and, which is a curious circumftance with rcfped to
them, they are white and opake in their courfe between the brain and thefe
d u f t s ; but when they divide, they become fuddenly fo pellucid, that it is impoflible
to trace them farther,, or to diftinguiili them from the coats of the
dufts.
T h e mucus of thefe dudls is fo extremely vifcid, that it is difficult to fqueezc
it out.
WHEN we review the preceding defcription, we obferve,
i j l , Not only a veiy elegant ftrudare for the preparation of the mucus;
but,
2d/y, Such a fudden change of the colour of a nerve, that we are tempted to
infer, that its continuation is not merely an expanfion of the matter of the brain,
but that the texture of the nerve is altered in its courfe.
3^7)', We fee clear proof, that fome, at leaft, of the organs of fecretion, are
fo far from being remarkable for the fmallnefs of their nerves, that an uncommon
ihare of nervous energy feems neceflary for them, to enable their vcffcls to feparate
and change the liquors they fecrete.
Oy the Liquors fecreted into the Cavities of the Cranium, Pericardium^ and Abdomen.
J T has been long known, that in the greater number of iiihes a watery iquor
is found in confiderable quantity within the head, between the dura and pia
mater: but the nature of that liquor has not been fufficiently attended to, nor
are its ufes in the olTeous fillies fully underftood.
T h e cavities of the pericardium and peritoneum in all fiilies have been fuppofed
by authors to be iliut facs.
But in the ikate and ilurgeon I have obferved fome circumilances, both with
refpecl to thefe cavities and the liquors they contain, that well merit attention.
I. in
(i) See Tab. VI. and VII. p. 9. (<r) Tab. VI. and VII. io. M. 12. 13. 14. ly. (rf) Tab. VII. 16. .7.
S E C R E T E D L I Q_U O R S IN FISHES.
1. In the firil: place, the liquor within the head (/) is of a faltiili tafte ; and
not lefs than one fixty-fifth part of its weight is owing to fea-falt diffolved in it ;
or it contains nearly one half of the proportional quanrity of fait diflblved in our
fca-water.
2. Within the cavity of the abdomen or peritoneum of a ikate, a great quant
i ty of a fimilar liquor is to be found, but containing fomewhat lefs of the fait
or about one feventy-eighth part (y).
3. The great quantity and evidently fait tafte of the liquor of the abdomen,
which I remarked before I examined the liquor within the head, led me to look
for palTages by which I fufpected the fea-water might get into the abdomen; and
I foon found two holes or palTages, one at each fide of the anus, through which
a goofe-quill may be paffed {¿), One thing, however, ftruck me, that within
each of thefe paiTages, there is a femilunar membrane or valve, fo placed as to
allow liquors to get out from the abdomen readily, but to refill fomcwhat'their
entrance into it
4. Further,' I difcovered, that in the Ikate the bottom of the pericardium is
lengthened into the fliape of a funnel, which divides into two branches, which
are tied clofely to the lower part of the cefophagus, and open into the clvity of
the Abdomen (;). From the obliquity of thefe branches, and their intimate adhefion
to the cefophagus,. neither air nor water can be forced into them from the
abdomen: Hence, unlefs we fuppofe that in the living animal they take up the
fluid from the abdomen, in the way our punfta lachrymalia take up the tears,
which is highly improbable, we mull conclude that they ferve to convey thé
liquor of the pericardium into the cavity of the abdomen.
5 . In the Sturgeon, I have likewife found two holes or palîàges at the fides of
tlie anus fimilar to thofe of the Ikate : but, further, I have in this fiih obferved
a large funnel on each fide of the abdomen, which at its bottom opens
into the middle of the pelvis of the correfponding kidney (/).
WHEN we review the foregoing obfcrvriflons, we are led to fuppofe,
1. That the liquor of the pericardium of the ikate palTes, through the funnel
and du£ls defcribed, into the cavity of the abdomen.
2. We can have little or no doubt that the liquor in the abdomen of the
fliirgeon paflis into the pelvis of the kidney; for we cannot fuppofe that the
urine paffes through the holes defcribed into the cavity of the abdomen, as the
pelves have large openings into the common cloaca, as in other fillies.
3. In like manner, confidering the funnel iliape of the lower parts of the abdomen,
and of the paffages at the fides of the anus of the ikate, and difpofition
o f
(0 s<e ¡n Tab. XXXIV. 11,0 fiic of llie cavily of the cr
t/O The qiiaiitily of rea-falt conuinid In tlicfc liquors w
tlicifortl. OLLE lini onìy WIS esiimined.
(.C) Tflb. XVIII. 19. 30. aiidTab. XIX. 26.
(0 Tab. II. 1!. II. 23. 23. 2.3. AND Tab. XVIII. I
(/J Tab. VIlttÌB, 1. N. 0. P.
It mjr rcquifi, examined by my learned and 3<
Tab. XVIII. 30.
(i) Tab. VIII. Sj. ,. Q^R. S, and Kj . .. Q. R.