SHEATFISH. 
699 
into the small intestine, often in several small curves, above 
and behind the stomach. Here the intestine again bends 
forwards, below and to the left of the stomach, to about 
a line with the pylorus, then returns in a sharp curve, 
and proceeds to the vent. The liver is large, though 
its length varies: the left lobe is the longer, extends to 
about a line with the bottom of the stomach, sometimes 
not quite so far, sometimes much farther, and is divided 
at the tip into two secondary lobes of varying length “. 
The gall-bladder, which lies between the duodenum and 
the anterior part of the left lobe of the liver is saccate 
and large 6 . The pancreas 0 lies nearer the duodenum, 
in the shape of a horse-shoe with the prongs directed 
forwards and surrounding the gall-duct. The spleen is 
situated above the stomach, between this organ and the 
air-bladder, to the left of the first coil of the intestine 
and sometimes entirely in front of, sometimes half in 
front of and half behind and above the anterior angle 
of the last coil of the intestine. It is rounded (ellip- 
tical) and flattened' 6 . The structure of the large air- 
bladder is mentioned above 0 . The under surface of its 
posterior division is furnished with a longitudinal groove, 
at the anterior end of which the pneumatic duct de- 
scends into the oesophagus. The anterior end of the air- 
bladder is attached partly to the lower surface of the 
tip of the foremost, transverse processes (belonging to 
the second abdominal vertebra), partly to the anterior 
part of the side of the large vertebra which, as we have 
mentioned above, is produced by the coalescence of the 
original second, third, and fourth vertebrae. Within the 
latter fastening of the air-bladder lies the descending 
blade of the hindmost and largest, so-called acoustic 
bone ( malleus ), which is loosely folded in beside the 
large, composite vertebra. The second blade of this 
acoustic bone lies horizontally, pointing in a forward 
direction, at right angles to the descending blade, and 
glides along the under surface of the base of the first 
transverse process. This acoustic bone is thus both bent 
and twisted; and within the angle of the bend the base 
of the descending blade forms a free margin, which, when 
the bone is in its natural position, lies as a continuation 
of the upper margin of a lateral groove on the body of 
the vertebra. As only the third (hindmost) of the coa- 
lescent vertebrae is furnished with ribs, the so-called 
malleus thus corresponds to a rib of the middle ver- 
tebra (the third abdominal vertebra). The malleus co- 
heres at its inner anterior corner with the vertical, flat 
incus f , which should thus correspond (if this homology 
with the ribs should receive the corroboration it still 
requires from the history of development) to a rib 
of the foremost of the coalescent. vertebrae (the second 
abdominal vertebra). The first abdominal vertebra, which 
in the Sheatfish is separated both from the following 
vertebrae and the occipital bone, is without either trans- 
verse process or neural arch, unless these be represented 
on each side by the angular stapes , which is united by 
ligaments to the subjacent incus, and by the flat, 
but oblong claustrum, which lies above this point, is 
also united to the stapes, and covers the atrium sinus 
imparls on this side of the body. This atrium , which 
lies beside the spinal cord, is a lateral extension of the 
sinus impar situated in the occipital bone, a mem- 
branous, saccate extension of the cerebral membrane 
that lines the labyrinth. The anterior end of this sinus 
is furnished in the Carp-fishes 5 ’ — and probably here as 
well 6 — with a connecting duct between the sacculi of 
the labyrinth. The air-bladder is thus connected by 
means of the acoustic bones, not indeed immediately 
with the true hearing-apparatus, but with the lymphatic, 
subdural chamber that surrounds the latter. Modern 
scientists have therefore adopted the opinion 1 first main- 
tained by Hasse ; , and regard this connexion less as a 
conductor of sound than as a barometrical apparatus 
which conveys to the consciousness of these fishes a sense 
of the varying atmospheric pressure to which their air- 
bladder is exposed at different moments. 
“ In the above-mentioned specimen the length of the left lobe of the liver is 36'/ 2 cm. and its greatest breadth nearly 8 cm. The 
length of the right lobe is 14 x / 2 cm., its breadth nearly 5 cm. 
* In the specimen just mentioned the gall-bladder is about 14 cm. long and, when collapsed, about 6 1 /, cm. broad. 
c The length of this gland from the middle of the round posterior margin to the end of one of the prongs is (in the same speci- 
men) about equal to the breadth of the gall-bladder. 
d In the same specimen the spleen is 11 cm. long, 5 cm. broad, and about 8Y 2 mm. thick. 
e In the same specimen the air-bladder is 25 1 / 9 cm. long and rather more than 9 cm. broad. In a female 575 mm. long it is 89 
mm. long and 46 mm. broad. 
f Cf. Weber, De Aure et Auditu Hominis et Animalium , tab. V, fig. 30. 
g Cf. Nusbaum, Zoologischer Anzeiger, 1881, p. 553. 
h Cf. Retzius, Das Gehororgan der Wirbelthiere, I, p. 77, taf. XIII, fig. 1, si. 
1 Cf. Sagemehl, Morphol. Jahrbuch, X (1884), p. 14. 
j Anatomiscbe Studien , No. XIV, p. 596. 
