170 
On the Respiratory Organs and Air Bladder 
£ J UNE 
plates, and consists of a thick solid tissue, having a curled margin, not unlike that 
of the common species of alga, or sea- weed. The branchial artery having given off 
branches to the laminae of the arches, runs for a short distance in a canal of the 
osseous plate, which is connected with the anterior arch, and afterwards proceeds 
upon its surface, where it divides and subdivides into minute branches, distributed 
to the tip of the supernumerary organ : the vessels that return the aerated blood 
unite into one branch, which joins those proceeding from the gills to form the aorta. 
Silurus Singio. Besides the eight branchial arches, there are in this tish two 
respiratory canals, which extend along the back from the cavity of the mouth to 
near the end of the tail, where they terminate in blind extremities. They are 
situate below the superior or dorsal portions of the lateral muscles, one on each 
side of the vertebrae, close to their spinous processes ; and are composed of two 
coats, of which the internal one is smooth, vascular, and of a thin delicate texture, 
resembling the membrane that covers the branchial laminae. Each of these canals 
is provided with a large vessel, which injection shews to be a continuation of that 
branch of the branchial artery sent to the posterior arch. It runs along the bot- 
tom of the canal, giving off, as it proceeds to its posterior extremity, numerous 
transverse branches that are minutely ramified upon its internal surface. The 
canals open into the mouth ; but the communication between them and that cavity, 
is in a great measure shut up by the laminae of the second and third arches, at the 
junction of their limbs : these laminae are disposed in a semicircular figure, and 
are so placed, in relation to each other, as to present, when the two arches are ap- 
proximated, a laminated surface, of an oval figure, to the mouth of each canal. 
The air contained in these cavities, is apparently separated from the water, by 
means of the laminated body : and the blood, thus oxygenated upon their internal 
surface, is conveyed by small vessels that descend between the transverse pro- 
cesses of the vertebrae, to join the aorta 1 . 
All the species, possessing these supernumerary organs of respiration, are very 
tenacious of life ; surviving the infliction of severe wounds, and living upon land 
for a much longer time than other fishes. “ In China, the species of the G. 
Ophiocephalus ,” according to Hamilton, <c are often carried alive in pails of water, 
and slices are cut for sale as wanted, the fish selling dear while it retains life, 
while what remains after death is considered of little value. 5 ’ The Coins Cobojius 
can be kept alive without water for five or six days, and, according to the same 
author, is often conveyed in that state to the Calcutta market, from marshes at the 
distance of one hundred and fifty miles. This species, and the Ophiocephalus 
Gachua, like the Doras Costata or hassar 2 , possess the power of locomotion on 
land to a considerable extent ; and are the fishes so often met with, after a shower 
of rain, in fields at a distance from rivers or marshes ; and hence supposed to fall 
from the clouds 3 . 
The air-bladder of fishes is generally found in the abdomen, adhering to the 
lower surface of the spine. In the Optiiocephalus Marulius and Gachua , however, 
it is not confined in its situation to that cavity, but extends as far as the extremi- 
ty of the tail, more than tw r o thirds of it being enclosed between the caudal portions 
of the lateral muscles. It is of a cylindrical shape, and is divided internally into 
two unequal cavities, hv a transverse septum, formed by a reflection of the internal 
coat 5 in the centre of which septum there is a small toramen surrounded by a 
number ot short radiated fibres, apparently of a muscular structure, allowing the 
air to pass from one compartment to the other. The external tunic, at the anterior 
or abdominal extremity of the organ, is apparently of a muscular texture, and is 
provided with a large nerve, derived from the eighth pair; but behind it is thin 
and weak, the powerful lateral muscles by which it is encased supplying its want 
of muscularity. J 
The same kind of internal division exists in the air-bladder of the Macrognathus 
Arviatus. In both of these fishes, the vascular body which, it is generally suppos- 
ed, secretes the air of the bladder, is situate on the internal surface of the anterior 
portion of the organ, and consists of several small kidney-shaped glands, with 
minute villi diverging from them. 
In the toius Cobojius it extends also as far as the end of the tail. Behind the 
oone that forms the boundary of the abdominal cavity, it is divided longitudinally 
* ^ open at both ends, be introduced through an ineision, at the side of the 
X l " e V ,llt0 one , 0 / l " ese canals, bubbles of air will arise from it simultaneously with 
mose disengaged from under the operculum. 
3 fj r - Hancock’s Zoological Journal, No. XIV. 
Hamilton’s Account of the Fishes of the Ganges, p. 63. 
