176 
On the Respiratory Organs , SfC. of Fishes. 
£June 
to perform, in some degree, the function of the glottis, and thus produce a 
slight hissing noise, as may occasionally be heard, when the air is forcibly 
expelled from the bladder. The heart is situate upon the inferior surface of 
the esophagus, close to its termination at the stomach ; and from the ex- 
treme proportional length of that tube, is at a much greater distance from the 
organs of respiration than is the case in tishes. It consists of two cavities, an 
auricle, and a ventricle, provided with a thin membranous valve between them. 
The former receives all the blood of the body by four large vessels, viz. two veins 
conveying it from the head and anterior parts; one from the liver ; and one from 
the muscles of the posterior portion of the spine, the organs of generation, and the 
other viscera of the abdomen. The first run close to the spinal column, one on 
each side, and are joined by a transverse branch opposite to the 12th vertebra: 
they afterwards separate, and proceed, one in a straight direction, the other across 
the inferior surface of the esophagus to terminate in the auricle. The posterior cava, 
which is the largest of all, proceeds along the inferior surface of the spine, between the 
kidnies, to its destination; while the cava hepatica, after piercing the pericardium 
at its posterior part, runs for some distance within the cavity before it terminates 
in the auricle. The ventricle is of a conical shape, of a reticulated appearance in- 
ternally, and possesses two sigmoid valves at the origin of the branchial artery. The 
latter arises from it by an elongated bulb, of an oval figure, and measures from two and 
a half to three inches in length. It extends along the inferior surface of the esophagus, 
and divides, opposite to the posterior branchial arches, into three branches of an equal 
size. I woof these branches run, one on each side, between the fourth or posterior arch 
and the small bone connected with deglutition, as far as the vertebral extremity of the 
inferior limb of the former ; and being there reflected backwards, unite at an 
acute angle, opposite to the 10th vertebra, to form the aorta. The third branch, 
which is the continuation of the artery, proceeds along the under surface of the 
arches, and gives oft', in its course, a branch to the second and third of each side : 
it then runs forward as far as the os hyoiiles , and is ultimately expended upon the 
respiratory bladders. The small branches of the second and third arches, after sup- 
plying the lamina; of the former and the semi-transparent tissue of the latter with 
small twigs, are also continued to the bladders ; where they are minutely ramified, 
forming an indistinct net-work of vessels upon their internal surface. Fine ver- 
milion injection, thrown in at the root of the branchial artery, penetrates these 
minute vessels distributed upon the second and third arches and the internal surface 
* e bladders, while at the same time it fills the aorta and its branches as far as 
ie ai i’ aerated blood is returned by small vessels, forming, at the posterior 
pai ot the bladders, two short trunks, which join the branches of the branchial 
ar ,. t ' r - v f iore th . e y are reflected backwards, and unite to constitute the aorta. 
ie C uchia, it is obvious from this account of its anatomical structure, possess- 
es ie circulation of reptiles, and the respiration, partly of that class of animals, 
and partly ot fashes. Of the whole volume of blood contained in the branchial 
attery, one-third passes through the gills and respiratory bladders, while the other 
two are conveyed directly from the heart to the aorta, without being exposed to 
ne action ot the air. This fluid, therefore, undergoes a partial oxygenation, pre- 
senting, as may be inferred, a dark purple colour in both divisions of the vascular 
system, the arteries as well as the veins. Hence the obtuseness of the external 
senses, and want of activity observable in the Cuchia. It is of a dull and languid 
nature, exhibiting in all its movements a degree of sluggishness that forms a 
striking contrast to the vivacity of the eel. A few individuals, which I kept in 
water for upwards ot two months, during the last rainy season, were observed to 
lie at the bottom ot the vessel in a very weak and apparently torpid state, without 
idKing any food : and seldom moved about, except occasionally to rise to the 
i ace tor the purpose ot inhaling air. The respiratory bladders, although indivi- 
a y°* a small size, aftord, in conjunction with the branchial structure of the 
and third arches, a sufficient extent of surface for the oxygenation of the 
la . P°j tion ^ ie blood transmitted to them. They do not approach either in 
t.. n o. uiatlon tex tare to any known modification of branchiae, but on the con- 
ai y lave a close similitude, in both these particulars, to the posterior portion of 
Th ? r VCr Which the ani,llal Possesses of distending them 
the wot ’r fn th llUd ’ and the necessit y il ls «“der, of risia S to the surface of 
tion of I.. 1 S m UC ? ur P° se > P rove beyond a doubt that they perform the func- 
Phibioj^’, and / e;id us t0 the conclusion, therefore, that the Cuchia is “am- 
were betxv^nth ff? se “ se °* the word,— forming a connecting link, as it 
^caTiMj/,^7a3oi rej,tik5 ’ and ““ seaus Of fish®. 
