ICHTHYOLOGY. 



677 



of Kuhn. 



Or .--..- ;M 



liTCt. 



parallel to each other, and near the mesenteric arteries. 

 In their whole course, they communicate by a vast num- 

 ber of small transverse canals. At the top of the abdo- 

 men near the gall bladder, the lacteals of the stomach, 

 and lymphatics of the spleen, liver, and intestinula coeca 

 are added. The chyle, mixed with the lymph of the 

 assistant chylopoietic viscera, passes upwards and to- 

 wards the right side into a large receptacle contiguous 

 to the gall bladder, and between it and the right side 

 and back part of the lower end of the oesophagus. From 

 the receptacle of the chyle, large canals pass upwards 

 to the right and left, receiving in this course the lymph 

 from the organs of urine and generation. Those on the 

 left side are chiefly behind the oesophagus. 



The chyle, mixed with the abdominal lymph, having 

 ascended above the bones, which resemble our clavicles, 

 is poured into large cellular receptacles, situated chiefly 

 between the clavicles and the undermost of the gills, 

 and which also receive the lymph from all the other 

 parts of the body. 



Four lymphatic vessels, which terminate in these re- 

 ceptacles, and which have their extremities contracted 

 by a doubling of their internal membranes, chiefly 

 merit attention. The first conveys the lymph from the 

 middle of the belly, from the ventral and pectoral fins, 

 and from the heart. The second runs up the side of 

 the fish, parallel to the great mucous duct, and brings the 

 lymph from the principal muscles of the tail and body. 

 The third is deep seated, and conveys the lymph from 

 the spine, spinal marrow, and upper part of the head. 

 The fourth lymphatic vessel, or rattier plexus of vessels, 

 brings the lymph from the brain and organs of the sen- 

 ses, and from the mouth, jaws, and gills. 



These receptacles may therefore be called the com- 

 mon receptacles of the chyle and lymph. The right 

 receptacle communicates freely with the left by large 

 canals, which pass chiefly behind the heart and oeso- 



i each of these receptacles in the salmon, a canal 

 runs downwards and inwards, and opens into the up- 

 per end of its corresponding vena cava inferior, conti- 

 guous to, and on the fore and outer side of the internal 

 jugular vein. The termination of these canals are con- 

 tracted, and their internal membranrs are doubled, so 

 as to serve the purpose of valves, in preventing the pas- 

 sage of the blood from the vena* cavsc into the recepta- 

 cle*. In the cod kind, the receptacles are proportion- 

 ally larger than in the salmon ; and, besides transmit- 

 ting the muscle* of the gills, and their several nerves, 

 contain the upper cornua of the air bladder." ( Monro, 

 Struct and Phyi. of Fuhft.p. SI.) 



The termination of the lymphatic veins in the skin, 

 may be readily ascertained in this class. Coloured li- 

 quors injected into them, are discharged by numerous 

 pore*, chiefly situated on the upper parts of the body. 

 These orifices are placed at regular intervals. Ai Dr 

 Monro did not observe any appearance of extravasation 

 in the cellular substance, he considered that these orifi- 

 ce* were the natural beginnings of the lymphatic veins. 



SICT. X. Organs of Secretion. 



In oomidrring the organs of this class, we propose 

 to examine the structure of the liver, pancreas, kidneys, 

 air, and mucous ducts. 



1. Lher This organ in fishes, is remarkable on ac- 

 count of its site in proportion to the rest of the body. 

 It commonly lies almost wholly on the left side. Its 

 ttlow exhibits various shades of brown frequently mix* 



Structure 



and 



Functions 

 of Fishes. 



ed with yellow. It is entire in some fishes, as the lam- 

 prey, flsunder, and salmon; or divided into two or 

 more lobes, as in the perch and carp. These varieties 

 of form are constant in all the individuals of the same 

 species, but frequently differ somewhat in the species 

 of the same genus. 



The gall bladder is present in the greater number of 

 fishes ; but in a few species, as the lamprey, its presence 

 has not been detected. The bile varies greatly in co- 

 lour according to the species. In the thornback and 

 salmon it is yellowish white, and, when evaporated, 

 leaves a matter which has a very sweet and slightly 

 acrid taste, containing no resin. The bile of the carp 

 and eel is very green and very bitter, contains little or 

 no albumen, but yields soda, resin, and a sweet acrid 

 matter similar to that which may be obtained from sal- 

 mon bile, The biliary ducts open separately into the 

 intestine. 



The liver appears to be the only organ of the body 

 of fishes which contains oil in abundance, or is sought 

 after on that account This oil is lodged in cells, and 

 cannot be completely obtained by the boiling of the li- 

 ver. To accomplish the extraction of the whole oil, 

 fishermen in general allow the livers to putrefy a little, 

 and in this manner the cells are ruptured, and a greater 

 quantity of oil obtained. But gelatinous matter and 

 bile are likewise among the products, and as these af 

 terwards putrefy, they communicate a foetid smell to 

 the oil. This disagreeable smell is common to all kinds 

 of fish oil thus prepared ; but it may be removed by 

 various processes. Perhaps the best are those which 

 were communicated to the Society for the encourage- 

 ment of arts, manufactures, and commerce in the year 

 1761, and published in the twentieth volume of their 

 Transactions, to which we refer the reader. The liver 

 of the cod, cut into small pieces, lioiled in the stomach 

 of the same animal, ar.d eaten with vinegar and pepper, 

 is a favourite dish in the northern islands of Scotland. 



2 Pancreas. In thechondropterygii, there is a pan- Pancreas. 

 creas resembling that in the higher classes of animals, 

 of an irregular form, and placed at the origin of the 

 intestines. The substance appears compact, but gela- 

 tinous when cut. In the osseous fishes, the intestinula 

 coeca already descrilx-d, appear to serve instead of a 

 pancreas. They send two large canals into the intes- 

 tines ; and when these are wanting, as is the case in 

 the carp, the walls of the intestines discharge abun- 

 dance of humour from glands placed upon their inner 

 surface. In the sturgeon, an organ is found, in its in- 

 ternal structure similar to these intestinula ; but in its 

 outward form resembling the pancreas of the skate. It 

 is inclosed in a muscle, evidently intended to express 

 its contents. It opens into the intestine by three large 

 orifices, and has internally a singular rrticular appear- 

 ance, as exhibited by Monro in the work on fishes so 

 often referred to, page 84. tab. ix. 



3. Spleen. This organ varies greatly in its form and spleen. 

 position in the animals of this class. In some it is 

 nearly triangular, while in others it approaches to a sphe- 

 rical figure. It is in general entire ; in some instances, 

 however, it is divided into lobes, which adhere by very 

 slender filaments. In the sturgeon, these lobes are se- 

 ven in number. It is placed in some species on the 

 stomach, or to the first part of the intestines ; in others 

 between the stomach and liver ; and in a great number 



it is under the air bag, and above the other bowels. 

 It is always of a darker colour than the liver. 



4. Kidneys. It was the opinion of Rondeletius and Kidneys. 

 others, that fishes were destitute of kidneys and the 



