34^ PHILOSOPHY OF ZOOLOGY. 



The termination of the lymphatic veins in the skin, may 

 be readily ascertained in this class. Coloured liquors in- 

 jected into them, are discharged by numerous pores, chiefly 

 situate on the upper parts of the body. These orifices 

 are placed at regular intervals. As Dr Monro did not ob- 

 serve any appearance of extravasation in the cellular sub- 

 stance, he considered that these orifices were the natural 

 beginnings of the lymphatic veins. 



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 recep- 

 tacles, situate 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 receptacles, and 

 which have their extremities contracted by a doubling of their internal mem- 

 branes, 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 rather plexus of 

 vessels, brings the lymph from the brain and organs of the senses, and from 

 the mouth, jaws, and gills. 



" These receptacles may therefore be called the common receptacles of the 

 chyle and lymph. The right receptacle communicates freely with the left 

 by large canals, which pass chiefly behind the heart and oesophagus. 



" From each of these receptacles in the salmon, a canal runs downwards 

 and inwards, and opens into the upper end of its corresponding vena cava 

 inferior, contiguous to, and on the fore and outer side of the internal jugular 

 vein. The termination of these canals are contracted, and their internal 

 membranes are doubled, so as to serve the purpose of valves, in preventing 

 the passage of the blood from the venas cavaj into the receptacles. In the 

 cod kind, the receptacles are proportionally larger than in the salmon ; and, 

 besides transmitting the muscles of the gills, and their several nerves, con- 

 tain the upper cornua of the air-bladder." — (Monro, Struct, and Ph}/s. of 

 Fishes, p. 31.) 



