154 LYMPHATIC SYSTEM. 



lymphatics which make a network behind the heart, as is 

 above described. These last mentioned vessels receive the lym- 

 phatics from the anterior or superior part of the gills, and 

 from the fauces. The thoracic duct, after being joined by 

 these vessels, communicates with that network near the orbit ; 

 where its lymph is mixed with that of the lymphatics from the 

 posterior part of the gills, from the superior fins, belly, &c., and 

 then from this network a vessel gojes into the jugular vein, 

 just below the orbit. This last vessel, which I call the termi- 

 nation of the whole system, is very small in proportion to the 

 network from which it rises ; and indeed the lymphatics at this 

 part are so large as to exceed by far the size of the sangui- 

 ferous vessels. 



The thoracic duct of the left side, having passed under 

 the oesophagus from the right, runs on the inside of the 

 vena cava of the left side, receives a branch from its fellow of 

 the opposite side, and joins the large lymphatics which lie on the 

 left of the pericardium, and a part of those which lie behind 

 the heart, and afterwards makes, together with the lymphatics 

 from the gills, upper 'fins, and side of the fish, a network, 

 from which a vessel passes into the jugular vein of this side. 

 In a word, the lymphatics of the left side agree exactly with 

 those of the right, as above described. 



Besides these vessels, there is yet another part of the sys- 

 tem which is deeper seated, lying between the roots of the 

 spinal processes of the back-bone ; this part consists of a large 

 trunk, that begins from the lower part of the fish near the tail, 

 and as it ascends receives branches from the dorsal fins, and 

 from the adjacent parts of the body. It goes up near to the 

 head, and sends a branch to each thoracic duct, near the part 

 where these ducts come off from their common trunk. 



This description, though taken from a haddock, agrees, I 

 believe, pretty exactly with the distribution of those vessels in 

 the cod, whiting, and perhaps all other fish of the same shape. 



To this general description I shall add what I have observed 

 of the more striking peculiarities of this system in fish. 



In the first place, those vessels are remarkable in not having 

 any lymphatic glands, that I can discover, in any part of their 

 course. In this they agree with the turtle, but differ from 

 birds, which have lymphatic glands on the vessels of their 

 necks. 



