vol,. LVIII.] PHILOSOPHICAL TRANSACTIONS. 557 



most acute anatomists had not been able to find in any bird the least appearance 

 either of those vessels or glands. The difficulty of discovering the lacteals in 

 birds was no doubt principally owing to the transparency, or want of colour, in 

 the fluid which they contain. In quadrupeds the lacteals are easily found, as 

 they are filled with chyle, which is mostly opaque and white ; whereas in birds 

 the chyle is as pellucid and colourless as the vessels themselves. The want of 

 mesenteric glands was another cause of our remaining so long ignorant of those 

 vessels. 



This system may be divided in birds, as it is in quadrupeds, into the branches, 

 viz. the lacteals and lymphatics, and their trunk, or thoracic duct. The lacteals 

 indeed, in the strictest sense, are in birds the lymphatics of the intestines, and 

 like the other lymphatics carry a transparent lymph. And instead of one thoracic 

 duct there are two, of which one goes to each jugular vein. In these circum- 

 stances it would seem that birds differ from quadrupeds, so far at least as he 

 could judge from the dissection of a goose, which was the bird he chose as most 

 proper for this inquiry. 



So much being premised, he next gives a description of what he had seen of 

 those vessels in this fowl ; and to illustrate the description he adds a figure from 

 the same subject, in which those vessels were filled with quicksilver. The lac- 

 teals run from the intestines on the mesenteric vessels. Those of the duodenum 

 (a) * pass by the side of the pancreas (a), -f- and probably receive its lymphatics: 

 afterwards they get upon the coeliac artery, of which the superior mesenteric is 

 a branch. While they are upon this artery they are joined by the lymphatics 

 from the liver (b) : here they form a plexus, which surrounds the coeliac artery 

 (cc) ; at this part they receive a lymphatic from the gizzard (d) ; and a little far- 

 ther, another from the lower or glandular part of the oesophagus (e). Having 

 now got to the root of the coeliac artery, they are joined by the lymphatics from 

 the renal capsulae ; and near the same part, by the lacteals from the other small 

 intestines, which vessels accompany the lower mesenteric artery. These last- 

 mentioned lacteals, before they join those from the duodenum, receive from the 

 rectum a lymphatic, which runs with the blood-vessels of that gut. Into this 

 lymphatic some small branches from the kidneys seem to enter, which coming 

 from those glands upon the mesentery of the rectum, at last open into its 

 lymphatics. At the root of the coeliac artery, the lymphatics of the lower ex- 

 tremities probably join those from the intestines. The former he had not yet 

 traced to their termination, though he had distinctly seen them on the blood- 

 vessels of the thigh ; and in one subject, which he injected, some vessels were 

 filled, contrary to the course of the lymph, from the network near the root of 



* See pi. 16 ij) the outlines, fig. 1 . — Orig. f See the same plate, fig. 2.— Orig. 



