560 PHILOSOPHICAL TRANSACTIONS. [aNNO 1769. 



be found in fish, he had not yet determined. Since he saw it in birds and in 

 the turtle, he had made indeed, some inquiries after it in fish, but hitherto 

 without success. Yet, that they are not without such vessels, he thinks, is pro- 

 bable, from considering that the lymphatics are so general, as to be found in 

 quadrupeds, birds, and amphibious animals. And from the consideration of the 

 extensiveness of this'system through so many classes of animals, he was inclined 

 to think that opinion most probable, which Dr. Hunter advanced some time be- 

 fore, when he printed his discovery on the use of those- vessels, viz. ' That the 

 lymphatics are the only absorbents.' See his Commentaries, ch. 5. 



For the sake of those who may incline to prosecute this inquiry farther, he 

 next relates the method by which these vessels may be demonstrated ; and that 

 is, having chosen a young and very lean goose, and fixed it on a table, let the 

 abdomen be opened while it is yet alive, and a ligature be passed round its me- 

 senteric vessels, as near the root of the mesentery as possible. The lacteals will 

 begin to appear near the ligature in a few minutes after it is made, especially if 

 the bird has been well fed 3 or 4 hours before the experiment. The lymphatics 

 in the neck may be shown in the same manner ; that is, by making a ligature on 

 the jugular vein at the lower part of the neck ; and to be more certain of in- 

 cluding the lymphatics, which are near it, we must take care not to pass the 

 needle too close to that vessel. When they are to be injected, they must be 

 opened at a convenient part, and a proper pipe fixed in them for that purpose. 



For the greater satisfaction of those who might think this paper worthy their 

 attention, he had prepared 2 birds, whose lymphatic systems were filled vvnth 

 quicksilver, in order to be compared with the figure : these had been shown to 

 several members of the r.s., who honoured him with their presence while the 

 subjects were fresh; and who, he flattered himself, were then satisfied with the 

 exactness of the drawing.-|- 



Explanation of Figs. 1 and 2, PL l6. 



N,B. The small letters refer to the outlines, fig. 1, and the capital letters in general refer to the 

 figure, fig. 2, except where the contrary is specified. 



A the neck; bb the clavicle divided near its middle ; c the left subclavian artery ; dd the jugular 



taken the mesentery out of the animal before he had thought of looking for these vessels, as he was 

 not at that time intent on this inquiry. The lacteals in that animal agreed with those in the bird 

 above described, in not having any mesenteric glands. From this circumstance, and from another 

 observation which he made, he was inclined to believe, that the whole system in this animal will be 

 found to agree pretty exactly with that of birds. These vessels he observed so long ago as in the 

 winter 1763 — 64. — Orig. 



t Mr, Hewson begs leave to add, that since the above paper on the lymphatic system in birds was 

 put into the hands of the secretary of the r.s., he had discovered the same system in fish; and had 

 likewise been so fortunate as to procure a turtle, whose lymphatic system he had traced out, and had 

 got delineated. An account of those dissections, with the figures, he intended to lay before the 

 Society. — Orig. 



