240 RETROGRADE SECT. XXIX. i. 6. 



very frequent between the inteftinal and urinary lymphatics, as 

 mentioned by Mr. Hewfon, (Phil Tranf. v. 58.) 



6. Nor do all the inteftinal abforbeflts feem to terminate in 

 the thoracic duel, as appears from fome curious experiments of 

 D. Munro, who gave madder to fome animals, having pre- 

 vioufly put a ligature on the thoracic duel:, and found their 

 bones and the ferurn of their blood coloured red. 



II. The Vafoes of tie Abforbent Syjtem may fitffer their Fluids to re- 

 gurgitate in fome Difeajes. 



1. THE many valves, which occur in the progrefs of the lym* 

 phatic and lacteal veflels, would feem infuperable obflacles to 

 the regurgitation of their contents. But as thefe valves are 

 placed in veflels, which are indued with life, and are thernfelves 

 indued with life alfo ; and are very irritable into thofe natural 

 motions, which abforb, or propel the fluids they contain -, it is 

 poflible, in fome difeafes, where thefe valves or vefleis are ftimu- 

 lated into unnatural exertions, or are become paralytic, that dur- 

 ing the diaflole of the part of the veflel to which the valve is at- 

 tached, the valve may not fo completely clofe, as to prevent the 

 relapfe of the lymph or chyle. This is rendered more probable 

 by the experiments of injecling mercury, or water, or fuet, or by 

 blowing air down thefe veflels : all which pafs the valves very 

 eafily, contrary to the natural courfe of their fluids, when the 

 veflels are thus a little forcibly dilated, as mentioned by Dr Hal* 

 ler, Elem. Phyfiol. t. iii. f. 4. 



" The valves of the thoracic duel are few, fome aflert they 

 are not more than twelve, and that they do not very acurately 

 perform their office, as they do not clofe the whole area of the 

 duel, and thence may permit chyle to repafs them downwards. 

 In living animals, however, though not always, yet more fre- 

 quently than in the dead, they prevent the chyle from returning. 

 The principal of thefe valves is that, which prefides over the in- 

 fertion of the thoracic duel:, into the fubclavian vein *, many have 

 believed this alfo to perform the office of a valve, both to admit 

 the chyle into the vein, and to preclude the blood from entering 

 the duel: , but in my opinion it is fcarcely fufficient for this pur- 

 pofe." Haller, Elem. Phyf. t. vii. p. 226. 



2. The mouths of the lymphatics feem to admit water to paf 

 through them after death, the inverted way, eafier than the nat- 

 ural one ; (ince an inverted bladder readily lets out the water 

 with which it is filled ; whence it may be inferred, that there 1*3 

 no obftacle at the mouths of thefe veflels to prevent the regurgi- 

 tation of their contained fluids, 



I 



