Sect. XXIX. 10. i. ABSORBENTS. *6 7 



It may be a matter of curiofity at leaft to obferve, that their ab~ 

 forbent vefTels feem evidently, at times, to be capable of a retro- 

 grade motion. Mr. Perault cut off a forked branch of a tree, 

 with the leaves on ; and inverting one of the forks into a veffel 

 of water, obferved, that the leaves on the other branch continu- 

 ed green much longer than thofe of a fimilar branch, cut off 

 from the fame tree ; which mews, that the water from the vef- 

 fel was carried up one part of the forked branch, by the retro- 

 grade motion of its verTels, aiid fupplied nutriment forne time to 

 the other part of the branch, which was out of the water. And 

 the celebrated Dr. Hales found, by numerous very accurate ex- 

 periments, that the fap of trees rofe upwards during the warmer 

 hours of the day, and in part defcended again during the cooler 

 ones. Vegetable Statics. 



It is well known that the branches of willows, and of many 

 other trees, will either take root in the earth or ingraft on other 

 trees, fo as to have their natural direction inverted, and yet flour* 

 ilh with vigour. 



Dr. Hope has alfo made this pleafing experiment, after the 

 manner of Hales — he has placed a forked branch, cut from one 

 tree, erecl: between two others ; then cutting off a part of the 

 bark from one fork applied it to a fimilar branch of one of the 

 trees in its vicinity •, and the fame of the other fork ; fo that a 

 t-ree is feen to grow fufpended in the air, between two other 

 trees ", which fupply their fofter friend with due nourishment., 



Miranturque novas frondes, et non fua poma. 



All thefe experiments clearly evince, that the juices of vege- 

 tables can occasionally pafs either upwards or downwards in. 

 their abforbent fyftem of veffels. 



X. Objections anfwered. 



The following experiment, at firft view, would feem to in- 

 validate this opinion of the retrograde motions of the lymphatic 

 vefTels, in fome difeafes. 



About a gallon of milk having been given to a hungry fvvine,he 

 was fuffered to live about an hour, and was then killed by a ftroke 

 or two on his head with an axe. — On opening his belly the lac- 

 teals were well feen filled with chyle ; on irritating many of 

 the branches of them with a knife, they did not appear to emp- 

 ty themfelves nattily ; but they did however carry forwards 

 their contents in a little time. 



I then pafTed a ligature round feveral branches of lacteals, 

 and irritated them much with a knife beneath the lieature, but 



couli 



